The columnist provided some information that fit in the limited space allotted but not nearly enough to really address the issues. For example, s/he says there are four reasons a floor can sag, exactly four:

The unfortunate truth is that there are more than four causes. Here are, in my experience, the most common:

* Improperly compacted fill material that when the house was new appeared solid, but instead, over time, compacted, taking part of the house down with it.

* Soil with a lot of organic material that over time rots and loses volume. Organic material can be roots, stumps, or anything else that once was living.

* Saturated clayey soils that change volume as they lose or gain water. Clayey soil is like a sponge, when it’s dry it wants to absorb water and get larger. When it’s wet, water can be squeezed or evaporated out resulting in shrinkage.

* Landslides, which generally only happen on sloping sites. This is where a big chunk of earth develops a failure or slip plane underground and then moves downhill. Any structure built on top will go along for the ride. Landslides can travel slowly (fractions of an inch per year) or rapidly (many feet per second.)

* Wood under attack from pests. When a portion of floor is attacked by microorganisms, termites, or other wood-eating critters, said wood will disappear taking down whatever is on top.

You can see that my list is mostly about bad soil. The author doesn’t mention soil at all.

Also, are we talking about sagging floors or sloped floors? To me a sag is a low spot in or near the middle. That’s quite a bit different than a floor that heads down but doesn’t come back up. The writer says, “I feel that I’m walking downhill…” So is that downhill to the middle of the room then back uphill? Or downhill all the way across the room?

Floors, especially 1^st-floors, rarely sag. And when they do it’s usually because bad soils are present, not because of some framing deficiency.

Let’s say, however, there really is a sag caused by bad floor framing, i.e. the foundation and soils are competent. How much sag is too much? For floors, the maximum amount of deflection (sag) per code under full load is l/240. The “l” is the member’s span in inches. So for example, if a joist’s span is 16-feet (192-inches), the maximum deflection would be 192/240 = 0.8-inch. Any 16-foot joist that deflects more than that is not in compliance with code. Now, if the joist is only 6-feet long (72-inches), the maximum code-allowed sag is 72/240 = 0.3-inch. That would hardly be noticeable.

Why wouldn’t I expect 1^st-floor joists to sag? Most span only 6 – 8 feet. These relatively short joists, even when significantly undersized, are not likely to sag much. A heavy load, such as a pool table or waterbed, will likely be spread over several joists and a couple beams, which typically wouldn’t span more than 6 or 8-feet either and also are not prone to significant sag. So as long as the soil supporting the posts and piers is competent, I wouldn’t expect much sag in a typical 1^st-floor system.

[For Gearheads Only: To make sense of the above paragraph you need to know what “undersized” really means. There are three criteria that engineers check in the design of any beam or joist: shear strength, bending strength, and deflection. A member’s adequacy has mostly to do with span. Short undersized members are more likely to fail in shear. Longer members typically have trouble with bending and deflection.  A shear failure commonly results in rupture at or near a support. Bending and deflection problems are indicated by sagging and bounciness. So long span joists (typically greater than about 14-feet) are more prone to sag or bounce, and short-span ones, if overstressed, are more likely to crack or split near a support. Going back to the above paragraph, most 1^st-floor systems are made up of short span joists and beams that if distressed would likely experience shear cracking not deflection or sagging.]

Let’s look at the author’s four causes one-by-one.

1. Improperly sized floor joists. Floor joists should be 2×10 Yellow Pine or Douglas Fir.

I just about fell out of my chair when I read this. It is a bad statement on several levels.

A. Improperly sized floor joists rarely sag. They may well be bouncy, but a sag indicates permanent deflection – a rarity. I’ve seen many more sagging ceilings than floors, mainly because ceiling joists are more likely overspanned than are floor joists.

B. Floor joists need not be 2×10, they could be anything: 2×6, round poles, 2×12, 4×8, any of dozens of manufactured I-joists (TJI is a trade name for one brand), etc. Saying a floor joist should be a 2×10 is like saying baseball is Derek Jeter. For me, baseball is the Mariners, and little league, and Willie Mays, and bringing your mitt to a ballgame, and home runs, etc. The right sized floor joist depends on loading and span, both of which can vary wildly.

C. Floor joists need not be Yellow Pine or Douglas Fir, they could be Hem Fir, Cedar, Redwood, Oak, a manufactured I-joist, you name it. There is no wrong material for a floor joist, you generally pick the most cost-efficient, code-compliant one.

Selecting the right floor joist is a pretty simple matter with good software. This link from my company’s website shows an example of how it’s done: http://www.constructioncalc.com/blog/wp-content/uploads/2009/05/example-floor-joist-9-13-051.pdf  Note that the Results Section shows both sawn lumber and I-joists at the same time – very handy.

2. The floor joists’ span between supports may be too long.

It’s true that an overspanned joist can cause problems but not likely a sag, especially with a 1^st -floor system.

3. Decay or infestation can weaken the floor joists.

Sure, but what about the subfloor, beams, and posts? Why limit decay or infestation to just joists? I think most seasoned home inspectors will tell you that rot or decay is as likely to affect the other structural components as joists.

4. Improper loading, for example a pool table or waterbed might weigh more than the floor was designed to support.

I suppose a heavy load could cause sagging but it’s not likely. While it’s true that waterbeds and pool tables are heavy, they’re not much, if at all, heavier than the code-prescribed loads to which floors should be designed. For example, a high-quality slate pool table might weigh 800 lbs, which if spread over its approximately 23 square feet, yields a unit load of about 35 pounds per square foot, easily below the code prescribed minimum of 40 psf. A waterbed that has about 8” of water in it would weigh about 42 pounds per square foot, including the wood frame. Add people and you’re at about 50 psf. While this is 20% more than code allows, it shouldn’t cause a problem with a code-compliant floor system. Why? Because wood structures built in conformance with code have a 2.5 +/-  factor of safety included. That means a 40 psf code-compliant floor could theoretically take up to 40*2.5 = 100 psf before sustaining serious damage. A waterbed is half that.

But let’s say the floor isn’t code-compliant – that if calculated would only support 20 psf. Now would we have a sag? Maybe, maybe not. It would depend on the span of the floor joists (see, For Gearheads Only, above.)

What about a sloping floor? This is one with low point(s) at perimeter wall(s) and would give the feeling of walking downhill across a room. This is a far more common problem than a sag. Almost always the cause is settlement of a perimeter footing due to bad soils – but bad soils in isolated places, not under the entire structure. The engineering term for this is “differential settlement.” A rule of thumb for older homes is that differential settlement of more than about an inch is cause for concern. Whether or not it really is a problem depends on how much more than an inch and your tolerance for walking downhill (and of course uphill when you go the other direction.) In my book GREEN FRAMING – AN ADVANCED FRAMING HOW-TO GUIDE there’s a picture of a house I call the Titanic. It’s differential settlement is about 16-inches and yet people still live there. That would be like a perpetual Stairmaster workout . Compared to such a house an inch or two differential settlement might seem like nothing.

Let’s say your house has 2-inches of differential settlement and you don’t mind the feeling of uphill and downhill. And you don’t mind trimming doors so they shut correctly, nor pencils rolling across countertops or uneven utensils in cupboards. Should you spend the money to have it fixed? The answer depends on whether the settlement is done or not. I.E., is the bad soil finished being bad?  That’s an awfully hard question to answer unless you know what’s causing the settlement. If, like in the case of the Titanic, the problem is a lot of organic material buried under one end of the house that’s been rotting for 50 years and probably will continue to rot for another 50, then a fix is in order. If on the other hand the problem is that the original builder didn’t  properly compact some of the soil when he built but that soil, over the life of the home, has self-compacted to an equilibrium point, then no, you don’t really need to fix it.

Here’re some more dubious points from the article.

The fibrous materials in wood are somewhat elastic and will stretch under tension.

Wood is very elastic and under normal loading springs right back to its original shape when live loads (people, furniture, etc.) are removed. The problem occurs when permanent loads are too great, causing overstress. In this case wood can deflect permanently, called “plastic deformation” or  “creep”. As stated before, this is most common in overspanned joists. You also see it frequently in overspanned roof rafters.

Regarding tension, tension is only part of the stress story. In any bending member there is also compression and shear. To mention one without the others is kind of like the ying without the yang, a cheeseburger without the cheese, the One Stooge.

Typical 2-by-10 floor joists, spanning 16-feet, can be expected to sag about 1/8 to 1/4 of an inch.

As we discussed earlier, a joist spanning 16-feet can be expected to sag, under full load, 3x – 4x that amount (0.8-inch) and still be in compliance with code. The maximum allowed deflection (sag) has nothing to do with the joist’s size, it is a function only of span; 0.8-inch applies to 16-foot long 2×10s, 4×6s, I-joists, whatever.

The floor system can be repaired…

What would a “fix” be? There are several ways to fix settlement. If the problem is an interior sag due to bad soil, usually the most practical remedy is to jack up the low spot and shim the post to beam connections. This may or may not be permanent depending on whether the bad soil is done settling. Meaning that you may have to repeat the process in a few years. But it’s pretty cheap, and it might work for many years. Certainly if the soil under a few posts and piers is obviously bad, it should be removed and replaced with compacted granular soil, and the footing replaced. Such operations are usually challenging because most crawl spaces don’t have a lot of room to maneuver. Still, however, these types of repairs are made regularly by nimble, unclaustrophobic people.

The best fix for any settlement involves underpinning: the installation of piles, usually helical anchors or pin piles. These are small diameter steel piles screwed or pounded into the bad ground to a depth such that they reach good soil and or develop sufficient strength to permanently hold up the structure. Installing them under a perimeter footing isn’t too big a deal as long as heavy equipment (small excavator usually) can access the settled area. You can see, I think, that attempting such a repair on a sagged portion of floor would involve driving an excavator into the house, which is not recommended, nor safe. Even small excavators weigh 3 -5 tons. Underpinning can easily cost $15,000 or more depending on the extent of lifting needed.

If a sag is caused by inadequate framing, i.e. undersized joists and or beams, usually the best remedy is to add more support in the form of new beam(s) and or new post(s). If done in the crawl space, this shouldn’t cause any ancillary problems, though as mentioned above, doing it presents certain confining challenges. If the floor in question is a 2^nd floor, new beams and posts will definitely have an effect on the living space below. Another option is to add extra joists. This can be done on any floor but if it’s the 2^nd floor you’ll have to tear off the ceiling to gain access.

The floor may need to be raised using jacks over several months before adding a new beam.

I think the author is talking about fixing plastically deformed (permanently sagged) members here. That’s the only explanation I can think of for taking several months. I suppose you could attempt it, but who has several months to drag out a repair? And even then, it’s doubtful you’d recover all of the creep. A more realistic approach would be to jack up as much as possible without causing damage then do the repair. If you don’t get it back perfectly level, so what? The house is over 50 anyway. (I’m over 50 for crying out loud.) Then again if you’re that persnickety, you probably could afford to tear the bad section out and replace it.

In summary, sagging or sloping floors can be tricky things with many possible causes and potential fixes. An excellent first step for anyone considering purchasing such a home is to hire a competent building inspector or engineer and have them give you the full scoop.

Tim Garrison of ConstructionCalc.com, is a professional engineer, author, and software producer for the building industry. Check out his latest book, “Green Framing – An Advanced Framing How-To Guide” at www.constructioncalc.com

Here is a sketch of the issue (the deflection shown is at an exaggerated scale.)

The problem did not occur at window, door, or single garage door lintels, only at the 16’ double garage door lintel. This builder uses L5×3-1/2×5/16 steel angles for all lintels.

The cracking problem is likely due to deflection (sag) of the lintel. When the lintel sags, its ends rotate upward, distressing the brick and mortar there.

I found it strange that only one size lintel was used regardless of the span. Recall from my previous writings that bending stresses and deflection go up exponentially with increased span. Meaning long span lintels should be beefier than short span lintels. And if we want to be green, we’ll use only what is required by code and no more.

Back to our 16’ lintel, what size angle should be used? The answer surprised me.

Here is how to analyze a veneer brick lintel.

The load comes from a 45-degree triangular area, which can be simplified to a uniform load 2/3 the height of the triangle. This assumes there is adequate brick above the triangle, 8” to 16” minimum, to provide resistance to arching thrust. With this assumption only the weight of the brick in the triangle will act on the lintel; the weight of the brick outside the triangle is supported by the piers on each side via arching action. If there isn’t enough brick over the triangle to achieve arching, you must include the entire weight of the brick above the lintel.

The maximum allowed deflection for any steel lintel, per the Brick Industry Association Technical Notes 31B, 5/87, is L/600. For our 16’ opening that’s 0.32”.

Using the Custom Beam feature in ProBeam™, I calculated the midspan deflection of our L5×3.5×5/16 at 2.07”, a whopping 6.5 times the maximum allowed! Also this lintel fails in bending stress by 38%.

[Technical Note. ProBeam™ and most similar software assumes the vertical leg (compression “flange”) of the angle is continuously braced against sideways buckling. With our lintel, the only practical way to accomplish this would be to connect the top of the vertical leg to the framed wall behind using masonry ties or similar. If this is not done, the lintel becomes unstable and can support very little load. I don’t know if the subject builder installs any sort of lateral bracing but if not he definitely should.]

So the L5×3.5×5/16 is grossly undersized.

I tried an L6×3.5×5/16 and found the deflection is 1.25”, still way too much.

Even an L7×4x3/8 has 0.66” deflection, much better than what we started with, but still  two times more than the brick industry recommends.

You can see that there is probably no reasonable angle that’ll calc in this application. So what to do?

One option would be to weld vertical rebar studs to the horizontal flange of the angle which are then grouted in hollow cores of brick or are mortared between bricks. This converts the angle into a composite beam: the tension component of bending resisted by the angle, the compression component by the bricks above. In this case the original L5×3.5×5/16 would probably be fine. In order for this to work correctly, the angle would have to be temporarily supported at third or quarter points until all the brick above was placed and the mortar cured.

Another option, and the one I prefer, would be to split the single, 16’ wide door opening into two, 9-foot wide openings. I.E. build a small wall pier between two 9’ doors. This reduces the load (load triangle is only 4.5’ tall vs. 8’ tall) as well as shortens the span. Now the L5×3.5×5/16 easily meets the L/600 criteria (0.18” max allowed deflection) with a sag of only 0.12”.

If neither of the above options are appealing, the builder should at least use a lintel larger than L5×3.5×5/16, which while it might not completely solve the cracking problem, would be better and safer than what they’re using now.

I’ve written about the IRC before (“When Is Engineering Required Per the 2003 IRC?” blog, www.constructioncalc.com). I’ll spare you the chore of clicking around to find that by reprinting the interesting points here:

“I think the code folks have gone overboard in their efforts to eliminate engineering of the simpler things. In fact, I believe those very efforts are the ones causing so much confusion. There are simply too many ways to build a house to say this way doesn’t need engineering but that way does. Trying to make that distinction—that line in the sand between shall be engineered and doesn’t have to be is what this hullabaloo is all about.

I, no stranger to building codes, spent more than a day researching the International Residential Code (IRC) (read: “groping desperately to unravel a hopelessly tangled pile of kite string”) and still am not sure I’ve got this issue completely nailed down. The following, I think, begins to answer the question. I’ve included code references in case some Very Brave Person wants to investigate further.”

… and then my conclusion:

“Now for the solution. I think the code folks ran awry when they invented prescriptive design. Most people aren’t even aware that prescriptive design violates most state’s engineering law, which paraphrased, states that engineering shall be performed only by engineers (also architects in some states). Deciding what beams or shear walls to use is engineering. Period. I don’t care what IRC tables tell you, still, it is engineering. Span tables are a classic example. Say you’ve got a 16 foot garage door header that you size using an IRC span table but fail to notice the footnote that says ‘only applicable to uniform distributed loads’. Most non-engineers don’t even know what this means and won’t care that a girder truss is bringing a huge point load to the mid-span of their header, making it grossly undersized.

I prefer the good old days when the code simply described minimum standards and it was up to designers and code officials to decide when engineering was needed and when not. This required some basic understanding of the code and common sense. I think today’s codes strive extravagantly to eliminate any possibility of someone actually engaging their brain and using common sense. I’m a big fan of common sense. You see, as soon as you try to define things so precisely, so exactly, that common sense is no longer needed, two things happen: 1) Your descriptions become so dense and perplexing, no one can understand them; and 2) People disengage their brains, throwing any attempt at common sense out the window.”

All that was about the 2003 IRC. Now, two code cycles later, we’re facing the 2009. Do you think the code writers paid any attention to me when they concocted this new and improved quagmire? No, they did not.

Rather than paring down and streamlining, they packed in yet more gobbledygook. Take for example the wind and earthquake design sections. The new code greatly expanded these with the intent, I think, to allow all comers to perform lateral analysis and design.

I’m in the structural software business and here’s the feedback I get most often: “Tim, I love your programs because they’re so easy to use. Why don’t you produce one for lateral design? You’d be rich!” My answer today is the same as it’s been for 15 years: “Becoming rich would be fine, however, lateral design is just too complicated. There’s too much judgment involved. To get it right you’d spend more time inputting than if you just did it longhand.”

Yesterday’s instructor, Tim DeVries, a friend and top notch building official, did a fantastic job. He devoted nearly half of the class to the lateral design sections, which is saying something considering all the changes to the energy code, ingress / egress, and other sections. And at the end I’m pretty sure most attendees were significantly befuddled about lateral design. Not because they’re dense or Tim did a poor job, no, quite the contrary, because it’s just too darned complex.

The intent of the IRC is to bypass professional architects and engineers – to allow anyone to design their own residential structure using prescriptive methods. Actually, I’m good with that premise. I’m all for empowerment. However, I strongly believe that wind and earthquake design does not lend itself to prescriptive methods. The alternative is to hire an engineer who, if he is worth his salt, will not shoot himself in the foot with the IRC but instead use the IBC (International Building Code) and thereby save the project a lot of money in the long run.

As I said previously, any one-size-fits-all prescriptive standard will, by necessity, be overly conservative. In these lean and green times, who can afford that?

…Well, the honeymoon is over: in many jurisdictions local building officials refuse to approve a plan without an engineer’s stamp, even though it’s been designed using the prescriptive tables in the IRC. From snow loads to soils to foundations, either because of their lack of understanding of the code or unwillingness to accept liability, this issue has created a disconnect with builders and code officials. Unnecessary engineering is adding to the cost of the house (both in the fees for services and materials for over-engineering), delaying production time and quite frankly is often looked upon as a ‘nuisance’ by engineers, who place these small residential projects at the bottom of their priority list…

… Any insights, help or direction you could provide would be greatly appreciated. 

Jan Rohila, Education Program Director

Building Industry Association of Washington

In a nutshell, this issue boils down to: When is engineering required and when not? As far as being a nuisance, shame on any engineer who projects that sentiment. That would be like a builder considering nailing boards together a nuisance. Yes, some boards are easier to nail than others, but that’s what builders are for, for crying out loud.

I think the code folks have gone overboard in their efforts to eliminate engineering of the simpler things. In fact, I believe those very efforts are the ones causing so much confusion. There are simply too many ways to build a house to say this way doesn’t need engineering but that way does. Trying to make that distinction—that line in the sand between shall be engineered and doesn’t have to be is what this hullabaloo is all about. What is the solution? I have an idea, but you’ll have to slog through the rest of this column first to get to it.

I, no stranger to building codes, spent more than a day researching the International Residential Code (IRC) (read: “groping desperately to unravel a hopelessly tangled pile of kite string”) and still am not sure I’ve got this issue completely nailed down. The following, I think, begins to answer the question. I’ve included code references in case some Very Brave Person wants to investigate further.

IRC vs. IBC. Right out of the chute, there can be confusion as to which code to use. The below Scope paragraph describes when the IRC can be used. However, the International Building Code (IBC) has many similar sections and lots of its own prescriptive requirements. One would hope that the prescriptive requirements in both codes are the same, which I believe is the case, though I didn’t specifically check them all.

To be clear, this article addresses only the 2003 IRC prescriptive requirements.

Scope. The IRC applies only to detached one-family, two-family (duplexes), and multiple single-family (townhouse) structures, three stories and less in height. Anything outside that definition must use the International Building Code [R101.2].

Conventional Construction. To evade engineering, the building, from stem to stern, must be “conventional construction”; i.e. in compliance with the structural chapters of the IRC [chapters 4,5,6 and 8 primarily]. This includes, among many other things, certain minimum amounts of shear walls—both exterior and interior in many cases—and proper connection of them to foundations, floors, and roofs.

If your overall building qualifies to use the IRC but certain structural elements aren’t “conventional”, then you only have to engineer the unconventional part(s), not the entire structure [R301.1.3].

Wind. If your structure is located where basic wind speeds are 110 mph or greater per the IRC’s map [Figure R301.2(4)], you can’t use the IRC. You’re instead directed to one of four other publications (good luck finding them). Concrete construction is an exception here—you can still use the IRC for formed concrete and Insulated Concrete Form (ICF) construction in wind areas up to 150 mph [R612.1, R611.2 and R301.2.1.1].

Wind Exposure. Surprising, to me at least, is that the requirement for engineering doesn’t depend on wind exposure. So it doesn’t matter whether you’re in exposure A (very well protected from the wind) or exposure D (on the naked shore of an ocean or other large water body), the only thing about wind triggering engineering is basic wind speed. [R301.2.1.4]

110 MPH Wind. Areas of 110 mph or greater winds generally include Alaska’s seaboard and the southern – eastern seaboards (from Texas to Rhode Island). Most of the continental U.S. is in the 85-90 mph region [Figure R301.2(4)].

Seismic Design Category. Engineering is required if you are in seismic design category E, usually [R301.2.2]. The other design categories—the ones that don’t trigger engineering—are, from mildest to strongest: A, B, C, D1, and D2. If you are in category E and you can get an expert to say you’re not, then you may still get out of engineering by being demoted to D2. Or, if you’re in category E and you design a plain plywood box with no “irregularities” (see below), you may again avoid engineering by demoting to D2. [R301.2.2.1.2].

How To Determine Seismic Design Category. The handy map in the IRC [Figure R301.2(2)] shows seismic design categories for the U.S., including Hawaii and Alaska. However, it assumes a site class of “D”. But how do you know if you really are in site class D? Or, for that matter, what is site class D? Unfortunately, the IRC doesn’t give you either answer—it refers you to the IBC. Great.

Site class has to do with soil type. If your soils are stiff, dense, or rock, you’re okay with site class D. But if your soils are soft or spongy, you’re site class E or F, and now you can’t use the IRC maps to determine seismic design category—you need to hire an engineer. Cripes!

Seismic E. Seismic E areas generally include the west coast, the Sierra Nevada mountains, Hawaii (south part of the big island only), isolated pockets in the Rockies (eastern Idaho, western Wyoming, and northern Utah), southern Alaska, and a pocket along the Mississippi River in the western Tennessee, southeastern Missouri area [Figure R301.2(2)]. But, again, this is predicated on soil type.

Seismic Limitations – Dead Weight. If you use really heavy building materials for roofs, floors, or walls, engineering for seismic design will be required. Standard residential construction, including masonry and ICF, generally do not fall into this category [R301.2.2.2.1].

Seismic Limitations – Irregular Buildings in Seismic Design Categories C, D1, and D2. If your building has any of the following irregularities and you’re in C, D1, or D2, engineering is required [R301.2.2.2.2]:

• Shear walls don’t line up vertically from foundation to roof. An example might be a 2^nd floor exterior wall cantilevered beyond the exterior wall below it. Certain exceptions apply for mildly cantilevered or set-in wood framed walls.
• A portion of roof or floor is not supported by a shear wall. An example could be a portion of house supported on posts. There is an exception for projections of 6’ or less.
• The end of an upper floor shear wall occurs over an opening in the shear wall below. An example cold be a 2^nd floor shear wall that ends over the middle of a garage door below. Exceptions abound.
• There is an opening in a floor or roof that exceeds 12 feet in any dimension, or is greater than half the roof or floor’s smallest dimension. An example could be a very large skylight or a large opening in a 2^nd floor to accommodate stairs.
• Split level floors, a.k.a. vertically offset floors. Basically, if each level of floor has shear walls all the way around below, or if the floors are overlapped and tied together well, you could be exempted from this.
• Shear walls are not at right angles. This could apply to a house with a 45 degree V-shaped footprint , or any other non-90 degree exterior wall arrangement.
• Above grade stick-frame shear walls are mixed with masonry or concrete construction. However, masonry or concrete fireplaces and brick veneer don’t count, i.e. they’re exceptions. An example could be a mostly stick-framed house that has a window wall of ICF. This is the only irregularity that causes the entire affected story(ies) to be engineered.

Snow Load. Buildings located where ground snow load exceeds 70 pounds per square foot (psf) are required to be engineered [R301.2.3].

Floodway. Buildings located in floodways, as designated by the local building department, may not be designed per the IRC—they must follow IBC regulations. Note, this is different than being in a floodplain—which is allowed under the IRC without engineering [R301.2.4].

Story Height. First of all, understand that there is a difference between story height and maximum stud length. The IRC’s definitions [Chapter 2] tell us story height is a floor-to-floor distance. But in Chapter 3, story height is defined as stud height plus up to 16” of floor framing. Make sure you and your code official interpret this correctly.

The IRC is more restrictive about story height than stud height of certain individual walls. For example, is it possible to have a story height of 10 feet but also have a 20 foot balloon framed entry wall, without engineering.

Weaving one’s way through the IRC’s spaghettian layout to get to the bottom of this story height issue is no simple matter [R301.3, Table R602.3(5), and Table R602.3.1]. Here’s the upshot.

• Wood Framed Walls. Maximum story height without engineering equates to 10 foot studs plus up to 16 inches of floor framing. However, there is an exception allowing 12 foot studs if you pump up shear wall requirements 20%.

Now, certain wall’s stud heights can go all the way to 24 feet without engineering, if wind speed is less than 100 mph, and you’re in seismic category A,B,C, or D1, and you follow the spacing and footnotes in Table R602.3.1. Regardless, the story height must not exceed that described in the above paragraph.

• Steel Studs. Maximum story height without engineering equates to 10 foot steel studs plus up to 16 inches of floor framing. I found no exceptions.
• Masonry Walls. Maximum story height without engineering equates to a floor to ceiling height of 12 feet plus up to 16 inches of floor system. Gable ends can extend another 8 feet without engineering.
• ICF (Insulated Concrete Forms). Maximum story height without engineering equates to a floor to ceiling height of 10 feet plus up to 16 inches of floor system. Maximum number of stories above grade without engineering is two [R611.2].

Construction on Fill. Engineering is required for fill soils under footings or foundations [R401.2].

There’s more prescriptive stuff in this code, but the above are the structural major-ticket-items. As I alluded to earlier, finding answers here is kind of like capturing the snitch in Harry Potter’s quiddich: The snitch, very hard to see in the first place, flits and darts about while at the same time bludger balls barrel recklessly around aiming to bodily remove you from your broomstick.

Now for the solution. I think the code folks ran awry when they invented prescriptive design. Most people aren’t even aware that prescriptive design violates most state’s engineering law, which paraphrased, states that engineering shall be performed only by engineers (also architects in some states). Deciding what beams or shear walls to use is engineering. Period. I don’t care what IRC tables tell you, still, it is engineering. Span tables are a classic example. Say you’ve got a 16 foot garage door header that you size using an IRC span table but fail to notice the footnote that says only applicable to uniform distributed loads. Most non-engineers don’t even know what this means and won’t care that a girder truss is bringing a huge point load to the mid-span of their header, making it grossly undersized.

I prefer the good old days when the code simply described minimum standards and it was up to designers and code officials to decide when engineering was needed and when not. This required some basic understanding of the code, and common sense. I think today’s codes strive extravagantly to eliminate any possibility of someone actually engaging their brain and using common sense. I’m a big fan of common sense. You see, as soon as you try to define things so precisely, so exactly, that common sense is no longer needed, two things happen: 1) Your descriptions become so dense and perplexing, no one can understand them; and 2) People disengage their brains, throwing any attempt at common sense out the window.

Probably very few code writers will agree with the above, so here is another idea. How about a computer program that lets you input the type of structure you’re planning and where it will be located, then it spits out appropriate limitations and restrictions. Although I’m in the software business, this is a bit more ambitious than I would wish to tackle. If someone else wants to beat me to the punch, please do.

Tim Garrison of ConstructionCalc.com, is a professional engineer, author, and software producer for the building industry. Check out his latest book, “Cracks, Sags, and Dimwits-Lessons to Build On” at www.constructioncalc.com

Dear Builder’s Engineer,

My house was built in the early ‘70s, using 2×6 rafters spanning 13 feet between ridge board and wall. I live in New York State with a good-sized snow load. The roof has developed a sag between the ridge line and the rafter tails. I attribute that to the rafters being undersized and sagging in the middle. The sag is not horrible; I would guess it’s about an inch, maybe a little more. Still, I would like to do something now rather than wait to see if it gets worse.

A few details:

• roof pitch is 4 on 12
• a plain ranch style house…no hips or valleys…just front and back
• rafters are nailed directly to the ceiling joists
• rafters and joists are 2×6

I’m wondering if collar ties would help. I could take 12-foot 2×6’s and position them underneath the paired, opposing rafters, miter the tie ends to fit under the rafters and then use tie plates or gang nail plates to attach the ties to the rafters. I’ve read that is stronger than just nailing the collar tie to the side of the rafter. I thought that it would be best to get the collar ties supporting the midpoint of the rafter or as close as possible, that’s why I thought 12-foot length collar ties would be better.

Any thoughts or suggestions would be appreciated.

Daniel in NY

 Dear Daniel,

Following is a sketch of your roof framing as I understand it. I analyzed this using a computer and the following assumptions:

• Snow load = 35 psf (pounds per square foot)
• Dead load from comp roofing and self-weight of framing = 15 psf
• Spacing of rafters = 2 feet

First, a little theory:

Truss vs. Rafter. There are big differences between rafters and trusses. A rafter bears at both ends; typically on a wall at the low end and on a ridge beam at the high end. There is no outward thrust at the low end of a rafter.

But what about a rafter that really isn’t one? I’m speaking of a sloping “rafter” with a pitch of 2:12 or greater, with no ridge beam—usually a puny 1x or 2x instead—and no connection to a ceiling joist, truss bottom chord, or other horizontally-restraining member at the low end. If you’ve got this, you’ve got trouble. Without the support of a sturdy ridge beam at the high end, there is nothing to keep that high end from going down. The low end can’t go down because it’s sitting on a wall providing vertical support, so when the ridge sags, the low end must move outward. Bad, bad situation. At the end of this chapter is a case study exploring a fix for such a “non-rafter” system.

The absence of a beefy ridge beam is fairly common, but in such a case, the low end of each (rafter) must be connected to some other member providing horizontal restraint, such as a ceiling joist. We call this connection the heel, and the overall system a truss. In this case, the rafter is no longer called a rafter, but a top chord.

A triangular truss has very large forces at each heel. It is the heel connection that keeps the top chord’s low end from moving outward. Also, the top chord of a truss has two kinds of stresses: bending and compression; whereas a rafter has only one: bending. Basically, a triangular truss has to work very hard because it is paying the price of a long span with no interior support.

So whenever you come upon a distressed truss, the best remedy is to add interior support(s), thus lessening the span and member stresses. You can bolster trusses, but without additional support, you’re simply spreading stress around—stress that must still be dealt with, and which becomes troublesome, particularly at connection points.

Let’s look at the truss in question. Note the 2×6 top chord is 217 percent overstressed and will sag 1.6 inches under a full snow load. The force at each heel is 1,700 pounds which requires twelve 16d nails to keep the top chord from moving outward. It is a miracle this roof hasn’t imploded.

Can anyone tell me how to cram twelve 16d’s into the small overlap space where the top chord and bottom chord (ceiling joist) come together? I think if you tried, you’d massacre the wood so badly, none would be left to hold the nails. It is for this very reason that gang-nail plates were invented.

Everyone wants to fix their sagging trusses with collar ties, presumably because they’re relatively easy to install. Here is the subject truss with a collar tie at the top chord mid-span.

Now the top chord is in better shape: only 70 percent overstressed with 0.82-inch sag. But look at the connections. Each collar tie connection point must resist 2,100 pounds of force, which would require fourteen 16d nails. Can’t be done. Also, the collar tie is in such compression that a 2x won’t cut it; a 4x is needed. But even more troubling is what happens at the heel. The top chord/bottom chord force has ballooned to a whopping 2,850 pounds. No way to make this connection. In short, the collar tie took load from the top chord and shuffled it around to other places, but those other places can’t take it.

When this column originally ran, I suggested the following upgrade: sister 2×6’s on to the existing rafters, like so:

This reduces the stress and sag of the top chord by half, but more importantly, does not increase the load on the heel connection. Note the sistered 2×6’s need only cover the middle 70 percent +/- of the rafter, not the entire span. This is because the sag is a bending problem (as opposed to shear, tension, or compression), which occurs in the middle two-thirds or so of the top chord. Bending stresses go to zero at the top chord ends; thus, no bolstering is needed there. I like this solution better than the collar tie. For more on beam theory, see my book, Basic Structural Concepts for the Non-Engineer, available at www.constructioncalc.com.

If we really want to solve the problem, we’ll find additional interior support. Like so:

Note that this completely solves the sag and top chord overstress problems, and it hugely reduces the heel connection force. The rub is making sure the interior support can truly take the load. In our example we’re adding about 600 pounds per foot (that comes from 1,200 pounds per truss, which are spaced every two feet) to the interior supporting wall—no small amount. If this wall has a continuous footing below it, it is probably okay. If this wall has large openings in it, those must be spanned with a beam, and the ends of said beam(s) need proper support all the way to a proper footing.

I once was involved in an old schoolhouse with a badly sagging roof. It was a hip system, about 8:12 pitch. There were no trusses, it was a rafter system; but amazingly, there were no beams at ridges, hips, or valleys. So the outward thrust at rafter heels had to be taken by the walls, but they couldn’t, so there were big outward bulges in the exterior walls. It is a miracle this building didn’t implode in one of our snowy northwest winters—a testament to the toughness of wood. Here is a sketch showing the problem and the fix (shaded).

We did our best to winch the exterior walls back to plumb and jack the roof back up. Then we installed a series of beams directly supporting the rafters, ridges, hips, and valleys. Of course, the new beams had to bear on something, so we positioned them over existing walls below and then retrofitted footings in the crawl space where the new loads came down. Interestingly, the contractor’s first suggestion was to install collar ties as a fix. No, no, no.

In summary, there is no easy fix for an improperly designed roof framing system. Collar ties are almost never recommended. Rather, find a way to add interior support, taking loads all the way to a good footing. And certainly, the best alternative is to design it right the first time.

 “Tim,” he carped, “I’ve got a new high-end home project in San Francisco that an engineer WAY overdesigned. This guy spec’d so much rebar, there’s no room left for the concrete. No contractor will bid the job – and that’s saying something in these tough times. He’s killed the project! I’d call the joker but I’m so hacked right now I’d probably say something I shouldn’t. And besides, you know how certain engineers can never be wrong? I’m in a bad way here. Would you be interested in re-engineering this thing?”

 Red lights and flags went up in my head. I’ve been down this road before. Were I to say yes, here’s what would likely happen. I’d redo the job and find that the other engineer didn’t know what he was doing. Maybe he’s some government paper pusher moonlighting – it happens all the time. Anyway, when he gets wind that my design used less than half the  rebar and 2/3 the concrete, to save face, he attacks me. Now I have to defend my design to the State Board, or, I have to report him to the State Board for practicing outside his area of expertise (it’s law, by the way, that a licensed engineer must rat out any other engineer who violates the state’s ethics rules.)

 On the other hand, it really gripes me to hear of engineers overdesigning. Not only is it anti-green, it’s hard on projects and gives our profession a black eye.

“Tell you what, Sty,” I said. “I’ll look into it for you. What’s this guy’s name and who is the architect?”

“The engineer’s name is Tomache Steele and the architect is Cary Granite. Here are their phone numbers.”

I called the architect first. After a few pleasantries, I said, “I don’t know if I can help or not, Cary, but the first step is for me to look at the plans. Can you email them over please?”

“No problem,” he said. “I’ll also pdf you the calcs. Tomache’s contact information is there but good luck talking to him. It usually takes a few days to get a call back.”

“So you’ve worked with him before?”

“Yes, several times. Mostly because his fees are low. Someday I’ll learn my lesson though and stop using him. Not only are his designs over-engineered, he’s a terrible communicator, and he’s always several weeks late. Grrrr.”

“Roger that. I’ll see what I can do.”

“How soon can you look at this?” he said. “We’re just about through plan review with the city and we’re thinking to take the revised design back to them after we have a permit in hand.”

“My schedule is pretty open,” I said. “I’ll get back to you as soon as I know something.”

The plans popped up on my computer a few minutes later. I’ve engineered many concrete projects over the years, a dozen or more being ICF, and I have never seen such flagrant overkill. Truly, there was at least double the rebar needed and the walls could have been two inches thinner. Greenhorn, I thought. He’s probably some bureaucrat with no real-world experience locked in a sea of cubicles in some non-descript low-rise.

Then I looked at the calcs.

First, the letterhead identified a small, local private engineering firm. So much for my bureaucrat-in-a-cubicle theory. Second, I was shocked to see “S.E.” under Tomache’s name. This guy is a full-blown structural engineer! If you’re unfamiliar with the title, it means he has not only taken and passed his professional engineer’s license exam, he’s also taken and passed a 2^nd exam, a two-day brain buster akin to the bar exam for lawyers. Very few who take it pass it. In fact, only a select few qualify to take the S.E. Having the letters “S.E.” behind your name is a big deal – it places you in elite company among engineers.

The calcs themselves were beyond professional, 100% typed – nothing by hand, with computer-generated sketches of every structural element. And thorough? Holy smokes, the guy took more pages just coming up with one seismic force than some engineers take designing an entire building.

Top it all off with the fact that the local jurisdiction is the City of San Francisco. Which, last time I did a project there, had an S.E. or two on staff. So Tomache’s calcs have likely already been reviewed by one of his brethren, who would likely frown on a lowly P.E. (me) correcting them.

This was not at all what I had anticipated.

What to do? What would you do?

Here’s what I did. I picked up the phone and called Tomache. In my way of thinking, the best possible outcome would be for him to recognize his overly conservative design and back it down some. There is a name for that, actually, it’s called “value engineering.” And it’s pretty common. In fact certain consultants make their living at it – they’re essentially hired guns who analyze projects and recommend alternate methods to save money. My challenge was to do precisely that without offending.

It took three days and several attempts, but finally Tomache called me back. The conversation went better than I expected. He spent several minutes defensively explaining his rationale for all that rebar, particularly in the two walls with all the windows. I listened patiently then made a few calm suggestions which he conceded were worth revisiting, and that possibly he’d been a bit conservative.

In the end, his redesign was not as efficient as if another engineer had done it. Still too much concrete and steel, in my opinion. But no one got sued, contractors will bid it, and it will be built. Someday the owners will occupy their nice new ICF home, blissfully ignorant of all this behind-the-scenes drama and that they paid quite a bit more than they should have. Was it the best possible outcome? Maybe.

This, for the most part true, tale illuminates several takeaways worth restating:

* You generally get what you pay for.

* Bad design will cost far more in construction than you saved up front in fees.

* A person’s credentials don’t always equate to competence.

* Engineers are not created equally. Give any two the same set of plans and they’ll produce two very different designs. This, regardless of the fact that both engineers are bound by the same code.

* Sometimes the best solution is not a redo by someone else. Try communication first, always.

* Value engineering can be a very good idea. Even if it costs money. Many times the savings realized more than cover the cost, plus it puts another set of qualified eyes on the project and that’s never a bad thing.

What about me – how did I make out? Well, monetarily, I didn’t. But I’m okay eating a couple hours to help a distressed project. Also there’s the hope that this architect and sales rep will remember me before hiring Tomache next time. I call it goodwill marketing.

Thanks in advance if you choose to accept this mission.

Rick Krause

TIM’S RESPONSE

Hi Rick,

Thanks for asking. Attached is the printout for your floor joist.  You could use 2, 2×8 at 16″ OC and be safe, but I guarantee the floor will be bouncy. If you used 12″ OC, it would still be bouncy. I understand your height constraint and so you might be okay with the bounciness as a tradeoff for the headroom of 2×8 joists.

If you wanted a stiff floor you’d have to use deeper joists. The analysis in ProBeam would be exactly the same except you’d pump up the deflection criteria to say L/600 and L/480.

Thanks again.

Example Flr Joist ProBeam 11-4-09

Building codes are a relatively new invention. The first widely-accepted building code in the U.S. was written in the early 1900s. Today’s building code, the International Building Code (IBC), has its roots in the Uniform Building Code (UBC) which was first published in 1927. Over the years many local jurisdictions adopted building codes but many did not. Even today there are jurisdictions in the U.S. that do not issue building permits nor require adherence to any building code.

Where I live in western Washington, building codes are strictly enforced for any structure from a shed to a fence to a sky scraper. Around here it’s unthinkable that a house might be designed by a non-professional and built without a building permit.

But where my brother lives in Kansas, there are no such requirements. Draw up your plans on a napkin, grab your hammer and go. There are lots of places like that in our country today.

So in America we’ve got quite a mix-mash of structures. A few that meet current codes but many, many that don’t.

I took some photographs the other day of old buildings in my county.

The first one, I call the Titanic. This house is probably at least 50-years-old and as you can see has settled terribly. The house is likely built partially over an old slough that was filled with logs and other debris. The part built over the slough embankments has not settled but the part built over the fill-debris has. This is called differential settlement. Incredibly, people still live in this house.

The next structure is a 75+ year-old commercial building. By today’s standards it contains not a single shear wall nor a horizontal diaphragm. It is listing about a foot out of plumb, yet there it stands.

Here is a very large barn, probably 50+ years old. Note how huge its wind sail area (roof) is. Also you can see that it is located in the middle of an open valley with no trees or other buildings to shield it from the wind. The gable end walls are mostly door openings, and the wood panels in between don’t come close to any sort of legal shear wall. The roof isn’t a legitimate diaphragm. There’s a two-foot sag in the roof at the eaves. Yet year after year, winter after winter, storm after storm, this barn continues to serve.

According to its historic placard, this building was constructed in 1890. It has undergone an extensive tenant improvement, but other than new windows and doors, the exterior walls, floor and roof framing are original. It is built partially over a salt water channel, supported on timber piers. The horizontal siding on the long walls shows settlement up to a foot in several areas. The above photo is the rear wall. Note all the windows and doors (read: no shear panels.)

The front wall is pretty much the same: all windows; which count for nothing in resisting lateral (wind and earthquake) loads. Here is what this wall looks like from the inside:

This is also the front wall, about mid-height.

This wall is constructed of horizontal siding attached to 2×4 studs. Not one shear panel, holdown, or hurricane clip.

Roof framing is 2×6 rafters, originally spanning 20+ feet. There is no ridge beam. I’d go so far as saying there isn’t one code-compliant piece of lumber or connection in this entire building. And in fact most structural elements are overstressed, according to current code, by several hundred percent.

In its 119-year life, why hasn’t this building imploded or blown over?

This last building was also built in 1890. One corner (the one by the streetlight) has settled at least six-inches. But that’s not what makes this one of the most dangerous buildings in the county. The front wall is all glass. No shear walls, no portal frames, no buttress walls, nothing. And the next parallel interior wall is some 30-feet back into the building. As the one corner sinks, the building tilts causing racking (shear) stress on the window wall. Should a window break or crack there is a real possibility that this building would fall over sideways – I’ve seen it happen to a building of similar construction in a nearby town. Yet, this building stands.

All of the aforementioned structures have lived through snow accumulation of several feet, howling wind storms, and earthquakes.

All across America and the world are buildings that don’t come close to meeting current code. It usually takes a hurricane, tornado, severe neglect, freakish snow storm, or 7+ magnitude earthquake to bring them down. And even then many survive.

So what’s the point?

The point is that things not built to code are usually plenty strong and those that are built to code are vastly stronger than they need to be in most cases.

If you live in a jurisdiction that has building codes and enforces them, you don’t have a choice but to comply with those codes. But you don’t need to overbuild.

Let me say that again. Our building codes contain so much factor of safety, no one should ever feel compelled to exceed them. The grossly non-code-compliant buildings on the previous pages, in my opinion, provides stout testimonial.

Our industry should be actively searching for ways to trim our designs so that they just comply with code and no more. If we build stronger than code we’re literally throwing away money and effort. And we’re not building green.

This book is about minimal, yet code-compliant, structural design. Green design. The trick is understanding the underlying structural concepts: where loads come from; where they go; and how they’re resisted. With that knowledge, we can maximize efficiency and save money.

General

Green framing, advanced framing, frugal framing – call it what you will – but in the end it’s all about saving money and resources. 

There are lots of ways build-green can be incorporated into a structure: energy efficient appliances and fixtures, special doors and windows, more and better insulation, smart site planning and earthwork to name a few. This chapter is not about those, it’s about stick framing methods – strategies that conserve lumber, concrete, and steel, not to mention the manpower associated with their installation.  

A Little Background

Billions of dollars are wasted every year in overbuilt structures. Not only have I been a framer and been guilty of many wasteful practices myself, I see the inefficiency and waste every time I walk a jobsite. Some examples:

• Too-big beams and headers
• Too much blocking
• Too many studs
• Too many trimmers and king studs
• Too many cripples
• Too many holdowns
• Too many shear walls
• Too many posts and piers in crawlspaces

How did we get billion-dollar-wasteful?

Here’s how:

• Building codes have gotten more and more restrictive over the years. They’ve also become so bloated and difficult to use most building industry folks avoid them like the dentist. The result is we’re gun-shy about being efficient. The accepted code mentality is “more is better.” So when we aren’t sure, we throw in more. Tons and tons and tons more. We may as well throw most of that “more” into a landfill; it does no good whatsoever. And in fact, a lot of the time it is counter-productive: more wood, concrete, and steel means less insulation; and more weight adds proportionally to seismic forces. There is no code-incentive for efficiency.
• Most builders have no training in basic structural theory. Its tough to question a more-is-better mentality when you’re not really sure of the underlying concepts. How do builders learn their trade? From other builders; who learned from other builders before them, and so on. Where’s the formal structural training? It’s never been there.
• Most architects and designers don’t receive enough structural training to make them experts. They generally know enough to size a beam or post but to really sharpen the pencil and get efficient puts them out of their comfort zone. And why go there when the building code doesn’t require or encourage it?
• Most engineers are more worried about liability than saving someone else’s money (the owner’s). They have little incentive to produce efficient designs. To an engineer, more is safer. It takes extra time to explore green alternatives, and with engineers especially, time equals money. Why should an engineer cost himself more money, incur more liability, and go against the grain of the code, especially when he can snow job the owner as to how massively strong he’s made the building? Owners don’t know to ask the right questions, and the engineer grins all the way to the cruise ship.
• Building officials have zero incentive to enforce or even encourage green techniques. They answer to the building code (see first bullet point.)
• Private industry has no incentive to do anything either. Would you expect lumber companies, framing hardware companies, or concrete companies to stand up and start shouting for less use of their products?  What has happened, however, is that new, efficient mousetraps in the form of SIPs (Structural Insulated Panels) and ICFs (Insulated Concrete Forms) have sprung up. Those are terrific products and I endorse them heartily. But they do nothing for the vast majority of builders who use traditional methods and materials.

It’s a racket and vicious cycle that desperately needs fixing. The first step is education. Once builders, designers, architects, and code officials understand what’s going on and that the solutions are attainable by them, they will start putting pressure on the engineers. Or, better yet, they’ll start implementing the designs themselves.

In the BC days (Before Computers) it was unreasonable to expect non-engineers to perform structural calculations. But with the advent of computers and user-friendly software, now anyone can do basic structural design.

Throughout this chapter we’ll use my company’s software, ConstructionCalc, for our green designs. If you’re new to structural design aids (span tables or software) you’ll probably want to bone up at www.constructioncalc.com, checking out the free examples and white papers.

To keep things popping along, I’ll assume you know the basics. Again, if you need a little background please avail yourself of the freebies at www.constructioncalc.com.

(to be continued)

Copyright, August, 2009, Tim K. Garrison, P.E. All rights reserved.

Ask the International Building Code (IBC), however, about an old barn and the response will not be so nostalgic: “That derelict collection of sticks is a disgrace to human progress! There isn’t one part or piece that complies with my dictates! The atrocity must die!”

Following is just such an example, from the Skagit Valley Herald, July, 2009 by Elliot Wilson, photos by Mark Malijan. Here is the link: http://www.goskagit.com/home/article/saving_skagits_barns. According to the article the Prevedell barn was built in 1915. It recently received a Heritage Barn Preservation Initiative grant. That money plus the owner’s matching funds were spent patching up the foundation and putting on a new roof. Doors, windows, studs and siding were also replaced.

The Prevedell Barn, built 1915.

If you look at the exterior photo carefully, you’ll notice that the barn is in an open field. Meaning that it is subjected to a relatively severe wind exposure, category “C” (open terrain for at least 1/2 mile) . I did a rough calculation and estimate that using today’s code the wind load on this barn would be around 50,000 lbs of sideways force. That’s 22.5 tons racking the building over. And the net uplift (total uplift minus dead weight of roof) would approach 21,000 lbs, some 10.8 tons prying the roof off. This barn does not have one shear wall, one holdown, a drag strut, or even a horizontal diaphragm. There isn’t a single hurricane clip or tie strap. And for 90 of its 94 years it had very little foundation, with only a handful, if any, anchor bolts.

Look at the interior photo and you’ll note that there is no ridge beam. There are no steel plates, bolted gussets, beam hangers, column caps, or any other framing hardware. Rafters appear to be 2×6’s at 2’ spacing, spanning some 20-feet. There are poles and beams holding up the rafters which are connected together with drift pins or dowels. If I calc’d any of those structural members per today’s code they would all fail by at least 100% and in some cases 1,000% or more.

In the same photo, the owner is standing on a hay loft at the eaves level. You can see that it’s loaded with hay. Hay is heavy. Much more than the rough sawn rafters and beams should be able to hold, according to code.

This old barn is built just like the ones on my family’s ranch. One time my dad was cleaning the manure out of our hay barn with his tractor and knocked out a post. There was no beam spanning to the adjacent posts, just a double 2×4 top plate. The roof sagged but didn’t come down. It sat that way for several years, until my dad got around to installing a new post. A few years later some cows knocked out another post. That one was never replaced. The barn still stands today.

I recently did a structural analysis of an old barn that had been converted to migrant worker housing. The owner built a three-story complex of apartments under the roof without a permit and was ratted out by a neighbor. It was my job to verify that the entire shebang was in conformance with the International Building Code (IBC). To begin with, just like all old barns, nothing original came close to meeting code. The apartments actually added a lot of lateral resistance but they, too, did not meet code. Truth be told, my job was impossible. The only way to ensure code compliance was to tear it all down and start over. That would have been infeasible for the owner and would have put a dozen families on the street. So I rolled up my sleeves and did my best, trying, as we used to say on the ranch, to make ice cream out of  pig poop.

If that barn would have asked me why, why was I adding all those shear walls, brackets, clips, and all that lumber, I would have been hard pressed to give a sensible answer. I’m well aware that it had been there 50 years and with a little maintenance it would be there 50 more.

If old barns could talk, the Prevedell Barn might offer keen opinion on the travesty that is our IBC. It might say something like, “Now that code there… shee! It ain’t worth the paper it’s writ on. Fer one thing it’s so confounding a feller can’t make heads ner tails of it. And even if he could, with all the concrete and steel it throws around, why, it’s sorta’ like killing flies with a sledgehammer.”

Copyright August 3, 2009. All rights reserved.

Tim Garrison, P.E., The Builder’s Engineer™

Author of “Cracks, Sags, and Dimwits – Lessons to Build On” and “Structural Concepts for the Non-Engineer” available at www.ConstructionCalc.com