- The designer has no clue about lateral (wind and earthquake) loading and its effect on a structure. In this scenario, the architect or designer makes his best guess where shear walls should go, the number of and location of holdowns, anchor bolts, etc. No engineer is hired to do it right; instead, the designer depends on a building official to correct his handiwork. Unfortunately, most building officials don’t know any more about lateral design than the designer, so the final product is woefully wrong. It is either overdone or underdone — too expensive or just plain dangerous.
- An engineer's hired, but the engineer is a rookie. I can tell you from first-hand experience, rookie engineers don’t know beans about proper, efficient lateral design. It is not taught in college, it must be learned under the tutelage of a well-seasoned professional. Regardless, there are many rookie engineers struggling to carve out their niche, so they learn — at your expense. While their designs can be unpredictable and erratic, there is one common thread: rookie engineers are scared to death of liability. So, they overdesign. Where no holdowns are needed, they put five. Where anchor bolts should be spaced at 48-inches, they space them at 24. But even worse, a rookie engineer very frequently pays no attention to the most important thing of all in lateral design: load path. So he may have a heck-for-stout shear wall connected to a roof diaphragm using only three toenails. Very dangerous.
- An experienced engineer is hired, but the engineer is overly conservative. In this scenario, the engineer knows what to do and how to do it, but he is scared-white the big one will come someday, selectively seek out his buildings and tear them apart. He ignores the fact that things built to code are 150% stronger than they need to be (this equates to the code-standard Factor of Safety of 2.5). So, whenever a designed item is on the fence, i.e., it could go either stronger or weaker, he always chooses stronger. Rather than take into account all the factors helping to resist lateral loads, such as interior walls, he ignores them. Rather than counting on the weight of the building to hold itself down, he ignores it and puts in 20 additional holdowns. And so on. Very expensive.
- An experienced engineer is hired, but he is lazy. This engineer has been at it too long. He doesn’t really like pushing the buttons on his calculator any more, and writing equations makes his wrist tired. So, he eyeballs things, more or less, and throws in lots of holdowns and shear walls — just to be safe. Expensive, and potentially dangerous.
How Much Is the Cost? Seasoned builders know you’ll spend more on over-engineered construction than the fee for an intelligent design up-front. For example, certain holdowns cost upwards of $50 each — just for materials. Add labor and they’re $100. If there are 20 more than need be, that’s $2,000 just for unnecessary holdowns. Add in a bunch of other over-engineered items and this cost can easily double. The engineering fee for lateral design of a standard 2,000 square foot home should be in the $1,000 dollar range. Go figure. The problem becomes, then, how to find the right engineer? My best recommendation is word of mouth. Engineers are typically good at selling themselves. You’ll have a hard time knowing the good from the not-so-good unless you or someone you trust has actually seen a few of their designs. If word of mouth doesn’t work for you, ask your would-be engineer this question: “How many similar lateral designs have you personally done in the last five years? ”If the answer is evasive, vague or “less than 25,” keep looking. Will a good, experienced engineer have a higher fee than a rookie? Probably, but not too much higher, say no more than 25%. Regardless, it will be money well spent because the good engineer’s design should: - Go through plan check faster
- Have fewer errors — callbacks
- Be more construction-friendly; i.e. more in line with the local way of doing things
- Be more efficient — i.e. not over-engineered
- Be a safer, better design for the owner
In the world of engineering, the old adage rings true: what you don’t know can cost you. Your best defense is to educate yourself. Learn all you can about how loads act on buildings and how buildings resist those loads. Understand what a holdown really does. Learn load path. Read my book, "Basic Structural Concepts for the Non-Engineer." Because once you understand, you’ll be able to spot problems and inefficiencies before they cost you money, or worse, someone’s life. Tim K. Garrison P.E. of ConstructionCalc.com has authored books and short courses and lectures on topics relevant to builders. Got a technical or management issue? E-mail buildersengineer@constructioncalc.com. Tim reads every one. This column cannot be reprinted without permission from the author. The views expressed in this article represent the personal views, statements and opinions of the author and do not necessarily represent the views, statements, opinions or policies of the National Association of Home Builders. NAHB does not necessarily endorse any of the views expressed by the author and NAHB is not responsible for any direct or indirect consequences arising out of the views expressed in this article. |
When the following column was originally published over two years ago, it touched off a firestorm of responses, both positive and negative. It has run in architects’, engineers’ and builders' magazines. Amazingly, I still get feedback from this timeless gem. Here it is again, in case you missed it. 