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Home >> Articles >> Things learned from last summer’s tornado, hail storm and drought
 From The Best Times - January 2004By Don Carter, Structural Engineer 1. The tornado came on May 4, and within 24 hours FEMA was requiring structural engineering evaluations for damaged houses. My partners and I were there early and saw the damage well before cleanup began. We observed block after block where some houses were leveled. Then there would be one or two standing, then a couple missing and so on. We wondered why some survived and others failed. Often the answer was as simple as nuts and bolts. All the houses had anchor bolts to join the frame and foundation, but oddly only some had their nuts and washers on them. It’s kind of like putting your spare tire on without the lug nuts and expecting it to work. When the houses without washers and nuts got hit with high wind, they lifted and as soon as air got under them they were history. I now focus on this during inspections and see homes, in every price range, without nuts on their anchor bolts. This is a gray area for Codes Inspectors inasmuch as they check to see that the bolts are there, but do not typically confirm that nuts ever get installed. Check your home - it could make a big difference. 2. The hail storm came on June 23, and cut a path of damage across South Johnson County. Wood roofs took a beating with nearly 100 percent replacement required in some neighborhoods. My roof was only three years old and looked pretty good at first glance. However, once tested, it proved too damaged to save and we were faced with decisions about replacement. When our subdivision was platted, cedar shingles were the covenant-required standard, no exceptions. But the old rules got overturned and we had a chance to re-roof with cedar, composition or steel. As part of their presentation, roofers asked if our house had an abnormal number of silverfish or spiders—which we do. Apparently silverfish are drawn to cedar roofs and then the spiders that feed on them follow. When the day came to strip off our old roof, I went into the attic, which was then fully lit by daylight, and was astonished at the number of silverfish scurrying among the remaining cedar shingles. We replaced with composition. 3. Last summer was hot and dry, the second year in a row with below normal rain fall. Officially declared a drought on July 22, lawns and trees began to show distress shortly thereafter. As clay soils lost grass cover and trees began to compete for ground water, houses started revealing the ugly signs of misalignment. I estimate that less than 5 percent of the drought damaged houses we assessed had sprinkler systems, suggesting that a lawn irrigation system is cheap insurance against drought. The logic is simple. A timer-controlled sprinkler comes on in June and wets the surface every 2nd or 3rd day. Grass stays green keeping the topsoil moist and bulky. This in turn protects the soil beneath from drying and shrinking. For about one-eighth the cost of fixing a misaligned house, you can own and operate a yard sprinkler. And when you get ready to sell the house much of that investment comes back in the form of higher appraisal. Don Carter is a licensed structural engineer and managing general partner of Foundation Engineering Specialists LLC, a company specializing in residential design and assessments.  |
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