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Reduce Wood Warping

DIY Questions and Answer January 11, 2008 admin


Q: I recently finished adding a deck to my house. I’ve noticed part of my handrail is warping. I used treated wood, 2-by-4 and spindles for the handrail. Is there anything I can do to prevent or limit the warping?

A: For this question, EHT turned to treated-wood expert Huck DeVenzio of Wolmanized Wood. Here’s what he had to say:
“Wood has many outstanding properties, but it is a natural, porous material with individual characteristics, and it can warp. When wood gets wet, it swells. When wood dries out after being sawn from the tree, after being pressure-treated and after rain showers, it shrinks. Uneven drying creates stresses in wood, which results in warping (e.g., bowing, cupping or twisting) or cracking. The degree of warping depends on the species of wood, its grain pattern, uniformity of drying and construction techniques, among other factors.
“Although it is possible to position bowed deck lumber so that its weight flattens it, or to use screws to fasten securely an otherwise warped piece, there is not much a user can do to truly un-warp a warped piece of wood. It is best to take steps early to minimize the likelihood of warping. For example, you can purchase treated wood that is Kiln-Dried After Treatment (KDAT). This step removes moisture evenly under controlled conditions, so you don’t have sunshine drying the top of a deck while the underside faces moist earth. Or, you can get wood with built-in water repellent, which helps to slow down the release and absorption of water. In either case, it is always advisable to apply a water-repellent coating every year or so to reduce further water absorption in surfaces where good appearance is desirable.
“In building a project, you can avoid long, unsupported spans, and you can make sure to use enough fasteners to hold wood firmly in place. Screws have better holding power than normal nails. As a last resort, it may help to flip some cupped deck boards and encase a twisted column with fascia boards. Badly warped pieces may have to be replaced.
“Some warping is always a possibility, but this should not discourage the use of a convenient, economical, attractive, long-lasting and renewable building material like pressure-treated wood. For more information on preserved lumber and other maintenance tips, visit www.wolmanizedwood.com.”