Why Does Wood Warp?

According to the NAHB analysis of 2021 Census Bureau data, for 2021 completions, 92% of new homes were wood-framed. This was an 8% gain over the 2020 total. 7% were concrete-framed homes, and less than half a percent was steel-framed.

Even though supply-chain issues have resulted in higher lumber prices, wood framing is still the most common construction method for single family homes.

One common problem that homebuilders run into when using wood is that it has a tendency to warp after it has been utilized on the jobsite. “When a long-sized lumber, such as a beam or a bearer, is produced from the felled log by using a band saw, it often exhibits bow, crook, twist and/or other warps.” (Yamamoto, 126). Recent research has even shown that almost every piece of structural lumber has measurable warp, (Wagner, 59). Why does wood warp?

Consider how this can impact both the customer’s experience and the homebuilding industry as a whole. “Problems detected after a product goes into service will be costly to repair and will damage the reputation of the supplier and the wood industry in general, ” (Garrahan, 30). “When warp develops in-service, costly claims to fix bowed drywall, cracked plaster, nail pops, and warped siding can result,” (Shmulsky, 38).

After wood is utilized in the homebuilding process, it continues to dry out. As water exits the cells of the wood, shrinkage occurs. This results in the wood no longer being as flat as it appeared at the lumber yard. This is the “warp” that we see so often, which then causes issues such as screw pops and floor squeaks. The moisture content of the wood might also increase, resulting in a swelling effect, which would also cause warping.

“Warp in lumber (bow, crook, and twist) is often caused by different longitudinal, radial, and tangential shrinkage when water is removed from the wood cell walls. Warp normally occurs during seasoning when lumber is dried below the fiber saturation point, but may begin at moisture contents (MCs) in excess of 40 percent. Warping may be aggravated by irregular or distorted grain and by the presence of abnormal wood types,” (Beard, 51).

There are multiple ways that wood might warp, depending on factors such as the grain direction, the proximity to the bark, wood species, exposure to the elements, etc. Below I will lay out the different types of warp. First, consider the below graphic showing the general break down statistically of the different warp types for Acacia Mangium wood (as an example) based on cut types:

As mentioned previously, wood warp results in problems for homebuilders. Consider the use of nails on joists in subflooring. When those joists inevitably begin to warp, the resulting up-and-down movement of the nails causes that “squeak” that we hear while walking across the floor.

“There are few problems that will destroy a customer’s confidence in their newly installed floor faster than an annoying squeak. When they hear that dreaded sound rising up from the floor, they know something is not right and they bein to point fingers. Often the blame falls on the flooring retailer or whoever sold them the floor,” (Thompson, 1).

One option you have in preventing this from happening is the use of TYTAN Professional Subfloor Adhesive, which is designed to stop the annoying floor squeaks. It is an adhesive that bonds the subflooring to the joist, thus preventing that up-and-down motion that results in the squeaking sound. Over the 24 hour period after application, it expands to fill gaps, cracks, and inconsistencies in the lumber.

If you have questions regarding your specific project, reach out to your local dedicated TYTAN Professional Representative. You can also give us a call at 817-381-4427.

“The Share of Wood-Framed Homes Increased in 2021” – NAHB Eye On Housing: National Association of Home Builders Discusses Economics and Housing Policy

Beard, J.S, F.G Wagner, F.W Taylor, and R.D Seale. “The Influence of Growth Characteristics on Warp in Two Structural Grades of Southern Pine Lumber.” Forest products journal 43, no. 6 (1993): 51–56.

C Tenorio, R Moya, and HJ Quesada-Pineda. “KILN DRYING OF ACACIA MANGIUM WOOD: COLOUR, SHRINKAGE, WARP, SPLIT AND CHECK IN DRIED LUMBER.” Journal of tropical forest science 24, no. 1 (2012): 125–139

Peter Garrahan. “Keeping the Customer Happy.” Canadian forest industries (2011): 30–.

Shmulsky, R, R.W Erickson, P.H Steele, and D Buckner. “Warp Reduction of SYP Lumber by Restrained Drying.” Forest products journal 55, no. 9 (2005): 37–41.

Thompson, Ray, Jr. “Keep it quiet: understanding why floors squeak.” National Floor Trends, October 2007, 50+.

Vignesh, V., A.N. Balaji, B. Raja Mohamed Rabi, N. Rajini, N. Ayrilmis, M.K.V. Karthikeyan, Faruq Mohammad, Sikiru Oluwarotimi Ismail, and Hamad A. Al-Lohedan. “Cellulosic Fiber Based Hybrid Composites: A Comparative Investigation into Their Structurally Influencing Mechanical Properties.” Construction & building materials 271 (2021): 121587–.

Wagner, F.G, and F.W Taylor. “Impact of Log Sweep on Warp in Southern Pine Structural Lumber.” Forest products journal 45, no. 2 (1995): 59–62.