From time to time, there are always some customers complaining about the width difference for the same solid wood floor product that the difference can be up to 1-2 mm. This is not easy to justify since NWFA standard only allows +- 0.005″ for 3-1/4″ or less stripe or +- 0.008″ for planks wider than 3-1/4″. But is the NWFA standard realistic?
Today I came across an article with a good answer. Basically this article points out a very good fact that each plank, even in the same carton, may come with different moisture content (MC) level. According to NWFA standard, a 6-10% MC level variation is allowed for the fresh manufatured product. So because the 4% MC difference is allowed, we can readly get the width difference allowance using the following formula:
% moisture change x width x C ( C is the dimensional change coefficient )
From the above formula, we can get the width difference between 3-1/4″ wide plank can be 1.2mm and 1.8mm for 5″ plank, which is very normal in real life.
So we may want to let the customer know this before they purchase the wood floor that no surprise afterwards.
Reference is here: https://www.woodfloorbusiness.com/wood-flooring/prefinished/article/15125426/it-varies-we-cant-expect-solid-prefinished-wood-floor-widths-to-be-perfect#:~:text=A%20newly%20educated%20expert%20may%20quote%20the%20new%20NWFA%20standard%3A&text=for%20flooring%20with%20an%20actual,is%20%2B%20or%20%2D%200.005%E2%80%9D.&text=for%20flooring%20greater%20than%203,is%20%2B%20or%20%2D%200.008%E2%80%9D.