I’ve been tasked with taking some old flooring, like 1860’s old, and making it into viable flooring for a new application. Planeing it down, new tongue and groove, etc. One of the things asked was to put grooves on the underside. What is this for, and is it necessary on wood that old? I’d assume (always dangerous) that the lumber is pretty stable at this point.
It is primarily done to prevent squeaking. If the planks have no relief, any cupping (warping parallel to the length) the plank will only touch the subfloor along one line and will make noise when you step on it. with the relief it will tend to contact along multiple lines and not squeak even if there is a modest cup. Of course, wood can still bow or twist and the grooves won’t do much about that. Well seasoned wood won’t warp from loss of volatiles but it it can still develop warpage from residual stress, moisture or heating, et cetera.
Stranger