This article, regarding hardwood floor installation, by South Texas Flooring Company, 713-660-9189, discusses the differences in nail-down & glue-down installations, specifically in the Houston area.
In the past, when all homes in the Houston vicinity were built on pier & beam foundations (generally before WW II), the wood floors were nailed over a pine subfloor to the home’s wood-frame foundation structure. The subfloor, typically rough-cut 2 x 6 boards, were nailed or screwed to the floor joists (no plywood around in those days), and then the actual floorboards were nailed to these 2 x 6’s. This process was structurally sound and built to last, and many older homes in the Rice University area, the Heights, and other older parts of Houston still have the original flooring installed using this method.
But after WW II, most Houston homes were built on a concrete slab. There was no adhesive available that was strong enough to hold these solid hardwood floor boards to concrete, and so- called “engineered” wood flooring had not yet been developed, so a method had to be devised to attach the solid hardwood flooring to the slab. (Note that solid hardwoods can still be nailed directly to upper level plywood subfloors.) The process that was developed to install solid hardwoods over concrete is still in use today, at least in homes with concrete slabs and solid wood flooring. This method involves pouring hot, black tar directly onto the concrete slab, at a thickness of about 1/4″, and then laying “screeds” (1×4 or 2×4 pine sleepers, typically 2 feet long) into the hot tar, about 6″ or so from each other. The tar hardens quickly, and will hold these screeds in place for decades, barring moisture or water intrusion. The hardwood flooring is then nailed directly onto these screeds, and then sanded and finished with stain and urethane.
With the 1970’s came two developments – 1) “engineered” wood flooring, and 2) adhesive strong enough to hold this engineered flooring to concrete. (Adhesives, even today, will not adequately hold solid wood flooring to concrete.) The engineered wood (discussed in detail on another blog on this website), consists of several layers of plywood-type material, with the top layer being the hardwood, usually oak. In most cases, this top layer is factory finished, so no sanding and finishing is necessary on the job site.
Today, both nail-down solid hardwoods and glue down engineered wood flooring is installed in Houston homes, depending on the preference of the builder and/or homeowner.
