Installing Strip Flooring and Avoiding Future Squeaks and Pops

The subfloor is the first thing to take a close look at, even if you are you installing a new strip floor in a modern house with a plywood or OSB subfloor. It should be of no great surprise that the modern building code requirements are there as a minimum safety standard. Subfloor squeaks are not considered to be a safety factor. The writers of most cities’ building codes just don’t want you or a piece of heavy furniture falling through between the joists, that’s all.

All the subfloor specs I will mention here are assuming your floor joist are 16″ on centers. If they are 20″ – 24″ apart you must add another layer of plywood to give enough stiffness to the hardwood strip floor. This is best done by using underlay plywood of at least the 1/2″ thickness. I’d like to see a minimum thickness of 3/4″ plywood between 16″ joists, but a full one-inch of plywood between 24″ joists. This extra thickness is needed in the long spans to prevent the hardwood flooring from deflecting too much and causing squeaks (a loosening of the nails). And it would behoove you to squiggle some urethane construction adhesive between these layers of plywood subfloor to prevent future floor squeaks.

Never, never, never nail a new hardwood strip floor to a old hardwood strip floor. The flooring nails will crack the old hardwood and you will have a double squeaky floor. Remove it and use the softwood subfloor, it makes a much better nailing surface

I have seen nail withdrawal studies of strip floors nailed to various subfloors; pine boards, plywood and OSB. This investigation was done by Virginia Polytech Institute at Blacksburg, Va. The study makes the conclusion that the best sub floors are the thickest and surprisingly the solid wood pine 3/4″ held the nails the best. Next down the list was the 3/4″ plywood and 3/4″ OSB was about the same.

But OSB gets into trouble when it gets wet during the early stages of construction. An unsheathed roof or walls left un-tarped for a rainy weekend, leaves OSB swollen and permanently damaged. It is rarely replaced, just re-nailed and sanded smooth. But the damage inside these panels is set. During the manufacturing process some of the wood chips are folded, and now they have been released during the swelling. Now as the frustrated home owner walks on the dried out floor a popping sound occurs as these double stressed chips finally break. The hardwood floor installer is sometimes blamed for this, as it looks like the finished hardwood floor is popping. But the problem, we know now is deeper.