Q: We are replacing carpeted stairs with oak stair treads. We ripped up the carpet and pulled up the existing pine boards. My husband says we have to put plywood under the 1 ½ inch oak treads we purchased. I say we just have to replace the risers and glue and nail the treads to the stringers.
The treads are 41″ across, and there are three stringers, left, middle, and right.
A: If your slab treads are 1 1/2″ thick, I know of no reason plywood is needed. I’ve worked in hundreds of homes and never seen that, though the treads were 1 1/8 thick. Sounds like the outside stringers are notched, rather than having a slot cut in them, wherein the treads are slid in and held by wedges. Yours will just sit on the cut out of the stinger. I would apply a bit of adhesive and perhaps counter bore 2 screw holes on each end, to be plugged with oak dowel.