Two weeks ago, I have completed half of a 12X22 room (I’ve done 6′) with prefinished maple. I noticed that the new floor slants down toward the center almost a 1/4″. The subfloor/underlayments was relatively flat or actually slanted the opposite direction,down toward the edge of the room where I started. The slight quirk is that it is installed over oak parquet glued to a plywood subfloor. I’m using a Porta Nailer tool, nailing about every 8 inches, and used a moisture barrier on top of the parquet. Everything else is going well, the joints are tight and straight, and the floor looks good. Any idea of what is going on or of what I can do before I finish the other half of the room? Is this just the wood settling in? The joist run along the 12′ direction, and the flooring is along the 22′ direction.
Stop what you are doing. You should NEVER, NEVER NEVER install a hardwood strip floor over any type of hardwood, and the parquet is just about the worst choice in nailing surfaces. You must start all over or you will have a creaky squeaky floor in just a few years. The parquet needs to be removed and the plywood checked for it thickness. Then and only then can we talk about what is happening. I hope you are using flooring nails and not staples. Staples have been known to crack the tongues off and cause a slanting of the wood.
As always your Most humble servant, Joseph, the Wood Floor Doctor.