Replace over 100 cracked boards or replace whole floor?

Q: In our new home (we have had it for 3 months) the maple floorboards are cracking. Our builder wants to lift and replace only the cracked boards. However, at this stage there are over 100 boards that need replacing, and more are cracking as time goes on. We have installed a dehumidifier in the home as the builder thinks it’s due to too much humidity because we had cupping as well.

My question is, once so many boards are lifted and replaced by gluing in, will they lift and become uneven over time? Will my floors look level in say 4 or 5 years? I have heard that the glued floorboards will eventually not be level and I think the builder should be replacing the entire floor.

A: I will make an assumption that your maple floor is pre-finished and has bevelled edges. You may be surprised to know the reason they have the bevels (eased edges) is because these floors are NOT perfectly flat. The edges help to hide that. If he uses a polyurethane adhesive I would not expect the boards to move or come loose.

I would certainly be concerned about the cupping of the floor. It is definitely connected with excess moisture coming from below the floor. I doubt this is caused just by excess humidity. Has anyone placed a hygrometer on the floor to see what the RH is in the home? What about a moisture meter to take some readings of the wood itself? This is something that should be done before the floor is ever installed. Was the sub floor and the maple checked with a meter before installation began? It is a new house. At some point it was wide open with no roof, no windows, no heat and exposed to the elements. The plywood at some point had to be wet. Was it within 4% moisture content of the moisture in the maple when first installed?

The horse is out of the barn now. I don’t know the square footage of the entire floor area. Over 100 boards needing to be replaced seems like a lot. Sometimes it makes more sense to just start over, but apparently the builder doesn’t feel that is the case.

How are they going to deal with the cupping? The source of the moisture will need to be addressed first. If the basement is open, they may want to put a meter on the plywood to check it’s moisture content. If the floor now shrinks as the heating system comes on you may then be left with a lot of gaps.