Thanks in advance for your advice.

I am currently building a new home and have a concern about our wood floors going in. We selected Cumaru (Southern Chestnut) and the builder has the contractor beginning to install the flooring on the first level. The flooring is going in before any cabinetry. We are located in the northern midwest where the weather has been in the 80's - 90's F with about 60% humidity. The house has been closed up for a while (windows, doors, roof, etc.) and so there has been no moisture coming into the house other than the outside air. The flooring was delivered last week and my wife met one of the installers in the house Friday who was setting up fans. He told my wife that there was too much moisture in the plywood underflooring to start the installation, and apparently was using fans to dry it out. Today they started installing the flooring at the top of our front stairs, and I assume they will start downstairs tomorrow.

Does this seem like a setup for shrinkage later on? Installing the flooring in 60% humidity (outdoor weather conditions), so that later on when the AC is hooked up and the temperature and humidity is brought down to 70F and 30-40%, the boards will lose some of their moisture and shrink. I brought this up to our builder in an e-mail (was gone all weekend) and haven't heard back yet. The use of the fans is puzzling to me since they would be blowing 60% humidity air onto plywood that has been in equilibrium with 60% humidity air - hence nothing to dry out. Meanwhile the flooring is absorbing moisture from the house at 60% humidity.

I am concerned that we will have considerable shrinkage, and repair will be difficult since all the cabinets are installed on top of the flooring. This is a high end home and we want to make sure we don't have to repair it later, especially since we thought of it now. We were told not to use Cumaru because the builder has had problems with shrinkage in several of thier past projects. The builder generally prefers quartersawn red oak, but the stability of cumaru is better than red oak according to the test data. Does anyone else have concerns with this scenario???

Thanks again

The AC needs to be on for 1 to 2 weeks BEFORE any installation of flooring begins. In most of the instructions it states how long AC or heater should be operable prior to install. If this is not followed and when the floor fails, the mill will not stand behind it due to installer error.

Regardless of which type of wood flooring one is installing, the building needs to be at normal living conditions. If that is 60% RH, then you are fine. But typically, 45 to 50% RH is the norm. The subfloor and wood flooring need to be within 4% MC of each other for strip flooring and preferably, 2% MC. I suggest running the AC to bring the humidity and temperatures into the normal range before proceeding with the installation.
https://www.nofma.org/Portals/0/Publica ... rmance.pdf
https://www.nofma.org/Portals/0/Publica ... isture.pdf
https://www.nofma.org/Portals/0/Publica ... 005_04.pdf

Cumaru is prone to shrinking, the rh will have to always be kept at 60% if you want that floor to be tight if installed that way. Ask what the flooring and subfloor are reading and write it down it will be good to have this winter when you floor shrinks down. I have beacome a big fan of humidistats that many are putting on the hvac. It will keep the temp and r/h at your chosen levels making your floor much more stable while its in service.

Typical fast paced builder!!! Throw standards out the window, in order to line his pockets faster!!


Acclimation of the wood can't even start until the HVAC unit has been operational and running for at least 2 weeks minimum.


Yes, your going to have big gaps, as soon as the HVAC unit starts running and pulling the moisture from the air, via the evaporator core. Then come winter time and the drying effect heat adds, your in for some huge gapping!!

This is going to come back installation related, as the installer or installers employer, accepted the conditions the wood id installed in, and that at this point is out of industry standards, concerning job site conditions, and acclimation requirements, not recommendations.