My wife and I are under pressure to get into our new home as our possession date on our current home is coming up fast. Our builder says the holdup is the hardwood installation cannot be done as our subfloors (3/4 inch plywood) test 20% moisture. The wood to be installed is 3 1/4 inch by 3/4 inch solid Merbau.

Today I have set up six dehumidifiers in the house (four upstairs and two in our basement, which has a suspended wood structural floor of 5/8 inch plywood) plus four fans and have the A/C down to 62 degrees. Is there anything else I can do to help dry the place out quickly?

Right now the dehumidifier is reading 45% RH in the house. Our humidity jumps around here as the weather does, but luckily we have several good hot days (at least for Winnipeg, Canada) of 85 degrees or so coming up. To me it makes sense to open the house up completely when the RH outside is lower than the RH inside, then close it up when the converse is true.

Any advice is greatly appreciated!

How did the plywood get so wet? At any rate, your builder is looking out for your interests as he is correct that the plywood @ 20% is WAY to damp to lay a floor over. However, it should dry out quickly with all that is going on. You may want to test the subfloors with a different moisture meter as it is possible that the one the builder is using may not be calibrated correctly. Is the flooring inside the house now? My concern would be that you are artificially lowering the normal RH and therefore, lowering the MC of the flooring as well. Ideally, subfloors should measure about 8 to 10% MC with the wood flooring within 2% of that measurement. RH should be maintained year round between 45 to 50%. In Manitoba, things maybe a little dryer but if it is lower than 35% RH, it is too dry and humidifiers are needed. Good luck.

Wow, thanks for the prompt and helpful response!



It was snowed on a few times and even though I shoveled the entire 1850 sqft area twice, there would have been some residual moisture without a doubt. It also rained on it a few times before the roof got put on this spring. The builder and trades did not seem at all concerned about keeping it dry during these times.



Yes, he's said not to do it until 10 or 12%. He said the flooring company would install it higher but only if we signed a waiver--sounds like a bad idea to me.



The company laying the flooring is the one doing the testing; I will ask them to double-check. They will be testing again in a few days.



The flooring is not in the house yet. I think they will wait until the RH in the house is down (reading 44% when I was there earlier) before moving the flooring in.



The new place has an HRV unit with a humidistat with various settings for summer vs. different winter temperatures. We should be able to control our humidity effectively.



Just another question in case you or somebody else can answer: the last few days the RH outside has been high, so we have the A/C cranked, the furnace fan on constantly, and the HRV working along with the aforementioned dehumidifiers and fans. So the RH inside the house today was in the forties, with higher RH outside. And we have taken great pains to keep the house "closed up" since we discovered the subfloor to be that moist.

So is it then a good idea to "open up" the house if it turns warm and dry outside as expected? If the dehumidifiers get the air inside the house into the thirties, but if RH outside the house is in the teens or twenties, doesn't it make sense to get the now more moist air inside the house changed with now drier outside air? Is there any potential downside to this?

Any other tips for drying out our house quickly would be greatly appreciated. And thanks once again Gary for your help.

In new construction, a lot of green, damp building material is used. The paint, the drywall joint compound, the texturing compound, the tile work and thinset, concrete, and the lumber. All of it is wet and damp when used. It takes quite awhile for those things to dry out, not to mention the snow and rain that doussed your home. It seems to me you are doing all you can. A couple of industrial fans working overtime with the windows open when things warm up will get the humidity out of the house asap. Rely on the meter readings, that will tell the true picture.

Will do, Gary. Thanks once again.

I would say turn the a/c off if you have dehumidifiers running for two reasons. The low temperatures will hinder evaporation and reduce the efficiency of the dehumidifiers. Optimally the temp should be around 80 degrees, dehumidifiers work best between 70 and 90 degrees, try and hit the top end to help evaporation. Maybe try some infrared heaters directly on the wettest areas.

Way to bump an old post that is long gone....