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da_man 09-10-2013 06:51 PM

notiing some cupping and air bubbles on my hardwood floor
I installed these floors myself about 8 months ago. I used 3/4 inch red oak, red rosin paper, bona floorpoly from homedepot. The room is above the garage. I am noticing cupping, it doesn't look bad, but you can really feel it if you drag your feet across the floor. I am also noticing air bubbles that were not there when I put the polyurethane on.

I ran some wire in my garage ceiling a while back and saw that the insulation between 3x16 I joists fell down in some spots because there were no insulation support wires used. Not sure if this this is a deciding factor.

I also installed floors in another room that is not above the garage about 2 months ago and so far it seems fine.

Just wondering if the insulation in my garage can cause this issue or if there could be something else. I am not sure if it is a moisture problem as my garage gets humid in the summer or if it is an expansion and contraction problem.

joecaption 09-10-2013 07:10 PM

Both signs of moisture.
Bet there was no vapor barrier installed before the sheetrock went up and or no plastic laid under the slab.
Did you do a moisture test on the subfloor before installed it?

JazMan 09-10-2013 07:13 PM

You guessed it, it's too much moisture from below. You should fix the insulation issue and maybe improve the "R" factor while you're at it.

How come you used red rosin paper instead of tarpaper? Tarpaper is a moisture retarder, red rosin doesn't do much at all.


JetSwet 09-14-2013 07:28 PM

I doubt its from the insulation falling. The question to ask is what size nails were used. And what does the floor manufacture say about type of poly used?... Most types of hardwood won't except roofing felt as a barrier. Rosin paper is fine has been used for many many years.

JazMan 09-14-2013 11:24 PM

From the NWFA (National Wood Flooring Association)

1. A vapor retarder has some extra benefits in that it eliminates wood-on-wood contact, wood strips slide more easily when positioned, minimizes the impact of seasonal humidity change and may reduce dust and noise levels.

2. However, by today’s standards, asphalt saturated kraft or felt paper may not be an effective vapor retarder in all applications. The 2006 International Residential Code requires a vapor retarder on the warm-in-winter side of exterior floors (a floor over a vented crawl space, for example), with a vapor permeance of 1 perm or less in Zones 5 and higher.

3. Over a wood subfloor, do not use an impermeable vapor retarder material with a perm rating of .7 or less, such as 6 mil polyethylene film or other polymer materials, as it may trap moisture on or in the wood subfloor.

4. Do not use common red rosin or building paper which is not asphalt saturated. They are not vapor retarders as their perm rating is far greater than 50.

I'm no expert on solid hardwood flooring, but I like to follow directions.


JetSwet 09-15-2013 05:14 PM

There is really no need for asphalt paper when you have a conditioned area under your floor like garage that is sheet rocked with insulation unless there is no insulation and defiantly not use it if there is plastic on studs. If your floor is above a unfinished basement or dirt floor by all means use asphalt paper.

Gary in WA 09-15-2013 11:56 PM

As long as you air seal the vehicle door, don't ever park a wet car in there, add a heat supply/return and vapor barrier poly under the vapor permeable concrete slab....


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