Underlayment for hardwood flooring…
Diomedes
| Posted in Construction Techniques on
I am installing Hardwood flooring overtop of the existing subfloor (looks like its 2-3/4 wide fir planks that are 3/4 inch thick). I have gutted the basement and it seems to be quite damp down there, I am just curious if I should place roofers felt down on the subfloor before I start installing the new hard wood (3/4 inch maple). I have read that it will act as a vapour barrier. I am just curious if this is an acceptable practice or if there is a better product out there. This will be my first time installing hardwood flooring and I would appreciate any helpfull hints.
Replies
I'n not clear on what you have. Sounds like the current existing is fir T&G flooring directly on the joists with no subfloor under it, biut it will become the subfloor when you add this ply - right?
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The "hardwood flooring association" standards calls for felt paper under a nail down hardwood floor.
It's amin purpose is for a slip sheet to reduce squeaks.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Absolutely - that's what the manf. reccomend anyways.
JT
The dampness in the basement must be addressed befor flooring is installed.
We won't put hardwood on anything but ply due to the number of squeeks.
Beer was created so carpenters wouldn't rule the world.
The reason I asked him how many layers he has now for clarification is that if he has a true subfloor and then the fir flooring he describes is that there may already be a layer of tarpaper between the two.If that is the case, adding another ply of tarpaper ould concieveably trap moisture in the middle and make tht fir get spongy after time, leaving him with a very unsatisfactory floor. If that is the case, he should find a place to test drill to find out oif there is tarpaper layered in. But I am aware that in some places, like the Gulf Coast and southern California, it was once common to lay fir T&G directly on floor joists over crawls, so tht may be what he has. In this case, the preferred method would be to install ply underlayment over the fir with glue and screwss, then the felt, then the new floor. This would yield a better floor and a better nailing surface, and the glue would limit sqeaks
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For damp(er) locations there is an underlayment that is two layers of kraft-like paper with an asphaltic layer in between.
Jeff
We call it "triple 30" around here. I lay quite a bit of flooring and it's all I use. Lays flat and smooth. Roll covers 500 sq. ft.
You might consider thoroughly walking the existing plank sub-floor before you continue, to determine if it squeaks. If it does, and you don't stop any squeaks before you continue, it will likely continue to do so after you have completed your job, driving you and your client crazy!
I would say that a good felt underlay paper would be sufficient. If moisture is great enough for you to ask the question in the first place I would be inclined to test the moisture % in the basement. The flooring manufacturer will have an allowable moisture level for their floors. Also I would look into solving the moisture problem before it becomes a structural and/or health issue.
Dave
Not sure what you mean by measuring the moisture percentage in the basement?????Taking a reading in an area would usually mean checking the RH - relative humidity - which is a read on the amount of moisture in the air relative to how much it is possible to hold.This means exactly nothing when dealing with the wood. It is typical to stabilize flooring to the same moisture level as the wood in the subfloor and rest of house before installing it, but this reading is based on percentageby weight I believe of moisture in the wood - in other words relative to the total weight of the wood.Thje only way the two are related is that if the humidity in the air is constantly high, the wood will eventually absorb more into itself. but this new flooring is not being installed in the basement. It is going above, so isolating it from the air there with a membrane such as the felt will limit moisture that the flooring can absorb from below.The other steps he should take is to seal the new flooring on the back side before laying it and to ventilate the basement or add a dehumidifier.I understood his primary Q to be one more of whether trapping that moisture below was apt to cause rot or mold, which of course is true. But he has so far failed to return and read any of the replies or answer anyones return questions.. So without much information, all we can do is to speculate now.
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Can you answer some of these questions posed to you so you can have a more acurate answer?
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