Is roofing felt under plank flooring always needed?

[tbasc]

See the NOFMA web site for installation tips. NOFMA is a wood flooring manufactureres association. They should know what they are talking about. TB

[Colbyt]

I think it is also used to control squeaks. That said I would use 30# felt and not the cheaper 15#.

Colbyt

[Harry K]

I don't get it. What is with the 'do I need felt' questions this year. The cost of the felt is such a miniscule amount compared to the other material why the hell not use it when it is recommended?

Harry K

[Dick Shenary]

Does roofing felt serve an additional function when laid under a hardwood floor besides being a moisture barrier? I'm installing 3/4" plank in an upstairs room over a plywood sub-floor. Do I need felt underneath?

[Dick Shenary]

I can't speak for the other "'do I need felt' questions this year" but in my case the cost did not motivate my question. My question was about the need for a moisture barrier in a situation where moisture is not an issue. I asked if roofing felt served an additional function besides that of a moisture barrier.

I don't get it. What is with the "I don't know the answer but I'll give the guy a hard time for asking" posts this year.

Thanks a bunch, Harry.

[Harry K]

My comment was not addressed to you specifically. It does still apply tho.

Harry K

[RicodJour]

Let me start by saying that I personally use felt on every job. It takes only a few minutes to put down, costs a few bucks and you have a nice clean floor to work off of.

When I pull up old strip floors there's always paper between the finish flooring and the diagonally-sheathed 1xwhatever subfloor. The paper, any paper, acts as a barrier in such floors. It keeps dust and dirt from percolating down through the subfloor. Usually the paper I find is red rosin paper and not building felt. Possibly the use of felt is just a holdover from the old 1x subfloor days.

I don't think felt's moisture barrier qualities are its main function in a floor that's over conditioned space. Over a crawl space it's cheap insurance.

The subfloor and strip flooring do expand and contract at different rates, so there is slidng of one on the other. Having paper facilitates that sliding, but to what degree I can't tell you - never seen a study on it.

R

[Heathcliff]

You are only one roof leak, left-open window or tipped-over goldfish bowl from needing a moisture barrier.

[Wayne Whitney]

"My question was about the need for a moisture barrier" [underneath hardwood floor] "in a situation where moisture is not an issue. I asked if roofing felt served an additional function besides that of a moisture barrier."

I have heard that felt between a hardwood floor and the subfloor is also useful to separate the possibly different directions of expansion and contraction of the two materials. Less friction between hardwood and felt than between hardwood and subfloor? I'm not so clear on the details.

Cheers, Wayne

[RicodJour]

situation

Actually, the felt would tend to hold water against the bottom fo the strip flooring and keep it wet instead of letting it soak into the subfloor and escaping that way. Pretty much exactly the opposite of what you'd want to do.

R

[Art]

If it is prefinished flooring you need to follow manufacturers instructions.

[Dick Shenary]

Thanks Wayne. That's what I was thinking, too. Essentially a "lubricant".

[Dick Shenary]

Thank you for the info. I appreciate your experience. From what I am reading here and elsewhere I'm getting the impression that it's use as a moisture barrier is secondary to it's lubricant property.

[Dick Shenary]

LOL Good point, and thanks.

[rosie read n' post]

speaking of wood floors.....................what do you guys like best? we are going with prefinished, but question which is better...............glued down or floating?

[Edwin Pawlowski]

What is the sub-floor?

[rosie read n' post]

it will be building grade 4X8 sheets.

[Heathcliff]

goldfish

Good point. I was thinking you'd avoid staining the ceiling below, but if it turns your oak flooring black instead, that's a worse outcome.