Vapor Barrier Under Solid Hardwood - Always?

Cascade Builder

Hi guys,

I say yes. I am working with a floor guy who says he never installs a vapor barrier under the floor on the 2nd floor of a house???? I say always install it, no matter what. I had him take up maybe 50 sq ft and start over. The product is a solid pre finished red oak. I called the manufacturer and they said always install a vapor barrier, not matter what floor, and it would not be warranted if not.

So I just wanted to see what all you other guys thought on the matter.

Thanks ahead of time.

wizendwizard

This answered itself!

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Cascade Builder

That's what I think. He seemed surprised that I even called the manufacturer, which might show some of his inexperience. Other than that, it just seems dumb not too install it, even if the manufacturer doesn't require it for warranty.

It also seems bad to have a wood to wood connection for a floor. Seems like you would be asking for squeaks in the future.

He's back on track now. At least he wasn't almost done when I caught it.

mics_54

Heck yeah...you don't want that first floor water vapor comin through the floor!

the big 12 inch

The wood floor manufacture is obviously in bed with the vapor barrier guy...Total scam...

MacRoadie

Yeah, I'd like to hear a practical explanation for that one. I've NEVER heard of anyone using a "vapor barrier" on anything but a concrete slab. Rosin paper yes, visqueen no.

mics_54

Floor sheathing installed correctly"used" to meet the astm perm rating requirements for "vapor barrier" ...not sure if it still does...and I don't feel like researching it.

Floordude

You absolutely DO NOT use a vapor barrier over a wood substrate, under a wood floor.
Asphalt felt, or rosin paper as a slip sheet, when on the second story of the residence.
You don't want wood to wood.

Moisture barriers are for going over concrete, or to cover the top soil in a crawl space. Anything else promotes dry rot.

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Cdat

Never heard of using vapor barrier until today. Imagine that?

Cascade Builder

Sorry for the confusion. Yes I mean an asphalt felt ( always prefer 30 lb myself, helps dampen sound ), or a rosin paper. Not a visqueen, which a vapor barrier is also. OR am I incorrect in calling the use of asphalt felt under a floor as a vapor barrier? That is part of it's job, blocking moisture right?

It seems like the general idea is to have the wood sealed on both sides. The finish seals it from the top, and the 30lb felt from the bottom. Wood to wood always seems like a bad idea.

Good to know what everyone else thinks.

wizendwizard

I understood what you meant. To use their words, paper materials such as felt or rosin are whats used. Any plastics would trap water or moisture under the wood, not good. Clarified? good!

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neolitic

Red rosin paper worked just fine
for a hundred years.
How much of a vapor barrier do you
have after you drive thousands
of nails through it?

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Cdat

I never knew it was meant to be a barrier. When I have to take up flooring to place inlay, the paper comes up to. I can't imagine glueing to a piece of paper would accomplish much. Maybe I'm doing it wrong? Haven't had one loosen yet, so maybe I'm on to something.

neolitic

More than one old timer told me
that it was mostly there to minimize
squeaks and groans between the
oak and the sub floor.

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Cdat

That is the only reason I can figure out too. Anything else seems like a bs line from the industry (flooring), to make an extra buck.

neolitic

Yeah, the old timers didn't know
how to say, "decoupling membrane."
Could have charged extra for the rosin paper
that way.

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Floordude

Asphalt saturated felt, is not a moisture barrier, by any means.

It retards the moisture, but it is not a barrier. It slows the moisture transfer, but does not eliminate it like a barrier, with a high perm rating.
Moisture retarder.

I have pulled up old wood flooring, that could no longer be sanded and it have news paper from 1937, between the 45º plank subfloor and the wood flooring.

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WNYcarpenter

I'm with Neo and Cdat...My understanding of paper under the floor was for squeeks...we don't overlap, or really do a very neat job (per se) putting down the paper...like mentionioned earlier... not to install wood on wood.

I also like 30# felt over rosin paper....rosin paper tears so easily.

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StinkyTheGrump

So then Tyvek would not be a good thing to use for a barrier right? Local flooring supplier recommended this for some reason..

WNYcarpenter

Tyvek would probably be a great product to use, but I think cost is the issue....I've was led to believe that the paper was for squeeks more than anything unless you're dealing with a concete slab...

The only situation I can think that would require a vapor barier would be directly over a bathroom....

I don't know....I know that we nail more than just into floor joists, so what difference does it make anyway?

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