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Kate24 02-22-2012 04:43 PM

"Green" hardwood flooring underlayment and moisture barrier question
 
We are about to install solid, nailed-down bamboo flooring over an Advantech plywood subfloor. The room is on the second floor over, i.e. over a conditioned space.

We have been told we need a moisture barrier by code, and should use Aquabar, but we would rather not use an asphalt-based product, and also don't understand why there needs to be a moisture barrier when the space underneath is conditioned. We'd rather have our house breathe.

So my question is: Is it true that we need a moisture barrier by code if the floor is installed over a wood subfloor above a conditioned space, and is it even advisable to have such a barrier?

Are there any non-tar-based alternatives for underlayments?

Thanks in advance!

user1007 02-22-2012 06:07 PM

If code says you need a moisture barrier it serves no purpose to ask us why. And you can fight City Hall but plan on taking the next year off.

I've seen it required for laminate and engineered floors but it does seem strange in your instance. See if they will let you put down cork and accept it as enough of a barrier in your case. Or a simple moisture barrier and then cork on top? It comes in differing thicknesses. It will help quiet the floor too.

Something like this if they push for a moisture barrier? Never used it but it sounds like a nice alternative to petroleum laced products. There must be other such products.

http://www.greenbuildingsupply.com/A...Moisture-Block

Kate24 02-22-2012 08:33 PM

Quote:

Originally Posted by sdsester (Post 860509)
If code says you need a moisture barrier it serves no purpose to ask us why. And you can fight City Hall but plan on taking the next year off.

I've seen it required for laminate and engineered floors but it does seem strange in your instance. See if they will let you put down cork and accept it as enough of a barrier in your case. Or a simple moisture barrier and then cork on top? It comes in differing thicknesses. It will help quiet the floor too.

Something like this if they push for a moisture barrier? Never used it but it sounds like a nice alternative to petroleum laced products. There must be other such products.

http://www.greenbuildingsupply.com/A...Moisture-Block

It was a contractor friend who told us about the code, not the city. We don't have, and do not need, a permit for a hardwood flooring installation. So no inspectors involved, and we can do what we want, but we want to do it right.

Since code usually makes sense, I am questioning whether it is really true that you have to have the moisture barrier in our situation. I wasn't able to find any reference to this regulation online. I have, however, found a couple of websites where it was mentioned that you do not need a moisture barrier if your wood floors are installed over a space that's the same climate as the space above. So I'm not sure who's right here, and I was looking for confirmation, with respect to code, of one opinion vs. the other.

I'll look into the product you linked, thank you for that, and I have thought of cork, but as far as I can tell it's not a moisture retarder, or is it? And what about something like Quietwalk? I know the asphalt products are industry standard, but there must be other people who are concerned about outgassing, and want a greener product.

MNsawyergp 02-23-2012 05:20 PM

You might want to check out the following site...I have seen rosin paper used as a "barrier" also. The other purpose besides moisture barrier is that the paper prevents squeaks.

http://www.doityourself.com/forum/so...-flooring.html

joecaption 02-23-2012 05:28 PM

MN is right on. Wood to wood contact will squeck.
Cork would be best just expancive, it's a moisture barrier and does make a big differance in the sound tranfurance to the room below.

Kate24 02-23-2012 06:26 PM

Thanks to you both for your responses. I had been thinking about rosin paper, and maybe that's what we'll use. Cork sounds nice but seems too expensive.

From what I have read, rosin paper does not provide much of a moisture retarder, but it might help with the squeaks. I am increasingly convinced that we do not need the moisture retarder or barrier if the wood is properly acclimated and installed over a fully conditioned space. I suspect contractors want to put down the moisture barrier in these situations to compensate for lack of acclimation...

JetSwet 02-23-2012 06:44 PM

I have heard as well red rosin paper isn't ideal for bamboo but I've also herd that rosin paper doesn't prevent squeaks and that's from mike Holmes. What I can Say is if you do use advantech screwed down properly with galvinized screws will be much pointless to put the paper down anyway.

Sent from my iPhone 4 ios5

Kate24 02-23-2012 06:49 PM

Do you know why rosin paper is not supposed to be good for bamboo, as opposed to hardwood?

I've also read that the prevention of squeaks through underlayment is a myth, because the squeaks come from the subfloor and the screws. Our advantech is screwed down with deck screws (not galvanized but coated), and it doesn't squeak at all. It's solid as a rock.

joecaption 02-23-2012 07:37 PM

Contact the manufacture of the flooring or at least go on line and check there install directions. No wood flooring company I know of whould suggest not using a vaper barrer. If there is non and the floor starts to cup or squeck you will wish you had of spent that extra few dollars.
Your trying to reinvent the wheel here and it will not work out in your favor.

Kate24 02-23-2012 07:43 PM

I have contacted the manufacturer, and they didn't have any particular instructions. It's not about an "extra few bucks", it's about not wanting an asphalt product in my bedroom. And I'm not trying to reinvent the wheel - there are plenty of references online to using red rosin paper under hardwood flooring, and also a few references to the fact that a vapor barrier doesn't really make sense when there is an equally conditioned space below.

I will gladly use a vapor retarder if someone can suggest something that isn't asphalt-based, and that isn't a vapor *barrier*. Maybe we should go with cork, although I'm not sure how much better that would be in terms of vapor retardance than the red rosin paper.

framer52 02-23-2012 07:56 PM

This whole discussion is pretty funny.

First I know of no codes that require this for this application.

Second, logic with a nailed down floor will penetrate any and all moisture barriers thereby making the moisture barrier moot.

Might I suggest you talk to the local building dept instead of someone you "know'?

Kate24 02-23-2012 08:02 PM

I completely agree with you. The problem is that the friend who told me that any hardwood floor in any situation must have a vapor barrier is a professional flooring contractor... So that kinda throws off my own reasoning.

JetSwet 02-23-2012 08:12 PM

red rosin paper Per national wood flooring association is not recommended for bamboo as it draws moisture from bamboo and bamboo needs a certain level of moisture.
there are so many different opinions out there
I think it's always going to be is it for squeaks or vapor silly debate if u ask me.
Sent from my iPhone 4 ios5

Gary in WA 02-23-2012 11:18 PM

Red rosin paper is not, I repeat- not a vapor retarder or barrier. It has a rating of over 50 perms, Aqua-bar B has a rating of 0.87 perms. 3/4" sub-flooring at 0.49 perms.

You probably found this in your research:
Part II - Acceptable Vapor Retarders Over Wood Subfloors

A. ALWAYS FOLLOW LOCAL CODES AND MANUFACTURERS INSTRUCTIONS FOR
ACCEPTABLE VAPOR RETARDERS.

B. An acceptable vapor retarder is a vapor resistant material, membrane or covering with a vapor permeance (perm rating) of greater than or equal to .7 and less than or equal to 50
when tested in accordance with ASTM E-96 Method A. Installation of a vapor retarder
reduces the potential for moisture or vapor related problems, but does not guarantee
elimination of moisture or vapor related problems. Install a vapor retarder over wood panel or board sub-floors prior to installing nail down solid strip or plank flooring. Over-lap seams a minimum of 4 inches or more as required by manufacturer or specifier and local building codes.

C. Some examples of acceptable vapor retarders over wood subfloors include:

1. An asphalt laminated paper meeting UU-B-790a, Grade B, Type I, Style 1a.

2. Asphalt-saturated kraft paper or #15 or #30 felt paper meeting ASTM Standard D-4869
or UU-B-790, Grade D.

D. NOTE:

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.
From: https://docs.google.com/viewer?a=v&q...Es5xQ-i9hQGcb-

Never use red rosin paper as a floor protector when remodeling because when wet, it bleeds and stains the flooring underneath.....

Gary

Kate24 02-24-2012 07:29 AM

Thank you, Gary. I had seen that document at some point in my research, but it's good to read it again.

What they don't explain is why you need a vapor retarder when there is no significant difference in moisture between the spaces above and below the floor. That is the question I am still seeking an answer to, because if I have to put an asphalt-based product in my bedroom, I'd like to understand why. I've read about vapor retarders (here is a good source: http://www.buildingscience.com/docum...=floor%20vapor), and it just doesn't seem to make sense to have one between two conditioned spaces, but I will be happy to stand corrected if someone can explain it to me.

I also found this recommendation, which is from another bamboo flooring manufacturer (not the one where we bought):

Installation Approaches:
  • http://www.4windsbamboo.com/MWI/installation_dot.jpgNail Down Installation: Use rosin paper or foam pad under the bamboo flooring with cleat nails to hold the planks. Rosin paper is for the situation of no considerable moisture migrating from the substrate. Foam pad will provide cushion effect and it will also be used in the situation of considering the possible moisture migration from the substrate. Use the right length of cleat nails for the thickness of the sub-floor. No guarantee is applied to bamboo flooring installed over or onto particleboard (OSB is the exception). See details below. (Quoted from: http://www.4windsbamboo.com/MWI/installation.html)
Now that seems to make sense, but it is only one source, so I was hoping for support, or logically explained rebuttal, of this recommendation.


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