Rosin Paper Or Roofing Felt?

Mike Finley

I was in two hardwood stores this weekend and the subject of underlayment came up for nail down hardwood. One person recommends red rosin paper and the other guy recommends 15 lb roofing felt.

Is one preferable over the other and why?

Peladu

Mike I have always seen 15lb roofing felt used.

I only use rosin paper as floor protection..

DecksEtc

An add on question, is using either a necessity or a preference?

And, if you do use either, are they just stapled down?

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King of karpets

i use the red rosin .. I dont want to get my hands all black from the felt .. you do need to use either though .. it keeps moisture from comming up from under the wood .. Some say it also quiets the floor .. I staple a breath at a time with a hammer gun we use for carpet pad .. staple one end ,and streach the other with your hand , and staple it. a few on the seam .. you dont have to go crazy with the staples .. In jersey we have to order it along with the spline when we order the wood .. I will be out your way this summer , my Brother lives in Parker ..

ccoffer

They are both wrong. Aquabar is the best stuff to use. It comes 500 sq ft to a little roll for less than 20 bucks. It won't mark walls and it is a more effective vapor retarder than #15 felt. Rosin paper offers no benefit to the assembly whatsover.

Stapling is not the best way to do it. You are better off just flipping the shots over after you cut them. That will give you a nice reverse curl that makes fastening the VR unecessary.

dsnAK

Tell me how felt or rosin paper act as moisture barriers?

How would either stop any mosture vapor from entering with the 10,000 or so holes in it after stapling the paper and nailing the flooring? They help with a little with moisture; but if you do not address site conditions properly they will not prevent a moisture problem.

In my experience these underlayments are used to help reduce noice between the subfloor and finished floor.

IHI

Just like the old days of felt paper on exterior walls and even today on standard roofing, it does not prevent mositure since when I think prevent I thinnk 100%, but it will slow it down quite a bit So IMO, something is better than nothing and rosin paper does little other than to say you put somthing down. I've always preffered to install felt paper on top of subfloor in my remodels prior to installing underlayment so if spills, leaks whatever happen it will stop or slow process so rotting out main sub floor is reduced or eliminated..for the most part.

FWIW, when using rosin paper to cover linolium as a path to your work room...dont let it get wet, the red dye will bleed through casuing you to replace the home owners entire floor..ask how I found this out years ago

adams,b

A wood floor is going to be the first to tell you that there is a moisture problem. Water will finds its way through anything....The felt paper conforms around the staples to help seal, but like I said if you excessive moisture you have problems because it will show on your floor. We use 30# felt under all of our wood floors. They would run you plum out of town if you showed up to the job with red rosin paper.

Tom R

Could be wrong, - - the way I've always understood it is pretty much what dsnAK says, - - the moisture issues should be taken care of separately, - - the paper is just used as a (minimal) 'additional-protection' and to quiet the wood on wood. I also understand red rosin is preferred because it will outlast felt paper.

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Mike Finley

Thanks for the help guys. The install was done yesterday. 220 sq foot of prefinished Mohawk 3 1/4 wide 3/4 hardwood. I was surprised when I opened the boxes last week to let it acclimate how small the lengths were, from 12" long to the longest of maybe 5' with most in the 3-4' range, but they went together well and looked great.

I ended up using the felt paper (HD carrys it and I rented the floor nailer while there) For prep I drove in some screws here and there in the plywood floor where it might have seemed it needed it. I sanded down the edges of a few places where the plywood seams were slightly off and used a little floor leveler in 2 places. The hardest part of the whole thing was getting it square with the starting wall and making sure it was going to be square with the transition board in the door way. A 8 foot level as a marking guide and a square and a whole lot of careful measuring finally got the starter course in and from there it was pretty simple. A couple of challenges were the 22.5 degree angled wall on one end of the room and coping perfectly to the drywall trim in the doorway which had rounded corners.

The really nice thing was laying in the floor and then being done with it. Realizing that no sanding, staining, sealing was required and not having to deal with the extra time and dust issues makes me wonder why anyone would install unfinished hardwood.

Tom R

Seems like every year the 'shorts' get shorter, - - drives me nuts, - - too damn many seams, - - I explain it beforehand to the customer and have them agree to purchase 25% extra.

Also, ordering the 'select' grade tends to be finer, more consistent pieces and less shorts.

I agree pre-finished is the way to go.

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dsnAK

[QUOTE=IHI]Just like the old days of felt paper on exterior walls and even today on standard roofing, it does not prevent mositure since when I think prevent I thinnk 100%, but it will slow it down quite a bit So IMO, something is better than nothing and rosin paper does little other than to say you put somthing down. I've always preffered to install felt paper on top of subfloor in my remodels prior to installing underlayment so if spills, leaks whatever happen it will stop or slow process so rotting out main sub floor is reduced or eliminated..for the most part.

[QUOTE]

Felt on walls and roofs work differently - Gravity. Water hits them and it sheets off with the pitch of the roof or the verticle wall. A flat roof gets a different treatment than a pitched roof.

For what its worth felt is still used on walls and many people have left housewraps and are back to felt.

For a floor the main worry is moisture coming up from below and affecting the floor. If you have a major flood event you are screwed anyways and the felt is not going to save you since all of your flooring will expand and may not sit down again.

Shorts suck -I always ask the customer if they mind. Many floors can be ordered with 'longs' and you pay $1 or $2 more per foot; but they guarentee you longer pieces. Ordering 25% more may do the trick; but if you get 1 or 2 boards per bundle -that's alot of waste.


Site finished floors have their place - harder to do in remodels but still it is possible w/o much inconvenience. Use a "dustless" system and use water based finishes and you can be out of there in a few days. The water finishes can be recoated quickly ad do not stink and kill brain cells. They definately have a different look than prefinished...

Tom R

dsnAK, - - nice to have someone on board who ignores all the HYPE and PROPOGANDA and can see the 'real picture' of what works and what doesn't. You've got a lot of good and ACCURATE information to offer. Here is a GREAT example . . .



The manufacturers conveniently fail to mention that their housewraps FAIL pre-maturely because they have a chemical reaction with the wood or OSB they are applied to.

There are cases where housewrap has all but disintigrated after only about 10 years.

Good ole' felt paper will LONG OUTLAST housewrap.

Yet most HOMEOWNERS, - - and for that matter, - - most CONTRACTORS will continue to fall for the HYPE and MARKETING and insist it's a better product because the LIE has been told so many times.

Oh yeah, - - and also, - - because it's PURTIER!!

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ccoffer

The term used to describe felt is Vapor Retarder. Not vapor barrier. Felt has the ability to accept moderate amounts of vapor and slow its transmission into the surface above it. Rosin paper is worthless. Aquabar is the best option.

dsnAK

Felt will not stop moisture it will 'sheet' water. Moisture will penetrate felt as it will penetrate house wrap. That is why they are allowed on walls b/c interior moisture can penetrate them. More in a minute I had to post 10 posts before I can add a link?

Heres to #10

dsnAK

I partially agree with you - I think proper flashing is the main cause of Housewrap and siding failures. Their have been some instances where a chemical reaction was suspected but I think that is the exception rather than the rule...

My personal house has OSB - Tyvek - 3/8 furring strips and cedar siding. I am very confident that this sytem will not fail as I have created a drain plane and have paid great attention to flashing all of my openings. For me the HW was easier to install and easier to properly flash.

HW does not belong in some siding applications, I would never put cedar or some others directly on a HW.

Here is an interesting study of all of the housewraps

Here's an excerpt -

Housewrap or Felt?
Based on our testing, if I were buying a housewrap today, I would choose either Tyvek or R-Wrap, because they display the best water resistance. But so far, I've avoided the million dollar question - housewrap or felt? The truth is, there's not million dollar answer. In general, I don't think it matters a whole lot. If you get the flashing details right, and are careful installing the building paper, you will prevent 99% of the moisture problems caused by wind-driven rain and snow. Either product, housewrap or felt, will provide an adequate secondary drainage plane. And either product is permeable enough to allow interior moisture to escape.

Sorry to hijack the flooring thread and I do use felt under floors for squeaks and such and it may help a little; but proper site conditions trumps everything. Rosin paper makes no sense to me...

ccoffer

Is this a reading comprehension problem or something? No one claims that felt will "stop moisture". It will RETARD vapor transmission. That is why it is a vapor retarder and not a vapor barrier. I have already posted this before. What gives?

Mike Finley

Hey, since we are on the subject... how do you deal with air infiltration with felt?

Tom R

DuPont has already admitted that the acidity in some woods and especially the glue from OSB reacts with the chemical make-up of the Tyvek and causes a chemical breakdown.

They said they would work on these problems that have been causing the material to disintegrate.

Then they decided to 'fix' the problem they would add this statement to their literature:

"Tyvek, like all building papers, may be contaminated by building site chemicals (e.g. surfactants) potentially increasing it's wetability. Such contamination could adversely affect water resistance of all building papers and thus the overall water resistance of the wall system."

The engineers have known for 20 years that Tyvek can fail (much sooner than felt paper) when in contact with OSB, cedar, or stucco.


P.S. My aplogies for the 'hi-jack'. dsnAK, - - I extracted this (factual)information from a conversation with an architect on another board, - - more detail can easily be provided if you would like it. Just PM me.

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dsnAK

Sorry I missed your description which I agree is accurate. I was remembering the above posts when felt was likened to a MB.