Interior siding underlayment: does 15# felt paper really smell? Better options?

[ccgibson]

I currently have ~400+ boards of 1"x8" doug fir that was milled at my property in western washington that I'm currently drying. I have a recently framed workshop and I want to hang these vertically once I've finished insulating the stud bays.

My plan all along has been to put 15# roofing felt on top of insulation and just nail the planks next to each other.  No routing or other lap cuts planned. I'm happy with the look of this and came across this plan reading very similar posts on this forum.

But I recently read elsewhere about the *smell* of tar paper when used on the interior.  Is that a real practical concern for my application?  My wife is very smell/odor sensitive so now I'm contemplating if I need to change this step up.  If smell/oder is a concern, is there a better solution for something "black" simply to hide the insulation and help make the board gaps less visible?

The workshop exterior sheathing is wrapped with tyvek and siding hung on top of that. So I believe the paper is really serving visual vs. moisture barrier purposes.

thanks much,
-chad

[SawyerTed]

Red Rosin Paper Is a brown paper product used in lots of construction applications.  It would make a good interior underlayment.  No smell.  It is probably much cheaper than tar paper.  

[trimguy]

Welcome to the forum. Could you just paint the insulation black to achieve your visual ?

[DanielW]

Vapour barrier sounds like the right thing for the application: You should :theoretically' have it anyway for an interior underlayment (as long as the interior siding is dry) , and you can get vapour barrier/poly in black. It's very frequently used to peg over people's lawns when they want to block sunlight to kill all the grass. That'd be my choice, and probably the cheapest. Just to be clear: this is just so the cracks between boards show black? If not worried about vapour, maybe just a layer of tyvek/typar on backwards with the black side out?

[doc henderson]

YES, it will smell for a while, then you get used to it or the odor fades away.  I assume the insulation has a facing with brown paper.  It is coated with a tar on the other side as well.  If it is for visual on the interior wall, you can spray it with pant to match the color of the interior paneling.  Tyvek on the outside of the wall, so the glass can breath.

[ccgibson]

Vapour barrier sounds like the right thing for the application: You should :theoretically' have it anyway for an interior underlayment (as long as the interior siding is dry) , and you can get vapour barrier/poly in black. It's very frequently used to peg over people's lawns when they want to block sunlight to kill all the grass. That'd be my choice, and probably the cheapest. Just to be clear: this is just so the cracks between boards show black? If not worried about vapour, maybe just a layer of tyvek/typar on backwards with the black side out?

I was assuming the faced insulation would act as the vapor barrier.  I like this idea though, perhaps using unfaced insulation and then the black poly.  Do you think the black poly would reflect light at all since it's a shiny vs. matte surface?  I may be geeking out way too much on this. 

The backwards tyvek is also a good solution.  thank you!

[ccgibson]

Thank you all for the replies and help.  This forum is great.

Thanks for the ideas on just painting the insulation.  I'm not entirely sure if it's less work but I like the idea! 

[caveman]

We put up the roofing felt under a western redcedar, lap siding wall when we built the house 30 years ago.  I've never noticed the smell, and no one has ever commented on the smell.  The reason for us putting up the felt was that some of the boards had knot holes.  

[Nebraska]

I'm sitting on a floor that has tar paper under it, seems like you could smell it a few days. 15 years later nope. I understand the wife's nose thing....

[Southside]

Well the smell are VOC's off gassing, same thing that Chinese drywall does, so it is something to be aware of. 

[doc henderson]

just paint the paper on the insulation dark brown or whatever color will match/hide the cracks.  they should be small if using dry wood.  Am I correct that this is all for the interior side of the walls?  Tyvek on the outside with siding.

[SawyerTed]

Here's a link to uses of red rosin paper.

https://www.wrmeadows.com/red-rosin-paper-multi-purpose-building-paper/

It's good stuff when something as heavy as roofing felt is not needed.  

I use it between subfloor and hardwood flooring as a squeak prevention.   I also tape it down on floors that need protection during renovations or construction.  It is a heavy paper for masking prior to painting or stucco work. 

It is plain unprinted brown paper heavier and stiffer than a brown paper grocery bag.  Cuts easily with a utility knife. 

It is not waterproof. Depending upon the source some say it is a moisture barrier but I don't count on it for wet locations.  

Plus it is inexpensive compared to tar paper/roofing felt.  At $18 for a 3'x167' roll it goes a long way.  

I suppose it can be painted.  

[Sod saw]

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Welcome and have fun with your project.

Since you have not let us know where you are located, I am assuming and this information is for folks who are heating in the winter because it is cold outdoors.

In a heated building you should always install a vapor barrier on the inside (heated) of the exterior walls.  

Fiberglass with craft paper is not a satisfactory vapor barrier.  It will leak air and moisture thru the edges of the paper even when properly stapled to the inside edge of the studs and overlapping.  That moist air will condense on the inside of your siding and over time that moisture will rot the structure.

6 mil, or thicker, plastic is an inexpensive solution to the vapor barrier issue but will still leak at edges of windows, doors, outlet and switch openings.  Taping the plastic joints helps as doing so at window and doors helps too.   There are also other vapor barrier products available if you wish to reaserch.

As stated in posts above, the plastic can be black to help with your visual joint concerns. 


Please feel free to fill in your information so others can know your location.


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[DWyatt]

Adding to what @Sod saw stated. Know the assembly of your existing wall. If you are in a cold climate (Climate Zones 4+), a vapor barrier may be a good option. If you are in Climates Zones 1-3, a vapor barrier could be detrimental to your wall assembly. Your walls need to have a side that they breathe towards to prevent condensation within your wall assembly.

[ccgibson]

So here's an update on my situation: I'm inching towards insulation and had a local insulation company come check out my project and give me a bid (I heard from a friend some of the insulation companies are as cheap as DIY).

Anyway, he strongly advised against a black poly layer (between unfaced insulation in the walls and the 1x8 siding boards I had milled that are currently drying).

I'm in the Pacific Northwest, Mason County to be exact (south of the Olympic Peninsula) and according to him in Mason and Thurston county plastic is actually prohibited in the walls since it will cause so much moisture build-up given the crazy humidity of our climate here. He really advocated for something that can breathe to keep condensation from forming.   

He suggested a few things:
- Unfaced insulation then FSK vinyl sheets.  What they do in a lot of industrial or commercial jobs.  This is white on one side and reflective material on the back.
- Unfaced insulation in walls then OSB before my milled siding. 

The FSK vinyl sheet actually seems pretty good for what I want - manages the moisture and gives me a layer between the insulation and my milled siding.  The problem is it doesn't come in black; do you all think the white would be look strange through plank siding with gaps (again I'm not planning on routing or overlapping any edges of the siding).

I asked about Tar paper and he was weary of this given the strong need for breathable barrier for moisture in our region.

I'm meeting with another insulation company in the weeks ahead.  

[LeeB]

Any new home construction on your area you can look at to see what they are doing?

[doc henderson]

so does the FSK go on the exterior or interior side of the insulation?  Is it a vapor barrier or does it breathe?  vinyl sheets sound like a vapor barrier.  you do not want vapor barrier on both sides of the insulation and just on the interior side.  sounds like it goes on the "outside" and over the osb and under the siding.  house wrap would breathe and let moisture get out of the insulated space.

[ccgibson]

so does the FSK go on the exterior or interior side of the insulation?  Is it a vapor barrier or does it breathe?  vinyl sheets sound like a vapor barrier.  you do not want vapor barrier on both sides of the insulation and just on the interior side.  sounds like it goes on the "outside" and over the osb and under the siding.  house wrap would breathe and let moisture get out of the insulated space.

Interior side and it does breathe.  The advice was definitely wanted something breathable between the insulation and the milled siding I plan to install.  

[doc henderson]

well, I may be missing something, but you need a non-breathable layer between the wet wood inside and the insulation, "vapor barrier" and a breathable layer on the outside of the insulation say under the exterior siding.  if moisture gets into the insulation, it is no longer insulation, unless the moisture can escape to the outside.  the backing paper on faced insulation has tar on it for that reason "moisture barrier".  the house wraps that go over the osb and under the siding on home construction is breathable.  either of these slathered in roof coating, will be non-breathable.  does it have a foil face?

[Sod saw]

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ccgibson,  Making a new building takes a lot of time (labor).  Here is a way to extend that time and have the building process take a little longer.

If you are considering a hard surface (OSB or plywood) under the board siding on the outside of your building, and since non breathing plastic is always a bad idea.  Is there any reason that you can't make that black plastic breathable?

I trust that your board siding will have straight edges next to each other with small gaps between each board and you wish to have a black appearance between those siding boards.

Can you make narrow strips of black plastic and staple them to the sub siding (OSB or plywood) behind the spaces of the the siding boards so that the plastic has big gaps between strips of plastic to allow air and moisture movement.  No vapor barrier existing on the out side of the wall, just as black joint.

Another (goofy) thought.  Do you have a fabric store near by?  Do they have any black woven cloth (synthetic) that you can buy and install behind your siding boards?  I expect that the labor to cut these into strips would outweigh the cost of extra fabric to have it cover the entire wall section(s).  But it would breathe.  And since it is Halloween today, Black is the proper color of the day, right?

As Doc stated, You still should have a vapor barrier on the inside (warm) side of the insulation.


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[doc henderson]

could do ship lap or board and batten.  you really then do not need the osb, just a breathable house wrap outside the insulation and under the siding.  on the interior side of the insulation, you need tight joints slathered in roof coating.  think could hold water like a bathtub.  the inside of the insulation could have plastic and should not breath.  I am not sure our terms are crossing over.  the construction so far is excellent.

[doc henderson]

 



we may be saying the same thing, but if not, maybe this will help.

[LeeB]

Another thought might be landscape cloth. It's black and certainly breathes. 

[barbender]

I used tarpaper under our hardwood flooring. My wife has a sensitive nose, too. We could smell it just a bit when I was installing but not after the floor was in. Of course the floor got polyurethaned once installed so that masked the tarpaper smell, but it's nothing we've ever noticed after the construction phase at any rate.

[doc henderson]

Hey guys, I thought I was working on the building a Kiln thread.  My comments were directed at that.  My apologies.  Doc.