Replies

1. 
   xxPaulCPxx | Aug 15, 2012 05:31pm | #1

   Describe your proposed wall system, layer by layer, from the studs out.

   You shuld only use one kind of building paper, but you should take care to flashing and air sealing details.

1. 
   tcleveen | Aug 16, 2012 02:22am | #2

   wall description

   It's a 1950's house and this is the end wall of a 26 foot long by 18foot   wide living room. Diagonal 1x8 fir on top of nominal 2x walls, uninsulated. Repleacing weathered cedar shingles with similar appearing cement board GAF shingle panels only on end wall. Covering diagonal wood with 3x8 plywood for a little shear strength and nominal insulation value. Don't want to build walll out any further due to window and other trim issues and because I'm leaving cedar shingles in place on a contiguous right angle wall.  Thought I'd Tyvek my new layer of plywood and then overlay with felt.

1. 
   workman67 | Aug 17, 2012 09:58pm | #3

   I like your question!! I have a house built in the 1930's and whenever i do any cedar shake repairs, I find that the old tar paper is still in good shape. I still have the original cedar shake and cedar clap board on my house with no insulation in 80 percent of the house and all is well with my structure!

    I always wondered why big contractors would use tyvek on buildings everywhere when i thought that it was really formulated primarily for vinyl siding. I have read that it is good for use even under fiber-cement BUT I did my brothers house over in fiber-cement a few years ago, and we just used tar paper. We did sheet the whole house with 1/2" CDX first though.  I would say it wouldnt be a bad idea to go ahead and use 30# felt because of the old lumber sheeting but i have to say with all the old houses that i work on, tar paper is still my go to material!!

   Don't fix it if it aint broke!

1. 
   DanH | Aug 17, 2012 10:29pm | #4

   The main difference between builder's felt and housewrap is that housewrap, properly installed, is a virtually 100% effective air infiltration barrier.  Builder's felt is far less effective.

1. 
   tcleveen | Aug 18, 2012 01:41am | #5

   ok- I get the difference but wondered if there was any added benefit or negative to appllying both- as I thought I'd get a modest benefit in restricting air infiltration and I don't want the time or expense of drilling holes in each stud bay and blowing in insulation. I thought I might have heard somewhere that the cement board mfgr didin't recommend the new building wrap used under their cement board siding and preferred asphalt paper but I'm not sure of that.

2. 
   DanH | Aug 18, 2012 07:47am | #6

   Some feel that builder's felt stands up to the weather better, if the siding is not reasonably watertight.  Additionally, there are some claims that housewrap can be degraded by contact with other materials, including cedar siding and builder's felt.

3. 
   tcleveen | Aug 18, 2012 02:25pm | #7

   Thanks for the feedback. I'm going with a first layer of Tyvek, then 15# asphalt paper on top of that, then the cement based shingls from GAF and hope for the best. At least that way the felt paper is next to the shingle product which I think the manufacturer prefers.