Housewrap was installed directly over stubs. House was built in 1999, Jacksonville Florida. I am replacing rotten particalboard type wood siding. Under the siding is sheathing (OSB) and then some type of housewrap installed under the sheathing directly on the wood studs.
There is no barrier installed between sheathing and outside siding. As a consequence, sheathing is also damaged and will need replaced.
What purpose was served in installing the housewrap directly over the studs? This left the sheathing unprotected.
What is the best way to repair this situation. I am thinking about replacing all the particalboard siding with cement board siding and will also need new sheathing in many places due to sheathing being rotten.
Should I just leave the original housewrap on the stubs and install another housewrap over the new OSB Board to protect the new board and then continue with the cement board or will this pose a problem becaue of having the house wrap on both sides of the OSB Board.
At a loss as to how to reapir this situation?
Replies
This house wrap you speak of may be a true vapor barrier. In southern climates where the inside is colder than the humid outdoor climate a vapor barrier may be placed to the outside wall surface. This keeps the insulation and outside wall cavities dry. So I would leave the existing house wrap intact.
I would use felt on the outside sheathing though. Hardie plank is a great siding too.
As MarkH said, in warm, humid climates, vapor retarders should go on the exterior of the wall assembly.
Whether or not this is actually a 'vapor retarder', however, remains to be seen.
Most housewraps are not vapor barriers, and in fact are designed to not stop or restrict the flow of water vapor from passing through them. Most housewraps are designed as air barriers or weather barriers. A few (like Tyvek) are listed as both.
That said, one must know how the material or membrane is classified before using it for the intended purpose.
One should never install a vapor retarder on both side of a wall assembly or sheathing because trapped vapor can condense between them, have difficulty drying, and cause rot and mold growth.
For your climate you might consider instead using rigid foam insulation under your new siding and over your new sheathing. It will act as a true vapor retarder, a true weather barrier, and provide added energy efficiency.
Luck.
The primary purpose of housewrap is to serve as an air barrier. It only became practice to use it as a moisture barrier after the fact. Many homes (including one I remember on TOH) were built with the housewrap under the sheathing. (Claim is that it protects the wrap better, though I'm not sure I believe that. It does allow the wrap to be more lightly fastened, but I can't see that that's a big advantage, in cost or function.)
Having a layer of housewrap on each side of the sheathing will not cause problems, or you can apply felt to the outside. Tape any tears in the old wrap if you go with felt.