Is sheathing wrap required or necessary?
We saw a house this weekend that we like a lot. The house has a fiber cement siding exterior with some kind of composite trim boards for exterior trim. I noticed that the builder had not used anything under the siding. It was just nailed directly over the wall sheathing. I was able to tell as I expected to see house wrap, tar paper or something when I looked in the gap between the wood window jamb and the 2×4 framing around the windows. This was in the gable ends of the attic which is unfinished. I could not see what the deal was with the rest of the house as it has the drywall and interior trim installed and is all painted and nearly done. The exterior is done too. It appears that they use OSB wall sheathing – or at least that is what I saw on the short walls in the (taller) back part of the crawl space and on the interior of the gable end walls in the attic.
It is a small custom builder so I called the builder directly and asked him if he had used housewrap or some kind of weather barrier under the siding. He said “No we do not use house wrap or anything under the siding other than wall sheathing. It adds about $1000 to the cost of a house and it is not required by code. House wrap is still a relatively new product and it has not been shown that it doesn’t cause problems. You don’t want to make a house too tight. If you trap moisture in the walls it can cause mold. You know how worried everyone these days is about mold.”
He then said that he would be happy to talk further about the house or help me with anything I needed and would like to have us as a customer.
I said, “OK, thank you.” and we said goodbye and hung up.
By the way, I did some quick research and the current building code here is the NC 2006 residential code which is based on 2003 IRC with NC amendments. The house was started in 2007.
Your thoughts or direct experience is greatly appreciated.
We live in central NC if that matters.
Replies
Even if not a code requirement it is good practice for most situations.
House wrap like Tyvek is not a vapor barrier, it is an infiltration barrier, so trapping moisture would not be a problem.
The builder is a fool.
Wrap may not be required by code (I'd have to look it up), but without the wrap, you can't properly flash the windows and doors to keep the moisture out.
Plus ANY little bit of rain that gets thru any joint of the siding will eventually work its way into the structure. And in a driving rain, quite a bit could get in.
A number of builders here, and elsewhere, are going back to 30# tar paper as the housewrap. Its got a very long, successful track record, is reasonably cheap, and unlike some wraps, like Tyvek, isn't affected by cedar siding.
If he had properly installed and flashed a housewrap of some kind, he wouldn't have to worry about moisture getting into the house and creating conditions for mold. Now he does.
I wonder if he used felt under the roof shingles?
try looking at 703.2 of the 2006 IRC for the requirement. 15# is the min.
Edited 3/30/2009 5:56 pm ET by john7g
I've got the book, but was too lazy to find it and look up the code <G>
I'd find a different house & builder if you could. In theory you could make it work with a lot of extensive maintaining of the paint and caulk but I doubt the theory would be perfect.
Could you see any flashing where you were looking?
it might fly in New Mexico or West Texas, but not in NC. He is inviting mold.
NO siding system is water proof, so a lot of moisture is driven into a siding surface on the wind. The only way to keep it out is with properly installed housewrap or tarpaper. This is strictly a cost saver for the builder and no way to build a quality home.
Keep in ind that code is a set of MINIMUM standards, and not a goal of assured quality
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Tale a look thru this thread at the pictures and text. The main cause of rot in these was poor wrap and flashing detailing, rather than the windows mentioned.
after reading that thread, if you still want a house with no wrap of any kind, you have my blessing.
;)
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I'd turn quickly and walk away from that house.
And the builder.
He's a hack, run.
Joe H
I wouldn't buy a new home in Minnesota without housewrap or something I was convinced was equivalent. When the winter wind blows 40 mph from the northwest housewrap makes a lot of difference.
Dunno about North Carolina.