Hello. I am Brian. I have recently purchased the small house plans. I have been researching items in the purpose of preparing for the future build. I am in Montana, central, and have been researching vapor barriers. I have an understanding that I should put my vapor barrier on the inside of the structure. I have noted that a lot of the builders on this site use a tar paper on the outside of the OSB prior to the application of there siding. My question is what is the point of the paper? Is it factory recommended per siding manufacturer? Would "tyvek" perform the same purpose? I am an electrician, and have never seen tar paper under siding on newer homes.
Thank you for any input, and education.
Sincerely,
Brian
The #15 felt on exterior walls is called a weather resistant barrier in the building codes. It's purpose is to block air infiltration and liquid water. It is not a vapor barrier.
Vapor barriers are things like polyethylene plastic sheet or a vapor retarder like the paper on batt insulation, would be installed on the inside of the framing once the wall cavities have been insulated, in your climate.
Tar paper was the norm before manufacturers developed the synthetics like Tyvek. There are varying opinions on which is best. One big feature of the synthetics house wraps is they are light weight and come in 9 foot wide rolls. It's quicker for a work crew to install housewrap than to do the job with tar paper (building felt). Hence contractors like it.
w*, Your first few sentences sound like an AA meeting intro.
MD types quicker :)
You are required (and its a good idea) to have a weather resistive barrier over the framing or sheathing and under the siding. water will at some point find it's way back there. Housewraps do a great job of keeping moisture and wind out. They do less well at letting any moisture that happens to condense behind them get out. Tarpaper is more fragile, has more joints so is a less good air barrier, is rapidly damaged by UV, etc. It does a great job of swelling shut when wet and drying taught and porous when dry. It can trap and hold a small amount of moisture within itself and act as a buffer. I can sit on either side of this discussion depending on the day and my mood.
Thank you for the replies. I had a good laugh at the AA nudge. It is my first post, and was introducing myself in a way. Thanks for the laugh. I will have to check the price of "tyvek" verses felt. I thought it may be a matter of pride for materials in this matter. Would anyone recommend one over the other?
Brian
I spelled pride instead of price.
Brian, there should be a "modify" link in the upper right side of any post you make. That lets you edit your own errors. I use it a lot. ;D
I pretty much lean in the direction of #15 felt for walls. [noidea'
Felt will cost you less than 1/2 of what Tyeck / Typar will run I'd guess. Like Mtn D, said it's labor that make GC's use the 9' rolls and in some ways "pride" is involved as clients want what " The Jones have on their place!".
That being said if your labor is "free" and you can cover / side as you go, felt is time proven to work well. The wraps have a "rap" sheet of failures due to a variety of reasons .
I've used lots of both and IF the siding is Cedar I'd much rather see felt used. The Cedar oils and as the report calls it " sulfiacants" (sp) dirt , cedar saw dust , etc , "plugs up the hole" in the wraps allowing moisture to bridge or pass thru the wraps and get into the or on the wall sheathing. Think of the wraps as Gortex , dirty Gortex is useless, dirty house wraps are also useless.
If you decide on using one of the wraps , use Typar or Tyvek, not one of the "has the lumber yard logo on it" wraps or a "no name" wrap. I've seen some really bad results with the off brand house wraps.
Good luck and w* to the forum! PEG
PS : Some of my above are laymens terms for how the wraps work , there a extensive study done by MIT, IIRC, that if you Goggle "house wrap issues" you should fine where these things are talked about.
My only answer would be, pay attention to PEG688 w*
Oh yes, we used felt on our house.
Another thing to do is to check with the building inspector and see if they have a preference. If they don't like tar paper you would hate to have to remove the siding and start over.
Not much worry of that happening, at least here in NM. The weather resistive barrier has its own inspection, which is after the framing inspection and before the barrier is covered.
Thanks for the advice folks. Again, I accidentally typed pride instead of price, I am not the pretentious sort. I do not have to deal with inspectors, as there is an exemption for this type of building. All of your input has helped me. Thank You