when do you use builder’s felt versus when do you use tyvek as an underlayment to your finished exterior???
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You can't use Tyvek under cedar....THE top end builder near me "only" uses felt paper and I'm right next to him on that one...there's still something about wrapping a house in plastic that irks me.
I wrapped my house.the additions that is under cedar before I heard that its a no no.
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a...
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that's interesting. interestingly enough, i've seen my company wrap additions in tyvek and then cedar clap over that. do you know why tyvek can't go under cedar? also, i've seen alot of construction that doesn't get either tyvek or felt... just behind doors and windows. is this a frowned upon practice or perfectly normal???
Cedar and some other types of wood leach out tannins (sp?) as they go through the wetting & drying process. These are acid like chemicals that deteriorate the house wrap.
As far as not using anything at all as a rain screen between your exterior cladding and your sheathing - yea, well there is always someone who really doesn't care about quality, and does not understand the basics of making a structure weatherproof. Next you are probably gonna tell us that this was on a vinyl siding house with OSB sheathing... Not that there is anything wrong with OSB except that it is not as water resistant as, say, CDX plywood. Matt
There appears to be significant disagreement as to whether you can use cedar over Tyvek. Nothing official says you can't, if I recall the last couple of go-rounds, but there is either an "urban legend" or "common knowledge" that you can't, depending on where you stand.
http://www.cedarbureau.org/faqs/felt.htm#quest7
Would you recommend house wrap or felt for shingle sidewall application?The CSSB recommends Type 30 roofing felt. House wrap typically allows moisture to flow behind the shingles, where Type 30 roofing felt will not.
i've seen alot of construction that doesn't get either tyvek or felt... just behind doors and windows. is this a frowned upon practice or perfectly normal???
Normal for hacks at work again.
At 1st my sentiments went along with yours, but the more I thought about it, is it possible that thebozer has looked at homes under construction just before or after the windows and doors are installed?
If that is the case, and it is quite a common sight, it would be easy for one who didn't know that 1st you wrap the openings then you install doors and windows then you wrap house, to assume that the only wrap is that which is visible around window/door openings; as the house has not actually been wrapped yet.
I have a sneaking suspicion that is what has happened here. as I doubt a house could ever get away without some sort of wrap. unless it were somewhere up in the hills in the back woods.
then again ya never know....least I couldn't see that happening around here.
you may be right. i may be crazy.
Some model building codes do not require sheathing wrap under certain exterior claddings. But just because a BC doesn't require something, doesn't mean it's a good idea. I'd bet they also don't require that your kitchen have a sink in it... Matt
You can use Tyvek under cedar, as long as use leave a space for airflow, which is a good idea no matter what you use for wrap. I was curious about the cedar-Tyvek issue a couple of years ago so I called the Tyvek rep. Apparently the tannins do not deteriorate the Tyvek, but they alter the molecular structure of the water, breaking it down and allowing it to pass through the pores of the wrap. That was his explanation, I'm not even sure if it's scientifically possible, but it's just one more reason to fur out my siding. By the way there's an interesting product by typar that is a house wrap covered with a stiff mesh that creates a 1/4" gab behind the siding, looks like a pretty slick system.
One more note Tyvek is not plastic, in fact it is much less of a vapor barrier than tarpaper, in my opinion the stuff is awesome when used properly.
Cedar tannins don't "alter the molecular structure of the water", but they may help liquid water leak through the pores by acting as a kind of surfactant (detergent)- perhaps that's what the guy meant.
Tyvek/Typar are supposed to be permeable to water vapour (i.e. humidity) but resistant to droplet leakage because the material is hydrophobic (i.e. it makes liquid water bead on its surface). That tendency to bead off water is pretty limited though, as anybody who has worn Tyvek coveralls in a rainstorm will know. And any amount of contamination of a soapy nature will allow liquid water to wet the surface and possibly leak through the pores. Maybe that's what the cedar juice does over time. Maybe that's why they prefer a truly impermeable barrier like asphalt-saturated felt behind cedar siding.
"One more note Tyvek is not plastic,"Then what is it?" Some brand names are Tyvek, Rufco-wrap, Barricade and Airtight-wrap. Their intent is to minimize the passage of air, while still allowing water vapor through the exterior skin of the building.Three basic types currently are available. Tyvek is a spun-bonded polyethylene. This is a mat of polyethylene fibers spun-bonded in a patented process. The second type is perforated polyethylene film. The third type is spun-bonded polypropylene, a different type of plastic.
Each of these can be effective air barriers if installed according to its manufacturer's recommendations."http://www.engext.ksu.edu/ees/henergy/envelope/infiltration.htmlPolyethylene certainly sounds like plastic to me.
Each of these can be effective air barriers if installed according to its manufacturer's recommendations."
Before, one presumes, one knocks all those nails through siding or shingles or masonry wall ties into the sheathing & structure under the house wrap?
And, true enough, any felt paper installed is equally perforated; I just have to question any material that has quite that many holes in it.Occupational hazard of my occupation not being around (sorry Bubba)
While I believe what all of you say regarding Tyvek under Cedar (and not wanting this situation) I have to say I have never (that's NEVER) seen a single house built around here or re-sided that has firring strips over the Tyvek before the Cedar shingles or Clapboards go on. Maybe I'm missing that step but ever since reading this on another thread I've been looking and nobody seems to do this.Tom
Anytime you are siding a house with wood, clapboards, shingles, shakes, you should use red rosin or 15# felt paper (rosin paper is actually the better choice.)
Using Tyvek house wrap for these applications doesn't allow for proper ventilation of the wood. The house wrap will actually hold moisture on the surface and cause the wood siding to fail prematurely.
Tyvek wrap can be used for all other applications, vinyl, aluminum, cementitous, fiberboard, etc.
-CARPENTERDON
Dimensional Carpentry & Custom Woodworking
I beat the competition Hammersdown!
Edited 6/28/2005 8:16 am ET by CarpenterDon
The best quality of layering I have ever done, was half inch plywood sheathing, 30lb. felt, Home Slicker, Cedar siding, stainless steel staples, with the cedar shingles primed and stained. I hope to be long gone from this earth before any work needs done on that particular siding. The Home Slicker is correct in stating that the home needs to breathe.