I drove past someone else’s job yesterday. It’s a stick-framed garage and it appears that the exterior siding will be resawn plywood (T-111 without the grooves). The guys doing the work had, as far as I could see, put Tyvek up directly over the studs and then put the resawn plywood over the Tyvek. The interior of the building is clearly visible from the street and there’s no mistaking that bright white Tyvek look between the studs as seen from the inside.
I don’t get it. If it were my building I would prefer the back of the plywood open to the interior so that moisture could dissipate. On the other hand maybe the Tyvek will breathe and help stop air infilatration… but in a garage? Been forever since I put plywood siding directly over studs, so I dunno.
Replies
Moisture will pass right thru the Tyvek but air will not.
You get out of life what you put into it......minus taxes.
Marv
This person will probably be insulating the garage at a future time and wants to make sure that there is a moisture barrier between the plywood and future insulation. Tyvek is a breathable house-wrap so it shouldn't cause any harm to the back of the T-111 ply siding. Since this siding only has a lap joint than there is always a possiblity of water infiltration. In my mind since so many people are hasty to make short cuts for the sake of quality, overkill is always better.
What's the quandary here ?
Tyvek or tarpaper goes on just before the siding.
In this case, the siding went directly on the studs. Therefore, the tyvek also went directly on the studs below the siding.
Live, Love, Forgive and Forget
Quittin' Time
"...perfectly good Tyvek?"
Just from reading this board, I would've thought that was an oxymoron.
Rich Beckman
Another day, another tool.
This is from the tyvek web page:
Tyvek¯ Breathes -- A critical feature for a home’s wallsMoisture Vapor Transmission Rate or perm rate of a material determines the ability for water vapor to diffuse or evaporate through the wall. The higher the perm rate, the more "breathable" the material is and the easier it is for water vapor to pass through. Materials with Perms below 1 are considered vapor retarders since the rate of moisture vapor flow through a 1 Perm material is so low there is essentially no flow. Tyvek¯ has a Perm rate of at least 58 Perms which is very open to allow moisture vapor to flow through.
Tyvek¯ HomeWrap¯ has the best combination of air and water resistance, plus breathability of any secondary weather membrane available.
OK, so that is their sales pitch, take it for what it is, but personally I've bought into it. If you look at a piece of tyvek under a reasonably powerful magnifying glass, it looks like a furnace filter - a collection of fibers in a random pattern - not woven - and it's NOT a piece of plastic film. It is designed to block liquid water droplets, thereby acting as a rain screen or drainage plane, but still breaths, while still blocking the wind. If I had a time machine, one of the things I'd be interested to find is what the outcome 25 years from now will be, but I say use it. I've read articles that rated Tyvek as having among the highest perm ratings of the house wraps. I consider the perforated poly brands of house wrap inferior.
Some argue for using tar paper, and I almost think it's a flip of a coin, except that Tyvek is quicker to install. Tar paper has the advantage of that it tends to seal around nails. It's perm rating is about 1 for 15# felt but once you factor in the (lapped) seams every 3', the perm rating is probably considerably higher (a higher number = more ventilation).
As to the original question, the guy is likely, planning on insulation, but even if he is not, I think that it is important to have a rain screen under neath your siding - so that if there is a leak, the "white wood" framing will have some protection. That said, since Tyvek degrades with exposure to ultraviolet light, having it "see daylight" for a long period of time in his his garage may not be the best idea.Matt
Matt -
Here's a little experiment I did with Tyvek:
Take a small cardboard box and line it with Tyvek. Fold the corners like you'd fold a shower pan so it will hold the water - no seams at the corners. Fill the box about 3/4 full of water. Let it stand for a day or so .... in my case, no water came through the Tyvek.
Now take your finger and wipe across the bottom in a few places. This breaks the capillary surface tension of the water. The box should leak like a sieve. Mine did.
Tyvek appears to be "waterproof" as long as there's nothing to cause the break in the surface tension of the moisture. On very close examination you can see extremely small perferations in the Tyvek.
Typar, what my framer used to clad my new shop, does not behave this way. It's waterproof. Period............
Dennis in Bellevue WA
[email protected]
So how do you install Tyvek without a capillary break? If I understand you correctly, you are a fan of Tyvek. But wouldn't your sheathing/studs/etc. provide a capillary break, thereby causing the Tyvek to "leak like a sieve"?
Jon Blakemore
Jon -
If I posted something in the past to give you the impression I was a "fan of Tyvek", I'm sorry; I certainly had no intention of doing so and no, I'm *not* a Tyvek fan. In fact, I made the framer who enclosed the kithen corner buildout in our remodel project remove it in favor of 15lb felt.
I did put Typar on the 24x40 shop that I built this past summer. Still no siding on it yet and after all the wind and rain we've had up here lately (Mt. Vernon WA area) I see no signs of moisture migration into the OSB sheathing. I would have prefered felt over the Typar but that's what the framer used and it's staying put a lot better than felt would, with only staples holding it in place. That's the one drawback of felt - you gotta get it covered or it will be gone in the first stiff wind.
...........
Dennis in Bellevue WA
[email protected]
Well, I'd like to do the test, and looked around and have some Tyvek "in stock" but no Typar. In order to be objective, I'd like to test both materials at the same time. There was an article in JLC "Notes" during 2/2000 that compares the performance of the different housewraps and tar paper (15# felt).
Really though, I think what is just as important (if not more so) than material choice (Tyvek/Typar/Tar Paper/etc) is that the windows, doors, corners, etc be detailed properly, and that the paper be properly lapped.Matt
My understanding is that Tyvek was not designed as and is not advertised as a barrier against liquid water. It just happens that new, clean Tyvek will block liquid water, but as Dennis's experiment shows, it's not to hard to make it start passing water.
The way I read it, your quote from the Tyvek website says that it is intended only to be a wind barrier, with high permeability to water vapor, and doesn't say anything about it blocking liquid water.
Here is the url: http://www.tyvek.com/na/homewrap/english/products/sys_home.htm
If you want more objective info, send me an E-mail and I'll send you a JLC article that compares different housewrap brands and tar paper too.
Dennis: BTW - one thing about Typar is that the manufacturer guarantees it against degradation due to ultraviolet light exposure. This is good for anyone who doesn't get around to installing their siding for a long time. Matt
I don't understand why we put anything between T-111 and the studs, either David, housewrap OR felt. But I think a part of it is all the guys who's buisness motto should be "I have a computer and a CAD program, that makes me a Home Designer".
I live and work in the South Puget Sound area and I am seeing more and more prints with the detail you describe - almost has become an accepted practice around here.
The way I've seen T-111 rot is from either wicking water from vegetation too close to the bottom of a sheet, or prolonged exposure to direct sunlight/rain cycles and inadequate paint protection. I don't see how housewrap is gonna help in either case. Weather gets past your siding, I'd hate to be counting on felt paper or housewrap to protect the structural framing.
Anyone remember that Tyvec tape you could use on the seams of your subsiding in you sheeted you walls before siding them? Doesn't plywood have a permeability rating?
You said: "Doesn't plywood have a permeability rating? " Look at this web page, down around the bottom.
http://www.energy.state.or.us/code/respub/res15.pdf
Matt
that caught my eye too ...
I was surprised there's actually a "use" for it!
Jeff Buck Construction Pittsburgh,PA
Artistry in Carpentry