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Lately, we keep hearing that house wraps may not be the best thing in terms of trapping moisture behind the clapboards and then subsequently blowing the paint off of the siding. Any thoughts? How about no wrap at all?
I've said it before and I'll say it again. The way that house wraps work now,I still choose felt. Everything I've ever read leads me to believe that felt's at least as good as any wrap and probably better than any wrap.
Tons of info in JLC articles. Chad
Just creating a link for Tim. Also, look in the JLC archives for Paul Fisette's article about Housewraps vs. Felt in a '99 issue of JLC. If you search this forum as far back as you can for either 'wrap' or 'felt' you will probably find a lot of discussion about it. We've beat it to death so many times here that the mention of the stuff makes me shudder. ;)
What about Tyvek behind cedar clapboard or shakes. I've always used Tyvek before and now I'm hearing that you can't put Tyvek behind cedar because of the Tanins in it. The guy at the lumber yard said he spoke to the siding rep and said it's not true.
What's the deal because everyone I know always puts cedar on top of Tyvek for years and now I here different.I want to know because I'm about to install 15 squares of primed 1/2 x 8 clapboard.
Some guys say 45 the butt joints and some guys say no. Some guys nail and some guys staple. What do you guys do?
I don't remember who wrote the article, but do a search on 'extractives' in the JLC search box. I'm sure you're going to get a hit on an article that discusses in some detail the effect that extractives from wood have on various wraps.
Today I talked to the rep from The Western Red Cedar Lumber Association http://www.wrcla.org/ the guys name is Paul Mackie out of Seattle Washington and he told me that the tyvek behind the cedar problem is not true.
It was a study done from some college kids that he thinks were from MIT were set out to prove that the Tanins and Extractives from western red cedar which is what makes the wood rot and decay resistant, eat Tyvek and they were sent out to prove that it eats tyvek and that was there goal. So they took some cedar blocks and stuck it in a bucket of water and allowed the extractives to bleed out of the wood.
Once they had the extractives in water mixture they put it on the stove they cooked it down until it was highly concentrated. then they let it cool and stuck some Tyvek in it and waited and watched. They wound up with a highly concentrated form of the extractives of western red cedar they put the tyvek in it and eventually the tyvek was compromised.
He said that doesn't reflect what happens in the real world and your dealing with a couple things that would counter act that kind of reaction even thow what they didn't replicate real world circumstances because your starting out with a kiln dried product that's pre primed on all sides, so you have water repelancey on the back of the siding which means that when you have moisture condinsation behind the siding and when it forms into droplets the siding isn't going to absorb it because it has the water repelancy from being pre primed on all sides.
The product that is used in our market is usually clear VG heart bevel siding and vertical grain wood moves the least amount and cedar moves the least amount of all wood species so you've got the most stable grade of material because it's verticle grain and it's Tight Grain First Growth and you wouldn't necessaraly get a similar result with Tight Knot Flat Grain which is flat grain and knot verticle grain and sometimes in some cases in comes from second growth trees or the tops of first grwoth trees which means the grain is going to be wider and your going to get a little more movement.
I'm a fan of WRCLA and frequently refer folks to their site. However, I'm afraid he's got the facts somewhat skewed. The research he is referring to was done by my predecessor on this forum, Paul Fisette, and his students at the Wood Technology Department at the University of Massachusetts at Amherst.
I wouldn't be too quick to discount research work done by university students. Some of the greatest scientific finds are the result of university research where students did the bulk of the work under the supervision of a researcher like Fisette.
You can read about Fisette's work directly from the links below. Since I can only paste one into the box below, just cut and paste each into your browser. Withhold judgment until you've read the articles, then tell us what you think.
Dr. Fisette's research papers: http://www.umass.edu/bmatwt/publications/by_title.html
His article about housewraps that was published in JLC: http://www.umass.edu/bmatwt/publications/articles/housewraps_feltpaper_weather_penetration_barriers. html
Follow-up research article: http://www.umass.edu/bmatwt/publications/articles/leaky_housewraps.html
The research done by Paul's students was preceded by the work of Joseph Lstiburek. I'm sure others have also done the study. I believe their results of valid if not quantitative. Joseph once stated that Tyvek will be the next class action law suit. It wasn't long before he toned it down a bit. (From my experience I have my own theories as to why.)
Joe, I take everthing I hear from a clerk at the lumber yard with a grain of salt. At least around here, they are trained to sell and that's about it. I listen but then I try to validate what they say by asking others, and then evaluating what I hear.
As for DuPont's site, consider the source. Although some people here think I'm always over the edge, I have learned from my experiences with Dupont marketing literature over more than a decade, that I must assume that everything they say is overstated unless I have a compelling reason to believe otherwise. That probably goes for most of the marketing literature.
The best info available is to connect with the engineering and research folks at the manufacturer's, if you can get past the sales people. The sales people present what they are trained to present. The engineering people usually have the facts but are usually not available to you unless you know someone and ask for him by name.
I believe that James Hardie Company marketing is equally hyped.
Joe, what is the alledged purpose of 45ing the butt ends of cedar shinges?
Paul Mackie apparently doesn't know Jack about conducting scientific experiments. ONe technique is to exaggerate the exposure, strenght, etc. so that a reaction can be more easisly detected and to expand the scale so that variations can be detected. A thorough evaluation may require some additional scalability and sensitivity analysis to accurately correlate the experimental data to the real world. But that takes a lot of time and the relationship is often predictable. When you design building components to have a life of 30 years, it takes 30 years to get "real world" results.
They is no shortage of advice about building products especially from those that gain from the sale of them. There is a shortage of facts, because many materials (non-code related) are often sold based upon a very loose relationship with the truth. Do you remember the bread company that advertised "less calories per slice" which they achieved by slicing the bread thinner? Well Tyvek's claims about moisture resistance was originally based upon the reduction of moisture laden air passing through the building envelope.
The value of Tyvek or other housewraps and felt depend a lot on the climate. Also, Codes and Standards are created by people, some with tunnel vision and some with no vision. The idea, for example, of placing a vapor barrier on the warm side of the wall, is not valid in southeastern NC. While it makes sense to put the vapor barrier on the warm side because of vapor drive and condensation, here in the winter, the air in the house is so dry that the value is insignificant compared to the summer situation where there is a hugh amoutn of moisture on the outside and the warm side of the wall is often the outside wall a large part of the time. Moisture from condesnation and from bulk water entry is much more of a threat so that we are better off putting a vapor barrier on the outside. The uniformed think that this is nuts. I don't argue about it too much because, plywood and OSB make a pretty good vapor barrier without housewrap, so it really doesn't matter. That is why you can look back through this forum and see where I have stated that felt is better for most moisture problems, but the use of anything has insignificant value except for flashing.
In other words, Except for the hope that felt of housewrap may slow up bulk water entry into a structure, I've about concluded that the use of any of it for anything other than flashing is just a waste, even for air infiltration, becasue all you really have to do is to seal the joints (air ain't going to blow through a sheet of plywood so why wrap the whole thing? Why not just wrap the joints. Better still, why not apply a viscous liquid sealer to the joints.) Why not put a coat of sealer on the sheathing to retard moisture intrusion. OSB already has wax which seems to work pretty good. I had a shed that stayed partially covered with felt on the roof and sides. Water got behind the felt. The only part of the siding to rot over the last three years while I've been too busy to cover it, is the part behind the felt. In this case the felt has caused more damage. In many ways, this shed mimics the problems we have in houses - means of water entry, speed of drying, etc.
We've got to start doing some thinking and quit relying on information from people who have an agenda counterproductive to our own.
Without trying to get off topic,Virginia just came out w/their New code on "window wrapping,exposed bandboards etc.And again I don,t know how everyone else does it but for eons when u framed a window hole you wrapped it in poly and caulked the window.Bandboards,exposed corners etc. wrapped in poly or rubber flashing.After somebodies "study"now NO poly on bandboards,corners,window holes;just a piece of poly drooped over the top of the window.The only bandboard flashed is the frontdoor and where the back deck goes. Glenn in the above post mentioned that his shed rotted only where it was wrapped and it took this long for our state,s "finest" to figure that out.How do you guys do windows etc.?
Our inspectors quit allowing the poly "flashing" about a year or so ago when they decided to enforce the wind codes for windows. The model code agencies were still going "dah?".
We are in 130 mph wind zone and many of the window manufacturers require that the nailing fin on vinyl windows be glued and nailed and the poly interfered with achieving the wind resistance.
I have never totally understood that. Now they put the windows in, then tyvek over the fins and tape them. I do not believe this is adequate flashing either, and many of the tapes do not stay stuck.
We flash windows by wrapping the entire opening with butyl rubber tape (which is burnished down with the end of an old shovel handle.) The sill is done first, then the jambs, then the headers. We install the window with nails. Another piece of butyl is placed over the header flange. The felt is run under the sill flange, and over the jambs and headers. (This requires that the felt below the window be installed prior to the window unless we want to cut in a piece and slip it under later.)
My preference is to slope the opening at the sill using a 2x ripped on a band saw before covering it so that the water tends to drain out but we havn't always done that.
We place the siding, leaving room for a 1/2" caulk joint around the windows which is usually caulked with NP-1 and installed with a 5/8" backer rod. All caulk joints are tooled with a stainless steel spatula and mineral spirits. We do not leave the joint open at the header or the sill, but provide for drainage at the base of the wall. (The wall will shed water even if the caulk is not installed but it looks better. A lot of builders are afraid of 1/2" joints being ugly but if they are masked and tooled, they look like part of the window and is beautiful and longlasting.
If the wall gets wet from a window leak in the first 5 years, my self-imposed guarentee requires that I tear it out and eat it, piece by piece.
I installed my fist window in 1995 and I havn't eaten one yet.
Your 2:09 post was one of your all time best! Manufacturers of crummy products are the single biggest problem our industry faces, and we are the ones that get sued for using them.
The California Supreme Court came down with a decision called Jimenez on Dec 6, 2002. That decision makes window manufacturers strictly liable for their products. That puts windows in the same category as dynamite, lions and tigers. You make it, it does somebody some damage, you are liable, there are no defenses, you can't blame the installer or anybody else, you are playing with dynamite when you put windows into the stream of commerce. Now if we can get a decision making Dupont liable for their housewrap, and Hardie liable for their fibercement, we may make some headway against the money grubbing charlatans.