Is underlayment necessary for cedar siding??

[Alaskan Son]

I would like to note that I don't put much stock in what research says when I see something contradictory with my own eyes. We've had failed building products and practices over and over again throughout the years because we all simply believe what we're told instead of what we see.

How many of you have taken apart houses 5 or 10 years old built using your average air sealing and WRB methods?? I've seen more problems with those houses than I have with houses that are 30, 40, 50, or 60 years old.

No offense please, but I wasn't looking for any "solutions" or new products. Just an explanation of the reasoning behind requiring felt behind cedar.

I've seen and heard enough negative facts regarding housewraps on newer homes around here, and I'm seriously concerned that if we keep wrapping our "air tight" houses in climates like mine they're going to be rotting out in the 20 years because we can't truly stop all the air leaks in an average home and once it gets into the wall it needs to dry out. If the area isn't wet enough to really need a WRB, it seems that regardless of what code says it may not be the best idea to install it Sometimes codes need changing.

I saw one house only 7 years old that had completely rotted out on the outside 2 inches of framing and the WRB seem to be installed just fine with a proper vapor barrier in the inside. And I'm not the only one who's seen the same results.

[Catspaw]

I would think that vapor drive might be a good reason to use felt behind cedar.

I removed some cedar siding this summer. We had a period of cool, rainy weather followed by a hot sunny day which was when I pulled the siding off. There was a very significant amount of condensed moisture on the still cool housewrap behind the siding - moisture that was driven out of the back of the cedar by the sun.

With no housewrap (or felt), that moisture would have soaked the sheathing. Without a rainscreen, there was still nowhere for that moisture to go other than back through the siding (forcing the finish off in the process).

- Rich

[MarkMc]

Mark,

Thanks for that. That's the type of reasoning I was looking for. So does felt really stop the capillary action more than the gaps created by lapping the siding??

Depends. No absolute answer w/o an absolute question. Don't mean to sound flip but... it's awesome when you think about how liquids get from below the ground around the base of a redwood, or saguaro for that matter, all the way up to the top.

Don't forget the rest, adhesion and cohesion, the joys of vapor[s], that the 'little straws' in wood don't all start/stop at the ends. Can felt serve to break that action, yes, so can tyvek or a sheet of metal. Can nails, staples, outbound vapor punch holes in our plans... Once had a FPL fella tell me, 'just put the [wood] siding on a suitable angle so it can drain, then put gutters at both ends.' ;

[Alaskan Son]

So what do you guys think about the use of T1-11 over bare studs??

[Dick Seibert]

So what do you guys think about the use of T1-11 over bare studs??

Believe it or not when T1-11 first came out in the 50s it was made in 3/8" and 5/8" versions, the manufacturers obtained an ICBO Report approving it without a WRB, the only requirements were 2" strips of asphalt felt under all vertical seams and Z metal at horizontal seams. I worked as a carpenter for a cheap company and built a few additions that way, I never have heard how it worked out.

[Allan Edwards]

Believe it or not when T1-11 first came out in the 50s it was made in 3/8" and 5/8" versions, the manufacturers obtained an ICBO Report approving it without a WRB, the only requirements were 2" strips of asphalt felt under all vertical seams and Z metal at horizontal seams. I worked as a carpenter for a cheap company and built a few additions that way, I never have heard how it worked out.

I wasn't building in the 50's but I do remember the 2" strips of felt only on studs, and the Z metal at seams.

[Alaskan Son]

I wasn't building in the 50's but I do remember the 2" strips of felt only on studs, and the Z metal at seams.

Around here this is still standard practice only without the felt strips. Probably over half the siding on new homes is T1-11 or smart side T1-11 over bare studs. Have yet to see any adverse effects except once when there was housewrap underneath it.

The majority of any moisture problems I've ever run into on houses built like this are due to poor window and door details. And I'm not talking extravagant flashing. Just a lack of caulking on the top trim piece, or a lack of any kind of caulking or sill pan at the bottom of exterior doors.

Any other moisture problems are usually if not always caused by air leaks on the leeward side of the house, or from condensation due to a lack of vapor barrier. The housewraps seem to only exacerbate these problem areas.

This was the reason for my original question. If the only reason for felt behind cedar is for a WRB, and if I am seeing more negative than positive effects from the WRB, it seems only logical to question whether or not its really a good idea everywhere. From what I've seen, if you're using your average modern building methods in climates such as mine...either housewrap with furring strips (and even this I question a little), or no housewrap at all. As I said before I have yet to see any problems caused by felt, by then again I have never taken apart a modern house built with felt. Can't imagine it performs all that much differently than housewrap though.

Thanks for all the input guys.