My home has painted t111 cedar siding over probably 15 lb felt and 5/8′ plywood. I am thinking of adding cement lap siding to all of this existing siding and was curious what everyones thought were about using a housewrap first. My inclination is that it would not be helpful at this point and could even have a downside here in our sometimes wet Western Oregon.
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Dave Graf
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it is hard to see what you would gain by it.
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No need for it , you won't gain anything .
It would be worthwhile if wind infiltration were a significant problem, but I gather that's not as big a deal there as here. But it's something you may want to evaluate for your specific house -- if you notice drafts on windy days then the housewrap may be justified.
If you pull the corner trim and any trim currently covering joints from the T111 so the hardi siding can be nailed flat, what is protecting your corners as a backup to caulk other than "maybe" felt under all that mess?
Since hardi (or other) is most often butted to the corner and window trim, I'd want the protection provided by house wrap or another layer of 15 lb felt, especially at corners.
I have little faith in old building felt installed by others, burried under old T111. Same for old flashing. We'd get laughed out of town trying to use the excuse that the original felt "should have been installed correctly."
Beer was created so carpenters wouldn't rule the world.
I had thought about the corners too, but my concern is that having the T111 sandwiched between the housewrap and the old felt is in itself a problem. Any moisture caught in between these layers could be a problem and a nice place for mold to grow. I would agree that the old felt is permeable to a point, but is it enough to let any trapped moisture escape? I think my inclination would be to felt the corners and call it good.
Wind isn't a big problem in terms of infiltration, these walls are still tight and the existing paint is OK. There are some areas on the South side where the cedar is showing the signs of age, hence the interest in new siding.
Dave Graf
Housewrap is vapor-permeable.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
My neighbor is doing exactly that. Cement board over T111. He is putting down 15 # felt over the T111. for the corners he added some 1x cedar to stand proud of the cement board. You will be pleased with the new look. By the way this is in Newport Or.
You may have no sheathing under that t1-11 not that it matters but make sure you nail your siding to the studs.
All trade, You are correct in what you say. I will add that there may be no felt paper under the original T-111. I remember when some builders would omit the felt paper because the glue line was considered "water proof". It passed inspections here in Oregon for years that way . I still wouldn't add felt though , except a 12" wide strip at the corners.
The only reason i would forget the paper is if the t1-11 was painted or stained well. Acually some paints are considerd vapor barriers so dealing with that issue is a must.
AllTrade,
PVA primer passes the Perm requirements as a vapor barrier.
Do you really have plywood under the T1-11?......'round here T1-11 goes right onto the studs and that's your finish surface....are there corner boards applied over the T1-11 or does the T1-11 butt to the corners and trim?
Geoff
Yes, amazingly enough there is a 5/8" plywood layer under the T111. The aluminum window flanges were attached to that layer, then the felt tarpaper and the T111. The T111 was butted tight to the window frames without any trim. A very basic way of doing things. So there is much we can do to improve the appearance. We just added all new windows and I'm trimming them in now both outside and then inside. Dave Graf
Dave, you didn't say whether or not there are corner boards,....
You say you have already replaced the windows, so I'm assuming you cut back the T1-11 to accommodate the new windows install flanges........
Is it possible to remove all the T1-11 then install your home slicker/felt paper/house wrap?......seems that would make everything a lot easier for trim and siding install..... and no worries about moisture behind the double layer of sheathing........maybe worth considering??
Geoff
There are existing 3/4" x 4" corner boards. When we replaced the windows I allowed our installer to simply cut the old aluminum flange and leave it in place. Then installed the new window flange to the surface of the T111. I know many would have cut the T111 back exposing the old flange, but I'm not a fan of doing more work than is really necessary. I'm very confident of the new exterior seal and will do even more work on the interior side, then as I add the 5/4" trim around the window frames I will again add more sealant. As for removing the existing T111, I don't see the point. It is there, it isn't hurting anything, it is just a little plain for my tastes. When we add the Hardi plank I will also replace the corner boards with the 5/4 trim and think that should work pretty well.Dave Graf