I have a home built in 1795. Thirteen years go I had all new cedar clapboard installed and the trim replaced. The builder put up to 1 1/2 foil faced Tuff R foam insulation on top of the old siding, then put 1/2 plwood sheathing, and then put Tyvek over the plywood, followed by the cedar clapboards and trim.
The cedar was stained white about six times over 8 years. About 5 years ago, it was painted with Permawhite mildew resistant paint. On the east side of the house, that gets heavy morning sun, the paint is now badly peeling.
Before I painted again, I decided to investigate a little further. I took off the water table trim (the wide board at the bottom of the clapboards) that was peeling the worst, and it was partially wet and rotted. What is puzzling to me is that the outside of the tyvek, and the underside of the clapboards were nice and dry, but in some places (not all) underneath the Tyvek the plywood sheathing was wet, not rotted, but damp. To be clear, the exterior side of the Tyvek was dry, but when you lifted it up, the sheathing it was covering was wet and damp in some places.
I don’t have any interior problems, and I don’t understand how interior moisture vapor could get through the foil faced Tuff R. I also thought tyvek would breathe and dry out, instead of capturing moisture underneath.
If anyone has a clue to what might be happening I’d appreciate hearing from you. Thanks!
Replies
sounds like he did about everything right... now if he'd just fir'd it out and left an air gap behind the siding you'd be all good... not sure there is an easy fix... but someone here will tell u... does sound like your house is alot thicker now... that extra 3/4" might have caused problems they didn't want to deal with... but even 1/4" is better than zero...
pony
First off........welcome to BT.
Since you haven't yet filled in any profile info on yourself, would you tell us where you're located? Geographical location/ climatic conditions may play a role here.
Do you normally/frequently have heavy dew on the outside of the house in the morning?
Thanks for the welcome and reply, and I missed the profile part.The house is in Middlefield, CT, on a hill where it is always fairly breezy, with the breeze coming out of the valley. Yes, there is heavy dew on the house in the morning. I would say unusually so. The sides with the worst problem are the east, southeast. The north and west sides are not as bad.
As to a little profile info (for future reference when you post), just click on your name at the top of a post and then click on "change profile". You can then add info.SWAG on your problem.........The condensation on the exterior of the house is being heated by the morning sun and a portion of that is driven inward under the siding and thru the Tyvek (cause it allows for vapor passage). Once the sun swings past the east side of the house, this vapor is condensing back there. More collects back there than frequently has opportunity to completely dissipate before evening falls and the cycle begins again. The whole process keeps the siding a bit damp and that's the cause of the paint failure. The siding may feel dry to your hand, but if you stick the pins of a moisture meter in it, you'll likely discover otherwise.I suspect your water table is damp and rotted from the condensed moisture behind the siding forming trickles and gravity then takes that to the water table. East and north sides of houses are normally the ones prone to accumulated moisture problems around these parts and I doubt it's much different where you live.You're not going to prevent the condensation from forming on the siding during the night, so it would seem that more ventilation under/behind that siding to allow it to dissipate is where the cure would lie. Knowledge is power, but only if applied in a timely fashion.
Am I making this up or do I remember hearing about some kind of spacers/wedges that are used in case like this to hold the bottom of the clapboards out a hair so that they can dry from behind.
You're not imagining. 1/8" thick plastic wedges are availble for this. But......I don't care for the resulting look myself. If possible, I'd sooner install the siding over over some 3/4" furring strips (with outlet venting at top of wall too, of course). Bottom and top should be screened to prevent insect intrusion.Knowledge is power, but only if applied in a timely fashion.
Edited 4/17/2005 2:39 pm ET by GOLDHILLER
Thanks for all the good thoughts.This sounds like a very plausible explanation. Seems to coincide with the condition of the siding nails. The first exterior (head) 3/8 th of the nail are rusting and corroding.From your explanation, and what the other replies seem to indicate, an airspace sounds like the solution, which means re-siding the house. Ugh. If I reside with something like Hardiplank, with an airspace, would that be preferable? Is vinyl (although not appropriate for my house given its history) not subject to the same problem because moisture can't reverse itself though the plastic?
Hardi will outlast the cedar and hold paint better, but it's thin and doesn't create as pleasing a shadowline that real wood claps do. As long as your current siding isn't rotted from the moisture, then I would reuse it. Be sure to prime all sides, however, not just the face - that adds a lot of protection when moisture gets behind the siding.
As an alternative to firing out the siding further (which may mess up your trim), you can use a nylon mesh product designed for rain screen applications. A popular one is here: http://www.benjaminobdyke.com/html/products/slicker.html
The nice thing about them is they are thinner than fir strips, which may save extensive work on window and door trim.
For a good article on what your house is probably experiencing and the solution people have described in this post, read this:
http://www.taunton.com/finehomebuilding/pages/h00150.asp
Good luck!
Thanks Andy. I have read about the Obdyke product, but wasn't sure if it worked. I have also seen the Tyvey with the ripples that is supposed to do a similar job. At this point, I need to find the best long lasting solution. I can't tell my wife 13 years from now that I screwed up again!