The Log house Project begins........

[dave1949]

As ENG18LT pointed out, my standing seam roof has Grace Ice&Water under it everywhere, not just the eaves. My roof is 5/8" Advantix sheathing on 16" OC trusses, then the Grace, then the metal. I don't have any problems with the roof, although it was expensive. The roofer told me he strongly recommended the complete Grace coverage, I have a better understanding now of why.

Rick, if you end up having to remove the tin, one option is to add a sheathing layer atop your existing purlins, but down Grace or similar, then the tin. You could add foam between the purlins too. That might be the more expensive route, but it seems like the surest route to success.

 

[MotorSeven]

I think stripping the tin and adding foam/or waterproofing on top of the purlins is a viable option. But before I take that on I think I will try the suggestions of a larger and better vented ridge cap. That's only a day project with a man lift and I can tackle it myself. If that does not solve the problem then like Dstg said it looks like a "spring project" is in order:muttering:

So I step out on the front porch this morning and see about a gallon of pooled water on the deck boards....."what the he..." Les looks out and goes, "I just watered the plants"ullinghair:

 

[EddieWalker]

Be careful that you are addressing the problem when you do your repair. Some of what I'm reading here is confusing and misleading. Both in the interpertation of what was done on their roof, and what they feel you should do to yours.

If you go for the waterproofing method under the metal, realize that you are not stopping the condensation. You are just cutting down on the amount of air under the metal and channeling the water the does form there down the bottom of the metal to your eaves. It is still there, just less of it. Plastic held suspended is also a very good way to create condensation. It's actually a survival method to get drinking water when lost in the woods. Foam is a very good solution to stop condensation. It's drawback is what it will cost you. Air flow is a time proven, low technology solution that is very effective.

R Panels are different then Standing Seam roofs. What is done for one is not done for the other. Before you do anything, you might want to go talk to your metal supplier. Bring pictures of what your roof is like before the metal went up and ask for solutions.

Eddie

 

[tnmike]

+1 on the ridge vent. Try the cheapest and easiest solution first.

 

[dave1949]

Be careful that you are addressing the problem when you do your repair. Some of what I'm reading here is confusing and misleading. Both in the interpertation of what was done on their roof, and what they feel you should do to yours.

If you go for the waterproofing method under the metal, realize that you are not stopping the condensation. You are just cutting down on the amount of air under the metal and channeling the water the does form there down the bottom of the metal to your eaves. It is still there, just less of it. Plastic held suspended is also a very good way to create condensation. It's actually a survival method to get drinking water when lost in the woods. Foam is a very good solution to stop condensation. It's drawback is what it will cost you. Air flow is a time proven, low technology solution that is very effective.

R Panels are different then Standing Seam roofs. What is done for one is not done for the other. Before you do anything, you might want to go talk to your metal supplier. Bring pictures of what your roof is like before the metal went up and ask for solutions.

Eddie

I see two problems facing Rick. One is there doesn't seem to be a corrective action that doesn't involve multiple vapor barrier layers, something that is not recommended. The second is I don't think the profile of his tin, given that the horizontal purlins are acting as air dams, is ever going to allow enough air flow to adequately function as a normal eave-to-ridge air circuit. Adding foil/foam (a second or third vapor barrier in Rick's case) to the underside of the tin or across the purlins, will reduce the possibility of air flow.

The eave-to-ridge approach assumes an attic, or at least the free space between vertical rafters that is kept open by trays at the eaves, in the case of a full cathedral ceiling. Rick doesn't have either of those.

I don't disagree about tried and true airflow, but none of the ideas so far will provide enough is what I am thinking. There either needs to be sufficient air flow, or eliminate the need for it.

 

[brin]

The second is I don't think the profile of his tin, given that the horizontal purlins are acting as air dams, is ever going to allow enough air flow to adequately function as a normal eave-to-ridge air circuit.

Dave....I agree, unfortunate the purlins are horizontal...otherwise there would have been a chance but even then it seems it would have depended on enough air circulating since there is not attic or means to have a solar or electric exhaust fan to create the air flow -- I hope Rick comes up with a fix short or tearing the tin off.

 

[Rock knocker]

I would council caution and patience in your remedy. While Grace sounds like a good idea, I would hate for the IWS to act as a vapor barrier and have condensate form in and on the underlying roof seathing, with the attendant dry rot occuring there. Same priciples would apply to any insulating foam. You need to keep the moisture on the warm side of the vapor barrier.

As was also stated, keep the internal humidity down. Do you actually have a ventless NG or LPG appliance?

Could you make a little drawing of your roof section for us?

 

[dave1949]

I would council caution and patience in your remedy. While Grace sounds like a good idea, I would hate for the IWS to act as a vapor barrier and have condensate form in and on the underlying roof seathing, with the attendant dry rot occuring there. Same priciples would apply to any insulating foam. You need to keep the moisture on the warm side of the vapor barrier.
<snip>

Yep, that is the problem with multiple vapor barriers. Moisture can get trapped between them and has no way of migrating out.

 

[pacerron]

Maybe this will help you guys that are stuck on ridge vents, Cupolas and other contraptions to fix the problem better understand Rick's roof sandwich.
I went back through his posts and found this picture he posted of the roof sandwich under construction. His description is partially captioned under the picture.
I hope you see that any ridge venting will only occur in the area above the top purlin that he has his foot on and the ridge.
Since the bottom of the roof tin is elevated 1.5 inches above the 3" foam insulation layer the sweat that occurs under the tin can only fall to the 3" styrofoam
and accumulate where the edge of the purlin meets the foam until it finds a place to leak out, evaporate, or make a sick moldy mess on the foam that could become a health hazard.
Ron

 

[pacerron]

Here is a picture showing the 1st and second layer of his sandwich.
I could not tell from the post picture above if the styrofoam was foil coated or open cell?