Leaking metal roofing
#1
08-25-21, 05:51 PM
Leaking metal roofing
I had solar installed on my metal roof approximately 6 years ago. It was suggested to me to coat the roof with an acrilyc coating prior to the installation of the solar panels as a precautionary method. The premise was that you dont want to have to remove or mess with the panels later if you should get a leak. Now note my roof is old but it was damage/ rust free throughout most of the roof. The recommendation sounded right and it was costly but I opted to get it done. Now about a little less than 10 years later and still under the white coating warranty, I have rust coming out from everywhere. The licensed contractor that did the job said that there labor warranty is up and they wanted 30,000 to do it again. The rep said "well mate, iv'e seen worst. What gets me is that were its rusting through, it appears to start from the edges of the fabric that they put on and not from a protrusion. I have contacted several other roofing contractors and asked them about the rust.They all know who the local rep is and when they know that its still covered, they start to
backpeddle and make broad assumptions on why its rusting. I know that i didnt type in the whole story with more facts but this ipad is somewhat small for my fingers and eyes. Anyway, anyone with questions or advice? Going to try and figure out how to send pics for everyone to see.
backpeddle and make broad assumptions on why its rusting. I know that i didnt type in the whole story with more facts but this ipad is somewhat small for my fingers and eyes. Anyway, anyone with questions or advice? Going to try and figure out how to send pics for everyone to see.
#3
08-25-21, 07:53 PM
Group Moderator
Well, a couple things. I'm not a commercial roofer but I have been around the block enough to theorize what's going on there.
Metal roofs should almost always have a high temp ice and water shield underlayment applied to the entire roof deck BEFORE the metal roofing goes on. This does a couple things. It's a vapor barrier so that you don't get moisture from inside collecting on the metal and causing condensation under/against the roofing. And secondly, if there are any leaks from above, it ensures that water drains harmlessly out the bottom, rather than leaking inside and running framing, sheathing, insulation, drywall, etc.
If this is a pole barn type roof, where the metal roofing is applied over purlins with an air space underneath and no sheathing, that complicates things. Roofs like that weren't usually built to be heated in winter, and adding heat causes moisture problems in winter.
Without knowing what's under your roof, I can only theorize that you have no vapor barrier, and that moisture is trying to migrate out, it hits a cold surface, and condenses. So the metal is wet when the conditions are right for it... winter, early spring, late fall. If this is only happening at the seams of their fabric, then that might be where inside condensation is able to migrate under the metal roofing near the seam. Then it's trapped and can't dry out, so the moisture is rusting the metal.
It would be interesting to know how far their "fabric" is supposed to be lapped, and how that seam is sealed. And if that was done according to mfg's instructions.
Also no info on how the building is used, whether it's insulated at all... or whether it is heated in winter, or just occasionally... or what kind of heat is being used. These are all factors.
One possible solution might be to spray foam the bottom of the roof deck with several inches of insulation to prevent that moisture from coming into contact with a cold surface.
Metal roofs should almost always have a high temp ice and water shield underlayment applied to the entire roof deck BEFORE the metal roofing goes on. This does a couple things. It's a vapor barrier so that you don't get moisture from inside collecting on the metal and causing condensation under/against the roofing. And secondly, if there are any leaks from above, it ensures that water drains harmlessly out the bottom, rather than leaking inside and running framing, sheathing, insulation, drywall, etc.
If this is a pole barn type roof, where the metal roofing is applied over purlins with an air space underneath and no sheathing, that complicates things. Roofs like that weren't usually built to be heated in winter, and adding heat causes moisture problems in winter.
Without knowing what's under your roof, I can only theorize that you have no vapor barrier, and that moisture is trying to migrate out, it hits a cold surface, and condenses. So the metal is wet when the conditions are right for it... winter, early spring, late fall. If this is only happening at the seams of their fabric, then that might be where inside condensation is able to migrate under the metal roofing near the seam. Then it's trapped and can't dry out, so the moisture is rusting the metal.
It would be interesting to know how far their "fabric" is supposed to be lapped, and how that seam is sealed. And if that was done according to mfg's instructions.
Also no info on how the building is used, whether it's insulated at all... or whether it is heated in winter, or just occasionally... or what kind of heat is being used. These are all factors.
One possible solution might be to spray foam the bottom of the roof deck with several inches of insulation to prevent that moisture from coming into contact with a cold surface.
#4
08-26-21, 02:05 AM
I would assume they used an elastomeric roof coating.They do a good job but shouldn't be applied over rust as they basically have no rust inhibitive properties. I also suspect purlins as the worst of it seems to be in a straight line. I'm not a roofer either although I've painted my share of them and that's what is on my house, barn and out bldgs.
For a quick easy fix I would caulk or tar any holes, prime the rusty areas with an exterior oil base primer and repaint as needed.
For a quick easy fix I would caulk or tar any holes, prime the rusty areas with an exterior oil base primer and repaint as needed.
#5
08-26-21, 09:50 AM
Im in the tropics. It doesn't snow here. The underside of my roof is bare with the purlins exposed. It was fine untill
the coating went on. Now I have rust coming out of the top even on the flat solid pieces of metal thaqt has no
protrusions whatsoever. Screws, overlaps, etc. To me the moisture gets traped under the edge of the round fiber cover that they installed over the screws and starts rusting which you can see in the picture.
the coating went on. Now I have rust coming out of the top even on the flat solid pieces of metal thaqt has no
protrusions whatsoever. Screws, overlaps, etc. To me the moisture gets traped under the edge of the round fiber cover that they installed over the screws and starts rusting which you can see in the picture.
