We have some carports here that were installed by a previous owner a few years ago. They have side walls, but are open front and back, and have a steel box profile roof. Big green sheets like this:
https://www.roofingsheetsbyrhino.com/box-profile-roofing-sheets/
The sheets have an anti-condensation coating on them, which probably does the job it's supposed to… but sadly wicks water from on top of the sheets all over the underside. I initially naively thought it was coming up from the drip edge, so I scored the coating and tore a 4" strip of it off all along that edge.
That has helped, but I can see now that it's also problematic wherever the sheets overlap, especially on the end laps. I think the coating should have been stripped off the sheets wherever there's an overlap, and some lapping tape put in there, but as far as I can tell they did neither thing.
I'm not sure how best to solve this.
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take all the sheets off, trim the coating, add lapping tape, and re-fit… 😐
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seal the laps from above with some flashing tape or similar. The roofs are very visible from further up the garden and the house, so I'd want some tape the same colour as the sheets which feels like a big ask!
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other….? Any ideas?
Thank you!
Best Answer
And that's pretty typical of all steel roofs, and yours is the reason why.
The only way you can make a steel roof work on installations like this is if one piece of metal can span the entire roof. Not half to a peak. (because you can't make the peak seam work either, same reason). You can't have seams.
The simple fact is, you have a flat roof. 1-3 degrees is pretty much the minimum slope required to keep a flat roof from becoming a swimming pool, and is required by most roofing systems. You need to use products appropriate to flat roofs, such as EPDM rubber.