What to do About a Leaking Cupola
Hansen Pole Buildings has always used prefabricated cupolas manufactured by MWI – I even have one on top of my own house, so they must be good stuff! Only once have I ever gotten feedback from a client to tell me their cupola was leaking. In their particular case, it was because their builder had installed the cupola and its flashing first directly on top of the roof purlins. The builder had then butted the steel roofing and the ridge cap up against the cupola!
I know, it sounds counter intuitive and it was. Most of the time the Law of Gravity says, “water runs down hill”.
One of my readers recently wrote to tell me the cupola on the roof of his Cleary Building leaks every time it rains and he was looking for a fix.
Here was my advice:
Now I am not your average pole barn owner – and I don’t like exposed caulking. I’d be replacing what is there with a brand new cupola with a universal base. Besides what comes with the cupola kit, you would need a hand full of stitch screws the color of the base and two outside closures to put beneath the downhill edges of the base. Yes, it is going to be an investment, however it will solve the problem and look nice and new.
Assuming you want to fix what is there, here is the mission – find where it is leaking. Requires a hose and someone to stand inside and tell you when the water starts coming through. Begin with the flashings on the downhill edges, run a pretty good stream of water onto them (one at a time) for a minute or so. Even if the leak is along one of them, keep checking along the way, as it could be multiple points. Next do the flashing on the ridge cap sides. Then each side of the cupola individually (letting the water run down from the cupola roof).
If there is a leak, it should have shown up in the hose test. With the leak isolated, you can do a repair with the best silicone caulking money can buy. If one of the edges of the flashing is not sealed to the roof, Emseal AST expanding closures work quite well to fill those gaps. https://www.hansenpolebuildings.com/2016/03/emseal-self-expanding-sealant-tape-closures/