Cold Temps and Flashing Installation
when is it too cold to flash & roof (eg installing ‘long’ exterior products in winter)
I have a ~”tiny house” that needs it’s roof finished. I got the underlayment down (all ice-dam, given it’s size) but am now into pretty cold weather. I’d strongly prefer to finish it rather than temporarily cover (ice-dam is only rated for 90 days exposure), but am worried I’ll have a huge problem with expansion come summer. Our temperature here falls well below zero (F) on a number of days in the winter, as well as above 100F in the summer.
What ballpark temp is cold enough that I temp obvious thermal-induced warping in the summer, for the ~long exterior materials, namely 10-20ft metal flashing, and 12ft long metal roof sections? The roof of this is quite small, 16ft x 10ft, but the products themselves are identical with a full house.
I’d like to finish the roof on one of the weekends sunny enough I can fully clear the roof of snow/moisture, but am concerned I’ll regret this come summer!!
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Replies
You always want to install flashing so it can move. The way to do this is to pin it in the middle and drill 1/4" holes at the rest of the locations to allow for a bit of float. Snap lock panels have slotted holes specifically to allow for thermal expansion.
You definitely can run into buckling when installing in the cold if not careful, so waiting might be the best. It is no fun to handle metal in the cold, I would wait for a nice sunny spring day and finish the roof.
That 90 days for the peel and stick can be stretched, I have done much longer than that and held up fine (there is a house near me that has had a peel and stick porch roof that is about 3 years old now).
Thanks for your reply. I'm right on board with you with what an ideal flashing design should be (located only a single time in long axis, rest has play) - and at my roof's scale i could definitely prefab those holes on the ground.
I does make me wonder, though: does _anyone_ do this on the clock? If i use standing seam (other option is corrugated), that will come with long-axis expansion inherent in the design. But i have never personally seen or heard of flashing performed with any physical modification like this (but my sample size is just several houses we've done along with friends' place - ie low).
Is this done in the trades? Or just install in as mild as mild weather as job schedule allows, and hope for no callbacks?
Trim problems are real. There many expensive renos I have seen with buckled trim. Since these tend to be way up high, nobody really looks too closely. Lot of this work also rarely happens in the cold weather, installing when hot is not an issue as the trim will easily pull the fasteners out a bit when it shrinks in the winter.
There were posts on this site with people having this issue once the temperature warmed up.
As with anything, easier to do it right the first time then to fix it down the road.
It is very hard to buckle corrugated, so I wouldn't worry about that. For me snap lock VS corrugated is maintaince. Each one of those screws on a corrugated roof is a potential leak point, not something I care to deal with down the road.
neutral_grey,
The only way I could imagine doing that is to use cleats, and it would be very complicated. Have I ever seen anyone do it? No.
Roof boots, gable and end-wall, and ridge trim - an awful lot of the flashing is secured by gasketted fasteners to an un-moving substrate, and they can't be used in slotted holes.
Maybe it's because unlike Akos I build in a temperate climate without huge seasonal swings, but I've never had any problem with the trim I secure directly through the material. Even the slots on roof panels don't line up when you use strapping.