Johanne from Laval, Quebec writes: "Could it be damaging to my new shingle roof to climb up on it in the winter time to install a satellite antenna? If so, what would be the ideal temperature to do work without any damage?"
Aside from slipping on ice, winter is not a bad time to walk on that roof but not the best time.
To illustrate the problem we took three pieces of asphalt shingle and plunged one into a cooler full of ice, left one at roof temperature and put the third under a heat lamp. Then we manipulated each of them to check out two things: what happens if you bend the shingle, and how easy is it to scrape the protective grains off the surface?
A cold shingle is quite brittle. If you must lift a corner, do it ever so gently as while it is cold it can simply snap off. The room temperature shingle has a reasonable flexibility but you can go too far and fracture the fibre even though you may not snap it off, permanently weakening it. When it is truly hot, asphalt shingle are extremely flexible and you can manipulate them safely.
On the other hand, the warmer and more flexible the shingle, the easier it is to scrape off the granules as you walk around.
Moral? Mostly walking over the shingles -- do it while they are colder. Manipulating the shingles themselves, do it when it is warmer. Click here for more information on asphalt shingles and the weather.