It is a flat roof and no heat. The roof will just extend over the end of the garage by 6 inches or so so the capillary effects shouldn’t prove hazardious. The profile is sort of |_____/ where you screw gets covered by a /\ shape. Would you suggest Nails or Screws to fasten it? I can’t see the thermal expansion being too strong, just as your cars hood doesn’t buckle in winter. Still looking into it a little but I think we are pretty set on getting it. Thanks for the advice guys!