Looking to seal a gap between my furnace's vent pipe & the flashing on the roof, specifically here:


I'll have to check if there's a missing storm collar too, but should I use High-temp silicone, or go with the Big Box's recommendation of roofing asphalt (sounds burny).

1 Answer 1


I'd recommend Not using any petroleum-based sealant on any surface subject to heat (it will soften and melt). For a positive and weatherproof seal use any 100% silicone caulking (Dap, Owen-Corning, etc.). For an even better and longer lasting seal against water go with any exterior Urethane caulking. Well worth the slight cost increase, but is U.V resistant and stays pliable indefinetly. And there is no need for a high temperature rated sealer. Unless the area you are sealing is in close proximity to the heat source. Than you will need some type of refractory-type caulking.

  • Roofing company came out and said the same thing (their minimum was $275 unfortunately), so went with the silicone route. At least they gave the rest of the pipe/storm collar/rainguard an inspection too.
    – Alex Moore
    Aug 21, 2015 at 18:57

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