Thread: Roof mastic around flue

I have never seen the heat tape before, but do you call out excessive use of mastic and or sealant around stacks and flues?

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Pic 1) Opinion not fact; heat tape there as a creative resolution to problem of ice build up creating a ice dam resulting in leakage.
Pic 2) Needs excessive caulk/sealant to prevent water that will be dammed up by penetration. I would make point to stress need to inspect often and maintain seal to prevent leakage. Not a metal roofer so not sure if there is a way to create a saddle of some kind that would allow water to not be restricted as it is at present. Having a metal roof contractor inspect and provide resolution. Excess sealant is first method to stave off the inevitable leak if not maintained.

Matt, looks like you've taken a recent trip to Philly based on those pics .

Both chimneys are wrong. Any amount of mastic/roofing tar is combustible and so is the rubber gasket boot in the 2nd pic (at least it appears to be a rubber gasket boot). Both are combustible materials and should not be in contact with the flue pipes.

Both the rings of insulative/thermal buffering materials in direct contact with the B or L venting as well as (egad!) the operation of said "heat tape" encirciling the vent penetration can and will NEGATIVELY EFFECT the ability of the gravity draft mechanism within the vent assembly itself. It is not a proper "priming" mechanism for such venting in conditions where frosting or freezing in the area of the penetration might occur, and likely would cause spillage into the home. Should less than complete combustion having taken place, this could include CO, excess CO2, and unspent fuel.

Furthermore, the presence of both/either can and likely will cause expidited deterioration of the venting equipment. ("hot spot/ring deterioration, condensation, corrosive processes of unvented products of combustion, etc.).

Finally, IMO, the heat tape by itself in such a location is just plain dangerously stupid. Contact between disimilar metal of the weathered "heat tape" exposed conductor to the vent can accelerate corrosion. Should the conductor be energized, a dangerous objectional current upon the venting material and whatever is in contact with same may result. The exposed "heat tape" if connected electrically could act as a pathway for other sources of objectional current (i.e. other equipment "leakage", arcs - lightening, etc.). Should unspent fuel escape it could (objectional current) serve to ignite such vapors. If the area was frozen, it would soon warm due to natural result of the vent having been slowly primed and actively drafting the products of combustion. The heat cable in such a position would thusly just increase the likelihood of melting and with a frozen surrounding area, promote drainage through the very area the poorly and ignornatly instilled "tar goop" has been piled, and apparent leak zone. Such would therefore be expected BELOW (i.e. following the slope of the roof to a lower elevation) so as to promote drainage. If the exhaust vent is subject to being submerged or smothered in snowfall, or ice accumulations then the exhaust venting system should be redesigned.

There are appropriate offsets to penetrations, cowls and boots used. Clearances from the mfg. and code must be maintained.

I just put in the report, she is a beaut

If you cut in a proper curb and chase, the roofer and properly seal these up then you can install a chase top as used on most factory built fireplaces and be done with it. No need for heat tape.

Any joint that relies solely on goop (spelled 'caulk') can and will eventually fail to water penetration.

I would be more concerned with electricity outdoors exposed. BTW, is that outdoor rated heat tape? Are there any combustibles anywhere near this heat tape?

What is that first termination with the fine mesh? Looks like a problem. Would need to identify as a listed component.
Bob

{slaps self on head} Fireplaces, Chimneys and Solid fuel appliances section.

Forgive pontificating with terms like B vent and L vent please. (chalk - not caulk - it up to senior moments and failure to expand thumbnail photos or knowing where I was. ).

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