Thread: Storm collars and fireplace flues, with mastic

Ok I just put a post on here but Im putting another. I see this every day on every home, its the standard here. Is this incorrect, are all of these wrong. And how do you tell if its roof mastic or an approved sealant, is there a method. I really got into with a guy today. Oh... is mastic fire rated.

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There are class A rated mastic, the worse problem I see are vertical structures next to the caps, there are clearance requirements.

The mfr will state the minimum size hole in the chase cover for that system. If you make the collar too tight or caulk it shut, you trap heat in the chase, which, as Dale Feb can attest, is a leading cause of fires. These chases must breathe. If the chase cover is properly made and pitched, there should not be standing water at this collar. While we try to use covers with pre-punched or swaged collar made by stretching the metal seamlessly, you can do a cut-in collar. We will often make these up on site using a simple sheetmetal sleeve and notchers. The tabs are bent over the underside of the hole with a few left on top to screw into the chase top. This joint is them caulked with silicone, neoprene (Black Jack), or typical plastic roof cement. Then the mfrs. listed storm collar is attached directly to the chimney or vent using the sealant approved by the mfr. (usually 300F* rated) ensuring the gap at the collar so the chase breathes. The termination must extend a specified distance above the chase top and some of these appear too short. If the cap is so low the collar blocks the cooling air, you could cause a fire down below. I'm sure that shroud in the photo is not listed for use with all three of those chimneys & vents and therefore is a fire hazard. Also note that whether a direct vent gas termination or an air cooled woodburner chimney, shrouds can trap exhaust gases allowing them to recirculate down the other vent's concentric space back into the home. I've seen gas and wood units where their chimney/ vent rotted out for several few down due to proximity to an oil fired unit's chimney that was too short and too close or in a shroud.

HTH,

Thanks

Bob I can see your eyes bugging out of you head now But 95 percent of the homes in the hood have these. The houses are massive so if they do go up it should be quite a seen

Spelled "job security" for Dale Feb....