Silicone Chimney Flashing

[Craig56]

I'm building a cabin, have a 8/12 pitch metal roof with ridges in it. I was looking at flashing in a local stove store and they recommend a silicon flashing with and aluminum flange built into the outer edge. I was wondering if anyone has used one, or has any comments on these?

Craig

 

[SteveKG]

I installed one about three months back, so my experience is limited to installing it. Too soon to say how it will hold up.

It was simple to install. The one I bought had to be trimmed to size for the pipe. It also needed to be sealed down to the roof [metal roofing in my case] and I used butyl tape and then butyl sealant around the perimeter after I screwed it down.

 

[Craig56]

Thanks Steve, I'm going to order one online, the one they have localy has a round base, the one online has a square base, thought I'd go with the square, plus they have it for about $30 cheaper online. Sealing it in the winter should be fun. I was thinking I'd take on old heating blanket up there and wrap the base of the chimney pipe anf roof with it for a while then put down the silicone and when done wrap the pipe/flashing back up in the heating blanket for the rest of the day to get the silicone to cure a little before exposing it to the cold temps at 8200', unless someone has a better idea.

Craig

 

[SteveKG]

Thanks Steve, I'm going to order one online, the one they have localy has a round base, the one online has a square base, thought I'd go with the square, plus they have it for about $30 cheaper online. Sealing it in the winter should be fun. I was thinking I'd take on old heating blanket up there and wrap the base of the chimney pipe anf roof with it for a while then put down the silicone and when done wrap the pipe/flashing back up in the heating blanket for the rest of the day to get the silicone to cure a little before exposing it to the cold temps at 8200', unless someone has a better idea.

Craig

I bought the square one, too. If yours is the type you cut to size [of pipe], be careful not to cut too much. Cut it slightly smaller than you think, then trim off a quarter inch or so at a time. You want a fairly snug fit on the pipe. I used a box cutter with a brand-new blade and it worked well. Go slowly.

The instructions with mine said to use self-tapping screws to secure it down to the roof. No way. I had to predrill holes in the aluminum strips at the perimeter, and down through the metal roofing, then install the screws. My boot arrived "folded up" in a padded bag, so the aluminum strips were bent up and I had to carefully straighten them out first. It wasn't a big deal, just another little chore to do before installation.

I had a standing seam in the way, just how the location of the pipe worked out. I cut the standing seam [talking about on the steel roofing] back a few inches from the area where I wanted to seal down the boot. My roof was so steep I couldn't get the boot to lay down flat enough as the seam was in the way. I used a pair of metal snips after I had cut through the seam with a Sawzall, but it could be done easily enough with a hacksaw. If you don't have a seam in the way, lucky you.

I sealed around the top of the silicone against the chimney pipe, then to be extra sure I bought and put on one of those "rain collars" that fit around the pipe to deflect rain out a few inches from the pipe and that collar is just above the top of the silicone boot.

That's just me.

 

[Craig56]

I have self starting screws left over from my roof, they went in pretty easily in the roof, so I may predrill the flange just to make it easier, but I think they'll go in ok. I did buy the biggest one I could 7"-11", hope to make the angle a little easier when I put the flange to the roof. You definitely need the rain collar.

Craig