Installing Stovepipe through Living Roof Membrane

by ziggy on October 7, 2010 -- 1 comment -- Follow

Test firing the Morso 1410

It’s done! We’ve got a fully functioning woodstove, with the stovepipe penetrating the living roof of the house, all sealed up and complete. So how did we do it? How did we send a stovepipe through the EPDM liner of our living roof?

As I described in part one of installing stovepipe for the Morso 1410, we tore a hole through the cob wall above the stove into the mudroom. The next step was removing the soil on the rooftop to prepare for busting through the EPDM pond liner.

Removing the soil

I started at the edge of the roof, and using my hands (I used no tools for fear of puncturing the liner), ripped up the sod and pushed it down off the roof and onto the ground below. I worked my way up to where I thought the pipe would exit the roof, and then had a helper go inside to knock on the decking board below that would eventually be removed. Listening closely for the sound, I got a good idea of where the pipe would eventually be, and pulled up enough soil around that area.

With the soil now removed, I decided to use two long 2x4s to slip underneath the pond liner up to the (future) exit hole, to get the liner raised up and further away from the saw blade that we would use to tear up the decking board.

Sawing through the decking boards

Next I ran and borrowed a sawzall, and we sawed a decking board in half from inside the mudroom, and pulled it out to make space for the future double wall pipe. That was actually easier than the next step, which involved cutting through multiple layers of cardboard to get through to the EPDM. It was difficult to do this part neatly.

View from below of pipe exiting wall, EPDM exposed and ready to be cut

Cutting a hole in the EPDM

Now for the most hyped up step of the process… cutting the hole in the EPDM. It was actually the simplest part of this entire process. I traced a piece of pipe on a sheet of newspaper, and drew in a smaller circle (one inch smaller in diameter), cut out the circle, and brought it up to the roof. I traced this template on the EPDM and cut the hole. That was it.

Cutting the hole!

Next we realized that we needed more space for the double wall pipe than just removing the single decking board. We went back in with the sawzall and carved out the two neighboring decking boards a bit to allow more clearance space for the pipe.

Cutting out extra space for the double wall pipe

Creating a stovepipe support brace

Truly the trickiest part of this installation was now at hand: creating some kind of supportive brace for the stack. Here’s how it happened. The plan was to fit on an insulated tee joint onto the stovepipe exiting the wall. The double wall stack would attach to the tee, but the whole assembly would need some support from below, because otherwise the tee and double wall would be, well, floating there.

The tee joint had little area other than the rim of the clean-out hole for a bearing surface. I made a square (just big enough to be able to remove the tee cap) for the base of the brace. I can’t easily explain how I made the rest of the brace, but I did some fancy measurements and estimations and figured out where it would attach to the wall, and assembled the rest of the brace as I went. I attached it to the wall with some very nifty masonry expanding bolts. I drilled holes into the cob, tapped in the bolts, and as they were tightened, they expanded in the wall, keeping them locked in position, and the brace very steady.

stovepipe install 05

Stovepipe support assembly with tee joint

I sat the tee joint on top of the brace, and finally slid the double wall pipe from above onto the tee, and locked the two together. Viola! Now for sealing the hole tight.

Sealing the stovepipe

I carefully cleaned the EPDM around the pipe, which was difficult because dirt was constantly shaking loose from above the hole. Once it was satisfactory, though, I pulled up the EPDM around the pipe from above, and taped the pipe to the EPDM with Eternabond RoofSeal tape (of the 4″ wide variety). This tape is pretty intense stuff. It sticks to damn near everything. Once it’s on, it is on and not coming off. Normally this tape is used for sealing leaks and making repairs, but I figured it should be strong enough to make a seal. And I think it is. It’s intensely sticky.

Over the stovepipe I placed a special silicone rubber boot, which I found and purchased here. This particular item is the keystone to the entire installation through the living roof (combined with the Eternabond tape). This is what makes running the pipe through the roof even possible. This silicone flashing is heat resistant to some ridiculously high temperatures, and flexible, so it conforms to an irregular roof pitch and fits snugly around the pipe. I slid it over the pipe from above and down to the EPDM. Next I used the Eternabond tape to seal around the base of the boot to the roof.

Fully sealed stovepipe with rubber boot

Finally, I used silicone caulk around the top of the boot and then put a metal storm collar on and caulked that as well. Ultimately, there are three layers of protection against water getting through.

And that was it! (Whew.)

We’ve since fired the stove a half dozen times, and there have been no problems yet! It hasn’t actually rained since we installed the stovepipe, but I have no fear that the pipe will leak.

We’re ready for winter!

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  • Lisa Morales

    This really warms my heart! It looks like a great job and a toasty fire. God bless you all.

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