Fireplace chase construction

I am building the chase for my new fireplace on my new home and have a question. This is a pre-fab fireplace with the metal flue pipe. I understand when the pipe passes through the ceiling into the attic I need a fireplace spacer, but what about when it passes through the attic roof and into the chase on top of the roof? Do I just cut a round circle in the roof sheathing for it to pass through? Do I need any type of metal spacer when going through plywood into a chase on the roof?

 

Not sure what your local codes are. When I installed a freestanding Franklin stove in Ohio a number of years back, the stovepipe was single until it went through the ceiling. Then there was a metal adapter that changed the pipe to triple wall stainless steel pipe. This pipe went all the way through the roof. Although it was not stated in the code, I left about an inch all the way around the pipe exiting the roof.(made it easier for me to hit the hole) Then, the roof flashing kept it lined up and supported. I had to go 3 foot above the highest point of the roof to assure proper drafting and avoid downdrafts.

 

I was told to just follow the manufacturers instructions which state that I had to use their pipe. Its 2 wall pipe all the way to the top. It says to go atleast 2' above the peak of the roof so thats what I'm doing. So you just cut a circle in the roof sheathing and left about a 1" air gap between the pipe and the sheathing? There is no need to seal that or anything?

 

The roof flashing covered the opening around the pipe and sealed against the pipe about 4 or 5" up from the roof. The flashing was from the same company as the pipe so it was a snug fit and it had a clamp that held it tight to the pipe. I also purchased a spark arrestor cap for the pipe.

 

I replaced a fireplace some years ago, took me forever. I remember that I depended heavily on the building & safety folks to guide me through the process.

As best as I can remember, there was a flat sheet of sheet metal supplied by the mfgr. (Superior) through which the pipe exited from the dry-wall sealed compartment at the ceiling level. When the pipe exited the roof, it passed through a hole a bit wider (as per Majakdragon's suggestion) than the pipe itself.

BUT the pipe was held steady by the chase which was built to a height that followed the 10' rule. That is: the height of the chase must be at least as high or higher than a point of the roof 10' straight away from the exit of the pipe. Also, you must have a chase cover, a sheet metal cap with an exit sleeve that fits your pipe and covers the chase framing after it's sheeted. Usually this cover must be fabricated by a local tin smith. My chase was not square because of screwy roof framing, so the chase cover was shaped to match.

Hope this helps.

 

The top of the chimney pipe is supposed to at least 2 feet higher than when you level over from the roof to the top of the chimney, 10 feet. If you are short of the 10 feet before you intersect the roof on a level line, then you must go higher with the chimney until you have reached that 10 foot level line. (So therefore, you do not necessarily need to be 2 feet above the peak of the roof.) The idea of this is to guard against downdrafts when wind blows over the top of the roof from the other side of the roof.

 

The fireplace was one place I had the pro's do. The company I hired only has licensed employees and they did a great job. Inspector and insurance company liked them to.

Jon