Chimney through a roof

[NoPineapple]

Living in a cold climate with rain and snow during winter time, I am planning to build a roof above the perlite pizza oven that I am currently building.

However, I am not sure how to avoid the hot chimney melting/burning whatever material I use for the roof.

Should I simply use sheet metal for the roof and cut a hole for the chimney? Or would I be better of using an angled chimey, simply letting the chimey protrude underneath the roof instead?

Any ideas would we really appreciated!

[MarkJerling]

The simple solution is to have a dual wall or triple wall flue pipe, which means that the hot (inner) chimney flue is not in contact with any building materials which may be a fire risk. You should avoid having a hot flue within 18" of any combustible building materials.

[david s]

EYou should have a double flu, ie a second larger diameter pipe that surrounds the inner one. The inner pipe should be stainless but you can get away with the outer pipe in zinc alum coated steel or similar. There should be a 25mm (1”) space between the pipes eg a 6” surrounded by an 8” pipe. Even the outer pipe is required to be at least 50mm from anything flammable like timber beams.

[JRPizza]

You might want to consider both, metal roof and double walled insulated pipe. I built a metal roof over a plywood deck. I cut a bigger hole in the plywood and a tighter hole in the metal roof, then used a silicone boot around the pipe to seal out the elements. Pipe never gets too hot to touch even when firing the oven.

[Chach]

I used a double wall stainless pipe through a plywood roof covered with a metal corrugated roof. The brand of pipe I used was Supervent and it only needed a minimum of 2" of clearance from combustible material. I cut the hole in the plywood 2"-2.5" bigger than the pipe. I did build a chimney on top of the roof so I didn't use a pipe boot to seal. I have a limestone cap that I put on top and siliconed around the pipe and installed the storm collar to keep the elements out

[NoPineapple]

Thanks for your suggestions guys.

I am planning on adding a "bushing"/socket in the concrete on top of my arch. This seems like the easiest way to mount the chimney itself. Any disadvantages of using a socket like that?



Regarding the isolated chimneys that were mentioned.. I guess I am looking for something like this?



A pricey solution that will probably be the most expansive part of the build, but I guess its probably worth it. Currently looking at 15 cm (6 inches) x 50 cm (19.68 inches). Does this sound reasonable for a pizza oven made with a 75 cm (29.5 inches) fitness ball?

[NoPineapple]

Bonus question.. I am planning to build the oven with a 10 cm (4 inches) layer of concrete/perlite. How hot can I expect it to get on the outside, without further insulation?
The chimney in my answer above consists of 2 layers with insulation between. According to the specs, it should have 10 cm (4 inches) clearance from combustible materials. How hot can I expect that to get?

Would bitumen roofing be a solution, or would that be classified as a combustible material?

[NoPineapple]

Sorry for the spam.. Found this for sale locally. Could that be used?

Insulated stove pipe. Internal diam 150mm/4in, external diam 200mm.