Shape of a brick chimney Design Styles, Chimneys and Finish Discuss Shape of a brick chimney in the Pizza Oven Design and Installation forums; I am at the final stages of my oven build. I have now started with my chimney which is a ...

[Jochen]

I am at the final stages of my oven build. I have now started with my chimney which is a simple brick chimney that sits on top of the front arch.
See picture.

So far the chimney is about 30cm high and it was recommended to me (from a non oven builder ph..) to make the top of the chimney narrower towards the end to increase the “upwards draft”.

Is that true?

Also, the inside of the chimney is very rough due to different sized bricks and my lack of brick laying skills. Does the rough surface have a negative effect on draft ability of the chimney? Is it worth rendering the inside of the chimney with fire mortar?

Any thoughts are very much appreciated

[dmun]

Also, the inside of the chimney is very rough due to different sized bricks and my lack of brick laying skills. Does the rough surface have a negative effect on draft ability of the chimney? Is it worth rendering the inside of the chimney with fire mortar?

I don't think it's worth messing with the inside of the chimney. The folks who build masonry heaters have largely concluded that a smooth transition isn't worth cutting a bunch of bricks. On the other hand, the rumford fireplace folks think a smooth curve is essential. It's a matter of opinion: mine is that smoke is a gas and will flow where it flows despite mini-turbulence caused by roughness in your smoke funnel.