Chimney Design

[pizzaben]

Hi all,

Been perusing the forum for a while and I am in the process of my 36" WFO build and had a question. For the chimney, would it be wrong to build my chimney completely out of fire brick? I think it will be around 24" tall and roughly 6"x8". Or would this create a weight issue on my arch? I would think the arch could hold approx 150 pounds of brick and mortar but maybe I'm wrong? If it is a weight issue then I could cut the firebrick in half long ways in order to reduce weight?

[SableSprings]

Welcome PizzaBen, glad you joined the forum community. For most folks, it's the added cost of using fire bricks where they aren't necessary...not the weight. There are lots of builds in the forum threads that use regular bricks in the chimney higher than two feet...many of those have an added buttress at the base of that support/front arch. If you had a bunch of fire bricks that you wanted to use in the chimney, yes they are heavier and usually a bit bigger than regular bricks...but done correctly, the arch is amazingly strong. Take a look at my chimney build for one buttress option for the arch supporting the chimney... I would do a better job now, but this was my first experience doing any brickwork. That said, finished the oven in 2009 and it's still in great working order.

[david s]

Hi all,

Been perusing the forum for a while and I am in the process of my 36" WFO build and had a question. For the chimney, would it be wrong to build my chimney completely out of fire brick? I think it will be around 24" tall and roughly 6"x8". Or would this create a weight issue on my arch? I would think the arch could hold approx 150 pounds of brick and mortar but maybe I'm wrong? If it is a weight issue then I could cut the firebrick in half long ways in order to reduce weight?

Apart from the weight issue that probably requires butressing on the sides of the arch, a brick chimney adds considerable thermal mass that acts as a heat sink, drawing heat from the oven during retained heat cooking which leads to shorter cooking times. This problem can be partly alleviated by insulating between the chimney and flue gallery which supports the chimney. This also then creates a structural weakness in the oven. A round chimney interior results in less drag than a square or rectangular one as does a smooth surface. So a round thin stainless steeel pipe reduces weight, as well as providing a far smoother airflow. For these reasons it is the preferred, but certainly not mandatory, solution for wood fired ovens.

[JRPizza]

pizzaben , I build mine out of firebrick and it has held up pretty well.