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I am now debating the style of WFO i want to build. I do know for sure that i will use the FB in a running bond pattern and the thickness of the walls will be 4" - 4-1/2" so there is no need for outer insulation. The issue that i am having is some say to dry lay the bricks and some say to use a mortar joint between the bricks. which way is correct?
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Re: mortar joints or not
I am not sure where you got your information, but the thickness of the thermal mass has nothing to do with the amount of insulation. In the first case, the amount of thermal mass has to do with how often, and for how much production you plan on producing, while the amount of insulation, both under the oven and on top has only to do with how much money and space you have to provide it. Skimp on insulation at your own loss. -
Re: mortar joints or not
My post was regarding the use of mortar joints or not for brick laying and not about skimping on insulation, space or money.
BTW 4" - 4-1/2" wall thickness for residential ovens is common but if you want 8" walls that's okay too.Comment
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Re: mortar joints or not
The compound curve required to build a dome would make a mortar-less build extremely difficult and brick cutting tediously accurate. The mortars purpose is to eliminate any gaps through which heat can escape.Originally posted by AJR View Post
Regarding the wall thickness a 4" thick wall for bricks is about the minimum. Folk have tried doing it thinner, but the mortar joins then invariably fail, because there is less mortar holding the bricks together. Cast domes are generally more like 2" thick because you are not relying on the mortar to hold the thing together. Thicker walls mean more thermal mass which means of course more heat stored for retained heat cooking, but a longer heat up time required. 8" thick walls may be ok for an oven that is used continuously like a bakers oven, but for home occasional use would take a ridiculous ly long time to heat and therefore use tons of fuel. Just decide how you would like to use your oven.
When some builders refer to mortar-less joins they are actually just referring to the appearance of the dome on the inside. ie. no mortar join visible on the inside of the dome. All this really does is to reduce the clean up required on the inside and reduce the possibility of little bits of mortar falling off the dome into your food (an extremely rare occurrence). It does not mean the joins between bricks are left mortar less. They are also usually backfilled with more mortar as well.Last edited by david s; 10-01-2014, 08:41 PM.Kindled with zeal and fired with passion.Comment
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Re: mortar joints or not
Thank you for the clarity, i understand. I have never seen a parge coating on the inside of a brick oven. A nice clean floated or brush interor brick dome finish. Would that help with sealing and insulation?Comment
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Re: mortar joints or not
No, not at all. The whole idea is to keep any mortar away from the interior surface. Certainly doesn't insulate, you want the interior surface to be as conductive as possible anyway.Originally posted by AJR View PostKindled with zeal and fired with passion.Comment
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Re: mortar joints or not
The wall bricks will constantly conduct heat away from the inner face of the cooking chamber, unless they are surrounded by insulation. It's possible to cook in an uninsulated dome, but you need to constantly replenish the lost heat by burning extra fuel. In a well-insulated oven, after the bricks heat all the way through, you only need to replenish the heat that goes into the food or out the door. Are you near the VT border? You could check out my build if you like.Comment
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Re: mortar joints or not
Vtsteve, I would love to check out your oven but i'm in Rockland county, about 20 northwest of NYC. I will insulate the oven and keep the site posted with pictures as i make progress.Comment
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