Foundation base.

[AJR]

Hi All,
Maybe you can help. I plan on building a 32" diameter dome oven. I have a 50"x50" heavy duty steel frame table with a heavy slab of oak. The table is capable of holding 800+lbs. Here is my issue: After treating the wood, I want to install 5/8" cement board over the oak then, install a layer of builders sand then, install the firebrick oven flooring. Is this method OK? should i add remove materials? any help appreciated.
Thanks.

[SableSprings]

Re: Foundation base.

The sand and cement board alone will not be adequate heat protection for the wood base when you are heating the oven up to baking/dome clearing temps. I wouldn't go with less than 4 inches of the ceramic/cal-sil insulation board between the sand and hearth bricks.

Personally, I really hate to see a solid slab of oak being used as a base for a WFO...mostly jealousy though, since I'd love to have something like that as a workbench for making bread.

[jeeppiper]

Re: Foundation base.

INSULATE !!! You have to isolate the wood from the oven chamber. The firebrick, sand, and cement-board will all conduct heat right into the wood. I agree with Sablesprings on the insulation board.

[AJR]

Re: Foundation base.

Thanks for the input and i will for sure insulate and speculating on materials. How's this? From the oak base upwards install 2 layers of 5/8" fire resistant cement board then, install 12"x 12" ceramic tiles tightly butted with no joints, then install the insulation board and then the hearth bricks.

[AJR]

Re: Foundation base.

Thank you for your input and for sure i will insulate. I'm speculating on methods, how's this. From the oak base upwards i will: install two layers of fire resistant 5/8" cement board then, install 12" x 12" ceramic tiles with no joints then, install the insulation board and then the hearth bricks.
Thanks, Anthony.

[SableSprings]

Re: Foundation base.

Thank you for your input and for sure i will insulate. I'm speculating on methods, how's this. From the oak base upwards i will: install two layers of fire resistant 5/8" cement board then, install 12" x 12" ceramic tiles with no joints then, install the insulation board and then the hearth bricks.
Thanks, Anthony.

Fire resistant simply means the cement board will not burn easily...however it still will transfer heat as will the ceramic tiles. I think your main concerns are to protect the wood from moisture and heat while keeping your fire/heat in the intended oven chamber . One layer of cement board will be just as good as two...and the ceramic tiles won't really accomplish anything in the long run. The layer of sand is primarily to help you level the cal-sil/ceramic fiber insulation board(s) and offers very little insulation capabilities. In this case, the ceramic insulation board material (immediately below your hearth firebricks) will be the only effective defense against heat moving towards the oak.

I'm not sure about condensation between the cement board and oak in your N.Y. humid summers and reasonably cold winters...unfortunately I think having an effective, long-term moisture barrier between wood and almost any other material is going to be somewhat of a challenge for an outside WFO.

[boerwarrior]

Re: Foundation base.

one more consideration... I have a 32 inch Pompei oven and I used close to 200 firebrick in my oven. My yellow firebricks weigh 9 pounds each. 200 x 9 = 1,800 pounds - much more than 800 pounds. Are you sure your base can hold the weight?

[AJR]

Re: Foundation base.

Holding the weight is no problem. The steel frame alone is 200lbs and the oak top is at least 150lbs. I see the steel frames that are sold for bases and mine is stronger by far. The frame has heavy stitch welds plus, for a belts and suspender approach i will add more steel bracing.