39 inch build NI

[balon]

So following on from my initial post https://community.fornobravo.com/for...rthern-ireland

I've laid 4 inches of a 50/50 mix of perlite and vermiculite concrete insulation and have gotten some regular firebricks for the floor. I'm strongly leaning away from using the storage heater bricks.

The insulation layer is 48 inches in diameter allowing for a 39 inch floor and 4.5 either side for the dome. I understand from the plans that building the floor inside the dome allows for changing of a damaged brick in time if needed but how often does that happen and are there other advantages?

I'm looking for thoughts on whether it's better to cut the floor bricks to a 39 inch diameter and sit the first course on the underfloor insulation or whether to make a 48 inch floor and have the first course on the edge of the floor bricks.

Thanks!

[Whiterk]

What did you use to bend the circle as a form?

[balon]

What did you use to bend the circle as a form?

It’s flexible hardboard cut to size. Comes in an 8x4 sheet. If you’ve ever thrown out an old wardrobe, the backing board is very similar

[mongota]

"I'm looking for thoughts on whether it's better to cut the floor bricks to a 39 inch diameter and sit the first course on the underfloor insulation or whether to make a 48 inch floor and have the first course on the edge of the floor bricks."

I chose to have the floor bricks independent of the dome. With pro's and con's for both methods, I'm not certain if one way is technically better than another regarding thermal or structural performance that actually affects the oven itself. I see theoretical and sort of common sense advantages to having the floor bricks independent of the dome. But I haven't read of anyone with integral floor bricks having structural issues with their domes down the road. The moderators, being more familiar with posts on these forums, may be able to help with that.

My floor bricks are set in a herringbone pattern. Due to inherent irregularities in the edges of the bricks, slight gaps will occur between the floor bricks as they are set. These gaps can accommodate brick movement during thermal cycles. Over time, these gaps do fill with ash.

When I built my dome, during first year of use, while it wasn't necessarily easy to do I could remove a brick from the floor. After years of use with the gaps packed with ash, it's much more difficult.

Best, Mongo