My build, New Zealand.

[MarkJerling]

Nice job Mark. Not sure what part of NZ you're in but I know much of it can be really wet. You can greatly assist water elimination by drilling a few 1/2" holes up through the concrete supporting slab into the underfloor insulation to provide a path for water vapour drainage. Water will move away from heat and steam pressure build up will assist in forcing water and steam down through the drain holes.Damp insulation does not work too well and once the underfloor insulation is perfectly dry the oven will perform far better.

Hi David. Thank you. I'll not try to drill the slab at this point as there's far too much steel in it to drill it successfully. However, the underfloor insulation was kept dry throughout construction so, apart from some spills that did occur, there should not be too much moisture down in the (sealed) autoclaved layer. I could drill in sideways through the brick mortar joins and check moisture content using a moisture meter but it should be reasonably dry in there. With it completely sealed off from any potential rain ingress, I would imagine that the slab moisture will gradually dissipate. What remains to be seen is how waterproof the 3-coat plaster system is going to be. If it proves to be not perfectly waterproof I may need to paint it or at the very least, add a clear penetrating sealer coat.

One interesting thing is how long the oven holds it's heat. We made fire in it Sunday late afternoon and now, some 42 hours later, the oven still has a little warmth to the bricks.

[david s]

Nice job Mark. Not sure what part of NZ you're in but I know much of it can be really wet. You can greatly assist water elimination by drilling a few 1/2" holes up through the concrete supporting slab into the underfloor insulation to provide a path for water vapour drainage. Water will move away from heat and steam pressure build up will assist in forcing water and steam down through the drain holes.Damp insulation does not work too well and once the underfloor insulation is perfectly dry the oven will perform far better.

[MarkJerling]

[MarkJerling]

[MarkJerling]

Hi all.

Here's my build. 42" floor, 21" high dome. Started with a good hole in the ground and proper foundation as we live in earthquake prone country.

Then, using some bricks I got from a friend about 15 years ago, I built up the base. On top of the base, a reinforced slab and, on top of that a 3" aerated autoclaved concrete layer which has good insulation properties and acts as a base isolation layer for the oven on the base.

The whole oven including the oven floor is made from old night-store heater fire bricks. These are heavy, dense bricks that hold heat for a long time. For the base, I used large bricks / tiles from one large night-store heater, set on compacted sand. The oven dome itself is built from night-store heater bricks too, but these have been cut in half so as to provide a 5" thick dome. As a bonus, they have a little lip on one side so, by setting that to the outside it's been easy to build the curve of the dome. All mortar work has been done with refractory cement.

For insulation I used aerated autoclaved concrete under the floor as mentioned above, vermiculite cement and empty wine bottles around the base, 1" furnace blanket with 8" fibreglass blanket over that and aluminium foil over that. Over the top of it all I have a chicken wire mesh and 3-layer waterproof plaster. I can't decide whether to paint the outside (when I paint the house) or whether to leave it cement coloured. Thoughts?

The flue is an old secondhand 8" stainless steel flue. It draws quite well although I get some smoke out the door opening when I make a big fire. There's no smoke out the door with a normal fire.
I look forward to hearing your comments. I'll have to do another post as it seems I can only add 6 photos per post. More to come...