Duane's 42" Build

[Hamilton]

Good morning. Insulated the dome with 3" of blanket from our host at Forno Bravo and put the oven through five twelve hour days of drying fires. I ended up removing the perlcrete mixture around the base of the dome and used the blanket instead. It took me a minute but I found a crack in the dome that I was hoping to get lucky and avoid. Had a few of our kids, grandkids and one of the neighbors over for pizza yesterday afternoon. The best pizzas!!!

[MarkJerling]

Looking great. Well done!

[Hamilton]

Hey all.
I have attached a few photos.
One of the sealer/adhesive used to secure the chimney pipe base to the firebrick, rated at a much higher temp than what we are using. It is rock solid.
My chimney cap made of the refractory castable separated from the mortar. I already had concerns about that area due to the temps at the time and the mortar did not have a chance to cure as a opposed to drying out. Needs some suggestions at this point on how to secure the cap to the chimney? The dome will be intersecting the backside of the refractory chimney cap due to poor planning.

[UtahBeehiver]

I have seen some builders scoring or cross-hatching mating surfaces of bricks with an angle grinder and diamond wheel to reduce slippage and increase the mortar grab. May work here.

[Hamilton]

I will give it a try.
Can somebody remind me of the formula for the render coating and the thickness?
I have 3" of insulation so I think I can go straight the the hard shell.

[bencuch]

Hi Hamilton,

You have created a really beautiful building.
The floor bricks were glued to refractory concrete or laid freely on a mixture of brick and clay

[Hamilton]

Hello,

The bricks were laid on a 50/50 mix of sand and clay.

[david s]

I will give it a try.
Can somebody remind me of the formula for the render coating and the thickness?
I have 3" of insulation so I think I can go straight the the hard shell.

You can buy a premixed commercial render that has a degree of waterproofing, or make your own brew. A high proportion of lime give the layer a degree of elasticity. 4:1:1 sand, Portland cement and lime is pretty good and if you add 50/50 water and an acrylic fortifier, you’ll also get some partial waterproofing. Once perfectly dry an elastomeric acrylic coating can be applied to fully waterproof the surface if desired, but the outer shell then is not breathable. The addition of random fibres to the render mix makes mesh reinforcing unnecessary and saves lots of time. I usually apply this outer render in one go to around 12-15mm thick, basically to save time, but the recommendation is not to exceed 10mm and to be done in 2 layers. Use a wet sponge to smooth out tooling marks.

[bencuch]

Hi Hamilton,

You have created a really beautiful building.
The floor bricks were glued to refractory concrete or laid freely on a mixture of brick and clay

Good day,

I will also ask you for a small detail - you laid the bricks in a dry or wet mixture of sand and clay

[bencuch]

Good day,

I will also ask you for a small detail - you laid the bricks in a dry or wet mixture of sand and clay

Good day,

I will come back to my question.
When fine sand, stove clay and water are mixed, a sticky substance is created that would definitely stick the bricks to the refractory concrete. (so the mixture should be used dry, I mean)

Moisture must definitely be avoided and therefore it would probably be better to use fine fireclay dust (0-1mm).

[Hamilton]

Good morning.

I have seen it done both wet and dry but I did add water to the mix.

[bencuch]

Are there cracks in your oven or is everything OK?

[Hamilton]

Since the drying fires I have found one hairline crack in the dome starting at the base and goes about 3/4 of the way up.
My understanding is that all ovens will crack.

[fox]

Most one piece ovens will crack, segmented cast ovens are far less likely to crack because they have built in allowances that allow the oven to expand.
Take it slow with the drying fires, try to control the intensity and duration of the fires as gradually as your patience will allow.

[bencuch]

Thanks for your time. I'm at the beginning of construction and I also poured refractory concrete under the floor because of the heat bank and I'm about to lay bricks on the floor. David advised me to lay them loose without sticking them on a mixture of clay and sand. I think he is an experienced builder and I want to do it anyway.