Pdx 42" update

[david s]

You could try applying a stucco/render coat directly onto the blanket, but it is a very poor substrate to work to. A vermicrete layer as well as providing additional insulation, sets up firm and covers bumps in the blanket, particularly if the top of the oven has an extra layer which creates a step (as in post #261)

[Macrinehart]

Thank you Gulf and david s for the advice.

There is one more area I have questions on before going too much further. This pertains to accounting for material movement during heating and cooling, particularly where different materials are interacting around the base of the chimney.

Elsewhere I've read that the oven dome may move during heating and cooling. I assume that the insulation layer helps to allow this movement without cracking the vericrete or stucco layers of the dome.

I have also allowed about 1/2" gap between the dome and opening arch which will be sealed with fiberglass stove gasket material. It's pretty tight but should allow for some minor flexibility.

Over the interior and exterior arch I will have a Stainless steel transition to the chimney, and because this connects to both the interior and exterior arches, I have my doubts about the best way to attach this piece. I'm thinking of using fiberglass tadpole tape, as I think it should help provide a good seal with some flexibility to isolate interior dome movement from the exterior arch and the vermicrete and stucco layers.

Finally, I intend to surround the base of the ss chimney transition with vermicrete and stucco in the back the insulation till butt up to the ss transition piece. My plan is to leave only the front face of the exterior arch exposed.

I am a little concered that as these different components heat and cool and interact I could start having issues.

Can anyone see any yellow or red flags?

Thank you!

[david s]

The expansion at our service temperatures amounts to about 3-4 mm every time you reach pizza temperature.

[Gulf]

I think that you have all of it covered as for expansion of the actual dome.The CFB is doing that. However, you need to make a place for the steam to escape during curing if you haven't included that in your design. Also, there will need to be something that will performs as an expansion joint between any ss steel and any masonry including the vermicrete. As for actual attachment to the chimney, I would like to see the "transition piece that you are using. Usually, it is just a heat resistant gasket that is homemade. Where ss bolts are used for the actual anchoring, oversized holes through the ss a good practice to allow for expansion.