In Progress with a Plan

[From_IT_to_PIZZA]

Thanks rasorface - I think I have a good plan now.

Not much progress last weekend but we did get the counter top installed.



This weekend's focus will be on the insulation layer (5 part perlite and 1 part Portland cement) of 2inces. My plan is to use the bottom of the doghouse I previously cut out as my template. It almost seems like its too big for the slab and I may need to make it smaller.

If I cut the doghouse another 6inces from the bottom I think it may allow me to use that extra 4-5inchs for the casting.





Once dried I will place the firebricks on top and start to line up the area for cutting.

I will also try to start on the refectory cement mix with refectory stainless needles and start to get the dome going.... Lets see how far I get.

Any suggestions from anyone would be appreciated.

[david s]

Most builders using vermicrete consider 4” rather than 2” to be adequate. Although it is a cheaper alternative than calcium silicate board, its disadvantages are that it requires a lot of water and the mix to be placed wet, cured and dried. This takes time rather than the cal sil which is placed dry. Using drain holes through the supporting slab and arranging the vermicrete to be raised slightly from the supporting slab with some tiles creates small channels where moisture can find its way to the drain holes. This assists greatly in the drying of the vermicrete as well as any future moisture ingress. If doing this operation for wet vermicrete, some weed mat or aluminium insect screen should be placed over the tiles to prevent the wet vermicrete from blocking the tile channels and the drain holes.

[From_IT_to_PIZZA]

Thanks david s

If I go with the Cal Sil do I just place this direct on top of the supporting slab? And do I just place the firebricks direct on top? No need for sand to level it?

Question on the chimney > I purchased a 6" but it has a 6" wide inter diameter and an 8" outer diameter..... Do I make my hole in the oven casting 6" or 8"?

[david s]

If you go with cal sil it is still a good idea to do some drain holes under the insulation and the tiles to elevate it, but you can skip the aluminium screen or weed mat.
Regarding the flue, you have what is called as a double flue. With that set up you can mount the inner pipe as I did and arrange the outer pipe to sit outside the outer render which prevents any risk of water entry and eliminates the need for high temp silicone.

[From_IT_to_PIZZA]

So just drill 4 or 5 holes 1/2inch or 5/8th into the slab? Or would I need more? What type of tile would you suggest use? Sorry for all my questions.

Understood on the flue. Makes sense.

I may start tomorrow on the refractory casting and needles and get that first layer put on before I decide on what to do with the insulation base.....

[david s]

Yes 4-5 1/2” should do, but use 5/16” pilot holes first to reduce blow out. It is also a good idea to seal the top of the supporting slab with some stone and concrete sealer before placing the tiles to prevent moisture wicking up from the stand, into the supporting slab and into the tiles. If you hit reo start somewhere else. Any tiles will do, just space them out so enough will support the insulation and floor bricks but leave channels for moisture travel to the holes.

[From_IT_to_PIZZA]

I put 5 hole and some old tiles from another project.... I think I am good on this but skipped the weed mat so I hope this will be okay going forward.

The perlite and portland mix was super easy to work with and the 4" insulation layer was a breeze to complete. I have it now with a damp towel on top covered with a tarp....






The refectory cement and needles were a little harder to work with compared to the percrete and at first the refractory cement was sagging and molding on its own.... I figured it was too wet and I ended up adding more cement until I was able to crumble the chunks, and at that point I was able to mold it to how I wanted.

Unfortunately I think I may have ruined it by not having enough cement. I purchased them about 2 months ago so I cant recall how I did my math but its obviously wrong. I purchased 6 buckets of 25lb each and they were about $55 each so its not cheap and they are special order so I can just go and pick them up. This is how far I got >




Is it okay to continue when I get the others 25lb buckets due to arrive in about 3 days or will I need to start from scratch? Do I need to toss what I did so far or can it be reused?

Thought about maybe mixing the refractory cement with perlite but not sure if this is the right way.....

[From_IT_to_PIZZA]

The additional buckets of refractory cement have arrived and I plan to just continue and see what happens. Not sure if I have much of a choice at this point.