cooking floor layout on perlcrete questions

[George T]

Quick Question.

I have my perlcrete done and am will be ready tomorro to start my floor for my hearth. This stuff is a little crumbly and certainly cant be drawn on. I used CVDUKES method in Tips.....it worked well, but is more crumbly due to the lower amount of portland, but I think it should have better insulation properties.

My questions.....
1. Any tips for making sure the floor is set right?
I thought about just going square and then draw on the oven floor.

2. I am also a little worried that using the notched trowel will cause some of the perlcrete crumbs to move.... is that an issue?

3. Most of the pictures I see in the "oven plans" dont appear to have a top with porosity from perlcrete. Did I do something wrong?

Thanks again.
GT

[dmun]

The best way to align the floor bricks is to line them up on the floor in the pattern you want, and measure how far from the side you want them. Then start from that point and lay them out from there.

You want something on top of the perlcrete to smooth it out for your bricks. The original method (is this still in the plans?) was to make a paste of fireclay and sand, and trowel it on with a notched trowel. The idea was that you could press down any proud bricks into the paste. It's been learned that a dry powder (either the fireclay-sand mixture, or refractory mortar) laid out on top of the perlcrete works better. Once you get your bricks where you want them, you wet them to solidify the underlayment.

[SpringJim]

I would think this is an area where the builder should not be too concerned about having a little bit thicker layer (paste/powder/sand) under the hearth (say 1/2 inch to an inch?) as it will only be a little additional thermal mass which for many is a plus.

We put a lot of weight on that perlcrete layer....I'm assuming compression of that insulation layer has not been an issue for anyone.

[George T]

If I use Fireclay.....What is the proporation of sand to fireclay in the mixture?

Thanks.

[asudavew]

I did this to my perlcrete floor for the reasons you have stated.




I used the poor man's high temp mortar. I'm trying to remember the formula...

I'm sure it's in the E-book

[George T]

Thanks. I will check in the Ebook. I think it is 1:1.

[Dutchoven]

1/3/1/1 portland/sharp sand/hydrated lime/fireclay should work well although you could probably just go with a fireclay and sand mixed to a thinset type consistency
Best
Dutch

[asudavew]

i'd leave the lime alone.. if I had a do over.

very caustic

[George T]

I used just the sand and fireclay in a dry mix per Dmun's advice and then wetted the brick to solidify. I used a 2 parts sand to 1 part fireclay mixture. Hope that will hold ok.....since I was not using any portland I was hesitant to use too much sand. Any concerns from the experts?