RMH on a wood floor

I am attempting to build an RMH from the 6" Daybed plan from Ernie and Erica's plans. I am unsure how to build the platform above the floor and how to contain the perlite insulation layer. I have beefed up the joists under the footprint of the stove, so that part seems good.

What the pics below show is 1/2" durock on concrete brick on edge spaced every 12 ". The total footprint of the stove in roughly 3x10 feet.
My questions are 1. does my construction look ok so far, and 2. How to hold the perlite on the durock sheet, and how deep for that matter.
By the way, great forum, I've learned a ton.

Hi Lorne.

Well, i would put two more layers of sheetrock myself. As for holding the perlite, with clay? Metal? Bricks? Whatever you feel like and is not flamable.

Satamax,

Thanks for that, but to be clear the sheet material I am using is a cement board (Durock) sold over here in N.America. So, you think a total of three layers or about 1.5 inches?
Cool, thanks I was wondering how many pounds per square inch it could take. I guess I should put a thin layer of thin set mortar between each layer.
I have some nice old brick, likely 2 courses would give a good base volume for the perlite.

thanks

LB

Myself, i wouldn't bother with mortaring the durock, but that's because i'm lazy.

I think mortar between layers of durock would bind them thermally more, increasing the heat conduction - the opposite of what you want. If anything, I would add thin spacers, like 1" wide strips of durock every few inches, to increase the resistance to heat flow.

But the durock supported evenly by bricks spaced a few inches apart should make a fine base for the perlite-clay mix. With bricks spaced a foot or more apart, I actually would have concern about a single layer of durock, and would consider doubling it up, though I think the better solution would be doubling the number of support bricks so there is not such a wide gap to span. If you are concerned about load-bearing ability, increase the clay ratio a bit in the base layer. Several inches of that plus a good air gap ought to work fine. With a firm edging, the perlite-clay has nowhere to spread to.

Another thing I would suggest is to add a layer of aluminum foil on top of the base bricks, shiny side down, to give some reflective insulation. The foil should go on top facing down instead of bottom facing up so the shiny face to the air doesn't get dusty and dull and lose the reflective barrier effect.

Glenn,
Thanks for that feedback, I was quite worried about the spacing of the bricks, as I came by the 12" spacing without much evidence. Hey, bricks are cheap ($.35 each). So, I'll go every 6 inches with the bricks supports then.

"the book" says to glue 2 layers of aluminum foil on the wood floor. Doesn't that reflect radiant heat away from the wood? But I guess foil above and under the bricks couldn't hurt.

Thanks again.

LB

Shiny aluminum foil facing an air space in either direction will resist heat radiation - it's a property of physics that a shiny metal surface does not radiate or absorb as much heat as a dull or rough surface. It must be facing an air space, though, or there can be no reflection. Foil has no meaningful resistance to conductive heat transmission, as you would get if it were sandwiched between two other materials. It would work the same under the bricks facing up, but it would get dusty over time and lose effectiveness.

Good point, foil on the floor would not be clean long in my shop, thanks.