perlite strength

[Joesmoe45]

Hi Everyone,

Is 1" perlite cement (5:1) on top of slab strong enough to support my dome?

[vtsteve]

Re: perlite strength

A one-inch thick layer of perlcrete (if I understand you correctly) won't have enough insulation value to even bother doing. The compressive strength is fine, it just won't be an effective barrier to the heat leaking from your floor and into the slab.

Perlcrete/vermicrete insulation is generally used in a 4-6" minimum thickness. Thicker is better.

[Tscarborough]

Re: perlite strength

Perlite at 8 to 1 is strong enough to support your dome, but as noted, 1" is not enough, you need 3-5"

[NCMan]

Re: perlite strength

Perlite at 8 to 1 is strong enough to support your dome, but as noted, 1" is not enough, you need 3-5"

I agree. I used it @ 1:8 and it works fine. Also, the thickness you use will have an effect on the final height of your hearth floor, so you may want to be cognizant of that. Most builders prefer the final height of their floor (top of bricks)to be about 42" or slightly above their elbow height. I made mine @ 42" and if I had it to do again, would probably make it 44-46", although my shorter wife likes it just fine. You can adjust that to meet your needs. Also, you may want to consider a vapor barrier in between the layers. My 2?.

[moderator]

Re: perlite strength

Our fully assembled products range in cooking height between 38" and 45" with the taller ones more common commercially (to see in the oven easier while cooking). The lower heights are for the small residential ovens where the user wants a comfortable height for working the peel.