Hearth Pad Construction - Need Advice

[plenzlerjm]

Hey y'all,

I'm building a hearth pad and would like a sanity check on the following construction.

On top of the hardwood floor, I'm putting down 1/2" plywood, then 5/8" Micore 300, then 1/12" galvanized sheet metal, then 1 3/8" thin brick pavers (no mortar).

I know I'm good with the R-value of the Micore alone as far as heat is concerned (I only need 0.59 for my stove specs).

I figured I could lighten up the hearth pad by omitting a layer of Durock and grout between the sheet metal and brick.

What do you think? Any suggestions?

 

[firefighterjake]

Most folks that use Micore say that due to its nature it is best to make a sandwich of it between cement board . . . then again most also use thinset to keep the stone, pavers, bricks, etc. in place.

Is there any particular reason for not using the Durock . . . I mean adding a sheet of Durock will make it a bit heavier . . . but unless you're planning on moving the hearth a lot that shouldn't be a real issue . . . if the weight concern is due to the weight of the hearth and stove I doubt the Durock will make that much of a significant difference.

 

[plenzlerjm]

Most folks that use Micore say that due to its nature it is best to make a sandwich of it between cement board . . . then again most also use thinset to keep the stone, pavers, bricks, etc. in place.

Is there any particular reason for not using the Durock . . . I mean adding a sheet of Durock will make it a bit heavier . . . but unless you're planning on moving the hearth a lot that shouldn't be a real issue . . . if the weight concern is due to the weight of the hearth and stove I doubt the Durock will make that much of a significant difference.

Thanks for the reply. I was concerned about the weight, but went under the crawlspace and reinforced the floor on a pier of concrete block, a 2x12 and bag of Sackcrete.

I think I'm good on the weight issue and will use the Durock.

Thanks! Joe

 

[rwhite]

I built a 2'x5' hearth extension and it weighed about 150lb. It had 1" plywood, 1/2 micore, 1/2 durock and ceramic tile. So you can use that (10 sqft) as a measure of what your's will weigh. Also important is how you spread that weight. My hearth would be about 15 lbs/sqft. That's like having a small child stand there. If the hearth is solid it will spread the weight of the stove across the hearth. So a 5x5 hearth would have the same lb/sqft weight as mine, add a 400 lb stove and you are still only about 31 lb/sq ft. Now consider a 400 lb fridge sitting on a 3x3 area , that's about 40 lbs/sqft. The big thing is to span as many joists as you can to spread the weight.

 

[plenzlerjm]

I built a 2'x5' hearth extension and it weighed about 150lb. It had 1" plywood, 1/2 micore, 1/2 durock and ceramic tile. So you can use that (10 sqft) as a measure of what your's will weigh. Also important is how you spread that weight. My hearth would be about 15 lbs/sqft. That's like having a small child stand there. If the hearth is solid it will spread the weight of the stove across the hearth. So a 5x5 hearth would have the same lb/sqft weight as mine, add a 400 lb stove and you are still only about 31 lb/sq ft. Now consider a 400 lb fridge sitting on a 3x3 area , that's about 40 lbs/sqft. The big thing is to span as many joists as you can to spread the weight.

Many thanks for the data and advice!