Hearth Specs for a Jotul 500

[Simonkenton]

I have the Jotul brochure, it gives the clearance specs for the back and the sides etc, but it doesn't give the specs for the hearth.

What I am planning to build will go on a floor of 3/4 inch plywood, beneath that will be 2x10 joists.

I am planning to put down a layer of that 1/2 inch concrete board that you set tile on, then put big flat rocks on top of that in a bed of mortar. These rocks will be about 2 inches thick, on about a 1/2 inch thick bed of mortar.

So, the Duroc and the mortar and rocks will total about 3 inches thick.

 

[jeff_t]

Manual says 'UL 1618 Type1', which is ember protection only. Your plans will be fine.

 

[Simonkenton]

OK thanks a lot.

 

[firefighterjake]

As mentioned only ember protection is needed with the Oslo . . . your hearth plans are fine.

 

[begreen]

I would add a sheet of plywood beneath the cement board for stiffness. One sheet of Durock is not enough to provide this.

 

[firefighterjake]

What I am planning to build will go on a floor of 3/4 in

I would add a sheet of plywood beneath the cement board for stiffness. One sheet of Durock is not enough to provide this.

I agree . . . I missed that . . . misread actually . . . thought you were planning to build on top of 3/4 inch plywood . . . now I see that you are saying it is 3/4 inch plywood for the subfloor. Yeah, definitely add a sheet of plywood . . . heck, two even wouldn't hurt . . . you don't want any flex once you have mortared in the stones. Nothing worse than to have the hearth all pretty like and then have it crack or stones break since it could flex with the weight of the stove.

 

[Cynnergy]

I used this deflection calculator to make sure my hearth tiles wouldn't crack: http://www.johnbridge.com/vbulletin/deflecto.pl

It gives a rating number for natural stone too.

We ended up putting a support in for the joist from below because we had really long joists (24' long 2x10's - we put the support in the middle so that in effect the hearth is on a 12' long 2x10). No cracking yet.

 

[Simonkenton]

I have installed tile on 2 bathroom floors in houses that I have built, and of course I put another half inch of plywood on top of the 3/4 plywood subfloor. I appreciate y'all giving me the heads up, hopefully I would have remembered in time but, of course, for this massive masonry install I would need at least another sheet of 3/4 plywood, as begreen said. Hell I might even add 2 sheets of 3/4 ply, it wouldn't hurt.

 

[begreen]

We used 1 1/8th ply on our bathroom floor before tiling it in 2006. It is solid as a rock. You could move an Equinox in there (if you wanted a very hot bathroom!).

 

[Simonkenton]

You are correct begreen, 1 1/8 inches subfloor is the spec for tile, and I think I will increase it a little for my Jotul. Three inches of masonry and a 450 pound wood stove.