Hearth construction questions

[stranger]

Hi guys,

We need your help. We recently bought a house with old wood stove (Fisher brand). The stove sits on a 1 ft high brick platform and connected to a masonry chimney. We are thinking of replacing the stove with Mansfield soapstone. My husband wants first to remove the brick platform and put 3 layers of Durock and porcelain tile on the top of it (to reach 0.8 R-value required by Hearthstone). My questions are:
1. Is it necessary to obtain permit or contact building inspector to do the hearth replacement?
2. Is it ok to put all these layers (and the stove itself) on the top of normal subfloor (23/32” plywood) or some kind of floor reinforcement is required? Any recommendations? What is plywood load capacity? Sorry for the stupid questions. I was trying to read the posts here before asking but could not find clear answers.
Please help.

 

[JimWalshin845]

Hi guys,

We need your help. We recently bought a house with old wood stove (Fisher brand). The stove sits on a 1 ft high brick platform and connected to a masonry chimney. We are thinking of replacing the stove with Mansfield soapstone. My husband wants first to remove the brick platform and put 3 layers of Durock and porcelain tile on the top of it (to reach 0.8 R-value required by Hearthstone). My questions are:
1. Is it necessary to obtain permit or contact building inspector to do the hearth replacement?
2. Is it ok to put all these layers (and the stove itself) on the top of normal subfloor (23/32” plywood) or some kind of floor reinforcement is required? Any recommendations? What is plywood load capacity? Sorry for the stupid questions. I was trying to read the posts here before asking but could not find clear answers.
Please help.

1: No... not if you are just replacing or upgrading.... but I would definitely check first with your local code enforcer.

2: As long as the current code is met as per the installation instructions... nothing wrong with going bigger, more durable and deeper.

Welcome aboard and ask more questions!

 

[begreen]

Welcome stranger, hope you won't be one for long . No worries about the load. The Fisher is not a light weight either. The layers of durock and subfloor will distribute the weight evenly. A normally built floor can take a lot more than the stove's weight. Think about it, a couple hefty guys can weigh about 4-500#s.

 

[elmoleaf]

Is the existing hearth part of a stove install at an existing fireplace opening?

Typically, when you remove the bricks from a hearth like that, you'll find a concrete hearth extension underneath, which extends from the below the firebrick inside the firebox to about 16" beyond the front face of the fireplace. If replacing something like that, your new materials (durock etc.) will be spanning across the concrete and over onto the wood subfloor construction surrounding the hearth extension. In that situation, it's probably better to try to keep the weight of the stove on the hearth portion supported by concrete, but not strictly necessary given all the blocking around the concrete.

If it's a hearth on wood (no fireplace), then the your weight should be fine, as long as the durock begins and ends directly above floor joists/blocking. Otherwise there's a small chance you could have some flex in the install, leading to cracked tiles. It really depends though on how the joists run, if any blocking was added, how screwed down etc.

 

[Gooserider]

Hi guys,

We need your help. We recently bought a house with old wood stove (Fisher brand). The stove sits on a 1 ft high brick platform and connected to a masonry chimney. We are thinking of replacing the stove with Mansfield soapstone. My husband wants first to remove the brick platform and put 3 layers of Durock and porcelain tile on the top of it (to reach 0.8 R-value required by Hearthstone). My questions are:
1. Is it necessary to obtain permit or contact building inspector to do the hearth replacement?
2. Is it ok to put all these layers (and the stove itself) on the top of normal subfloor (23/32” plywood) or some kind of floor reinforcement is required? Any recommendations? What is plywood load capacity? Sorry for the stupid questions. I was trying to read the posts here before asking but could not find clear answers.
Please help.

As far as I know there is no permit requirement on the hearth repair / replacement as such, but you ARE required to get a permit and inspection on the stove replacement, and the inspector WILL look at the hearth, along with any other clearances, your chimney, etc. at that time. Be ready to document just what you've done to build the hearth, and to show that what you've done meets code / instruction manual requirements.

I'd also be cautious about removing that brick platform - make sure that it isn't supporting anything to do with the masonry chimney!

When putting down the Durock, be sure to put a layer of thinset down between each layer, and screw everything together with the appropriate length of Durock / Cement board screws (NOT drywall screws!) as described in the Durock documentation (which you should print out and save for the inspector - it's good to document that it is code appropriate) - this will significantly increase the strength and rigidity of the floor assembly.

Gooserider