Choice of concrete backer board and insurance safety

[worktolearn13]

I keep hearing conflicting opinions on using next gen durock for a Hearth pad construction, along with others as well. If i meet my R Rating with some of these products that seem to be "on the fence" for hearth pad qualifications, could i still find myself up the creek with an insurance co. if something were to happen? Also does things change if the install gets cleared by correct athorities?

 

[branchburner]

If you are compliant with codes and approved by local authorities, insurance should not be a problem. If something WERE to happen, I'd think hearth pad R requirements would be one of the last things on anyone's mind, since the likelihood of a fire being caused by a modern EPA stove with an "on the fence" hearth pad seems pretty remote.

That said, many prefer to go on the side of caution and exceed requirements by a lot... especially if there is a chance you may change stove and gets something that throws more heat towards the floor. I put a sheet of micore under my hearth extension.

BTW, welcome to the forums! What kind of stove are you putting in?

 

[worktolearn13]

Thanks excited for my first reply! I can see this type of project receives a lot of caution, I feel like I should lean towards the same myself so to make my wife comfortable haha. We are looking at installing a corner placed jotul F-3 CB with all of the work being done by myself. Learning so much and getting close to feeling confident.

 

[worktolearn13]

Good points also, I agree that if a fire were to get loose there would be bigger issues to focuse on then backerboard system that met the R value for safety. One other question I can't seem to understand for sure is the need for one inch air gap under the hearth pad I build. I definitely will have a 1" for the walls in the corner but should I keep the theme going underneath as well?

 

[begreen]

If you are concerned, then you can still get and use the original Durock which is pure cement board at R=.26. When in doubt, look at the MSDS sheet for the product and closely go over the list of components. Durock NexGen uses pumice as a filler which is quite non-combustible. Others like Hardibacker use some cellulose which make me a bit more circumspect. What you don't want to use is anything that uses styrofoam as a filler to lighten the cement board. Those products are commonly used as backerboard for wet locations like showers and countertops.

 

[worktolearn13]

Thanks begreen, Any thoughts on allowing a one inch air gap beneath the hearth pad. Planning on plywood laid on top of the carpet with 2x4 frame and plywood again. Then two sheets of next gen durock on top of that. completed by a veneer brick or stone I choose from menards.

 

[begreen]

The air gap between the top and bottom sheets of plywood doesn't count. The only thing that matters is the hearth insulation between the wood (top layer of plywood) and the stove. Two sheets of Durock NexGen would be R=.78. If that meets or exceeds the stove requirement then it's good to go.

You probably already know this, it's generally recommended to not put a hearth pad on carpet, but as long as the protection is proper then it's ok.

 

[worktolearn13]

Great thanks a lot for the help begreen. I sort of figured that was the case for the pad since the plywood has to support the concrete from breaking. I will be cutting the carpet the more I think about it there isn't a good reason not to. Thanks again hopefully I can start soon! Got to budget! Lol

 

[begreen]

Keep us posted on your progress. What stove is going in?