[simbadCA]

The furnace installed inside a closet is being replaced. The platform supports the gas furnace and provides a return air vent prior to he filter. The original plywood platform had drywall on top of it, and the furnace on top of the drywall.

I don't like the drywall for the platform, however I am looking for an alternative non-combustible material.

 

[gregzoll]

Drywall is the typical material used under a furnace, if the manufacturer calls for it in their installation manual.

There is no other alternative non-combustible material.

 

[oh'mike]

See if Hardibacker (tile backing board) will meet the requirements---

 

[Bud Cline]

See if Hardibacker (tile backing board) will meet the requirements---

Hardiebacker doesn't fit the bill I don't think, but any of the other cement boards will.

 

[yuri]

You may want to stay with drywall and put some galvanized tin/sheetmetal on top of it if you want it to be more durable. In my experience the gas inspectors have very little imagination and unless you have documentation to prove the other material meets the gas code etc they may shut you down. Not worth the huge hassle to deal with them and that IMO. You can get galvanized tin at HDepot or any HVAC shop.

 

[simbadCA]

Thanks for the response. The installation manual only indicates non-combustible material. That's likely the solution I will go back to. I believe that Hardibacker will still transfer the heat, and I wanted to avoid the silica dust if left uncovered.