Extending Hearth and the R Value Blues

Have you tried calling any stove stores in your area? They might have a sheet of Micore they will sell you, or tell you where you can get some.

Just thinking. Maybe you can use an air space instead. I know you only have 1 1/2 inches total to work with, but 1" of air space has an R value of 1.43. So, 1/2" would have an R value of .715. I know others here have used metal wall studs to create an air space for hearths. I know conventional metal wall studs are too large for your needs, but maybe you could find something like 1/2" square metal tubing. You could cut it to the length you need and have it on the bottom of your hearth or sandwiched between two sheets of Durock or whatever. The Lowe's down here has all types, lengths, as well as aluminum and steel.

BTW, I have also seen angle iron type metal pieces at Lowe's. It has holes along both sides and is thin steel, probably for shelves. You could cut those to length and have them sitting on the floor like a triangle. Side by side, they should be pretty strong.

I think you have a few options.

It would seem that the area in front of the ash lip would only need ember protection, since it is not getting direct radiant heat from the bottom of the stove.

If you want to go with air space you can buy Z furring. Any sheet metal shop can make them. You can have it bent to any dimension and space it however you like. I would recomend having them bent out of 20 guage galvanised. For instance if you needed to bring your hearth up 1/2" you would ask for 1 1/2" x 1/2" x 1 1 1/2' Zs. This would give you a nice inch and a half to fasten to to the floor and a inch and a half to screw your tile backer to. Be sure to buy self drilling screws for your tile backer. I hope this makes sence. BTW I am a steel stud framer by trade.

Air space is a great idea, but with 1 1/4" to work with, you are really made for building it up with Micore and never worrying about it again. Keep trying to find a Micore supplier - assuming you can afford the time, it's worth the drive or the shipping to just get the right stuff, and do it the right way. Thinset over your 1/4" Durock layer, set in the 1/2" Micore, then thinset and set in the 1/2" Durock, screw that all down, and then mortar your slate down.

Good luck and keep us posted!

you can buy micore here - don't know anything about pricing but phone number at that link for more info.

http://www.mantelsdirect.com/install/fireplace_surround_facing.html

I'm not sure if this will help at this point but I'll share what I learned. I just had my Hampton HI300 inspected and passed this morning. I was concerned with my extension but it passed. My manual stated "Thermal floor protection not required if unit is raised 3.5" min. measured from bottom of stove. At this point the standard ember floor protection will be required."

In my case the fireplace floor and hearth height is greater than 3.5" so I only need standard ember protection for the hearth extension. I am 8" short from the 18" extension mark so I bought a piece of brownstone to lay directly on the floor. I plan to have a wool rug on the hardwood floor and then lay the stone on top of that. I currently have the stone resting on 1/2" wood boards so the stone is not in contact with finished wood floor. The LLBEAN wool hearth rug is due in any day now.

I think the key difference here is the 3.5" of hearth thickness. Your picture suggests less than 3.5" but I can't be sure. If that is the case, you will need to meet the R value stated in the manual.

I hope this helps.

Good luck!

organic said:

Originally I thought I only needed ember protection up front, but the blower seems to blow hot air right in that spot. I am afraid I would be heating up the subflooring too much.

I may investigate using air space as Nic36 recommended. It looks like I need another trip to Lowes.

Click to expand...

Isn't that blower on the bottom blowing air out the top?? I would have thought ember protection would be fine. Anyway, glad you are on your way to what you want...