Hearth Design Help

[jimmiller2]

I am planning to install a England 13NC free standing stove on a 3/4 inch oak over 3/4 plywood floor. The manual calls for a R value 2 hearth minium of 4 foot by 4 foot. This sounds hard to achieve. Two layers of 1/2 inch durock with Micore sandwiched between (with ceramic tile on top) is what I am thinking in the initial planning stages. Any ideas, advice? How thick micore needed?

Thanks
Jim Miller

 

[Nic36]

I am planning to install a England 13NC free standing stove on a 3/4 inch oak over 3/4 plywood floor. The manual calls for a R value 2 hearth minium of 4 foot by 4 foot. This sounds hard to achieve. Two layers of 1/2 inch durock with Micore sandwiched between (with ceramic tile on top) is what I am thinking in the initial planning stages. Any ideas, advice? How thick micore needed?

Thanks
Jim Miller

I don't think that is going to give you an R value of 2.

1/2" Micore has an R value of 1.1. 1/2" Durock is .26, and the R value of tile is minimal. So, .26 + .26 + 1.1 = 1.62.

You probably need to use two layers of Micore, and then you will easily meet the required 2 R value. Or, maybe you can use air space.

Here is the hearth design link, if you have not seen it already.

https://www.hearth.com/econtent/index.php/wiki/Hearth_Design/

 

[jimmiller2]

Nic
Thanks. Now if I can just find where to buy Micore board. I am going to use two 1/2 inch layers with a 1/2 durock on top.

Jim Miller

 

[Nic36]

Nic
Thanks. Now if I can just find where to buy Micore board. I am going to use two 1/2 inch layers with a 1/2 durock on top.

Jim Miller

I think that is the tough part. It seems many here have a hard time finding Micore. I've never seen it around here. Maybe a stove shop in you area has some or can tell you were to get some.

 

[edthedawg]

One spot of advice: determine the exact footprint and location of the stove, and put yourself a little Durock square for better support in those areas. Just cut the Micore out around the squares. This will give you better direct support for the stove without compromising the insulation properties you require. I'd reckon 3" squares would suffice.

But carefully plan this out first - not only do you need to meet the hearth size minimum requirements, you also need to factor in the clearances from the back of the stove to the combustible wall/trim pieces. This may move your stove out further from the wall than you had originally planned, and could mean you will want a deeper/longer/wider hearth in the process... Don't just go by the R-value and minimum hearth size requirements alone!

good luck and post some pix for us later

 

[73blazer]

Nic
Thanks. Now if I can just find where to buy Micore board. I am going to use two 1/2 inch layers with a 1/2 durock on top.

Jim Miller

I think that is the tough part. It seems many here have a hard time finding Micore. I've never seen it around here. Maybe a stove shop in you area has some or can tell you were to get some.

YOu can become the supplier here!

(broken link removed to http://cgi.ebay.com/Micore-160-Board-USG-Product-55-sheets_W0QQitemZ270315403336QQcmdZViewItem)

 

[jimmiller2]

That link brings up a question. The board on EBAY is listed as Micore 160. I saw another board on an industrial website listed as Micore 300. Does anyone know if there is a specific number to be looking for?

Thanks
Jim Miller

 

[jimmiller2]

EdtheDawg

I too was wondering about the micore and how compressable it is. My plan is to go with a 4 by 4 hearth to utilize 12 inch tile and get two layers out of a 4 by 8 sheet of micore. It is going over hardwood floor so I was going to take the total thickness of all layers for example 2 micore, one durock, 1/4 inch tile and make a nicely finished solid oak frame with mitered corners and 4 foot inside dimensions. Drill thru the edge of this two inch tall 3/4 inch wide 4ft by 4ft frame and finish nail into place in the exact spot needed. I now have a perimeter for the heart firmly in place. Then cut two 4 by4 pieces of micore and drop in then cover with a 4 by 4 piece of durock made from two thickness of 5/16 durock so the joints will overlap giving a thickness of 5/8 inch. I will use structural adhesive to hold the durock together. Then tile over with 12 inch tile using thinset morter/adhesive followed by grout after tile sets. The durock/tile will be floating on top of the micore and hopefully the large 4 by 4 area will remain stable.

 

[edthedawg]

This is a great question. I think people usually use the 300, but the 160 has better R-value rating... I'm honestly unsure which is the better one to use...

 

[73blazer]

The only difference is the R & K-Values:

From (broken link removed) (put "micore" in the search box)

Micore 160: R/inch = 2.54 K=0.39
Micore 300: R/inch = 2.06 K=0.49

 

[jimmiller2]

Ed and 73 Blazer

I checked out the site listed and also found on that site a list of Micore distributors. One of which is in Huntsville, Alabama which is 50 miles away. Thanks for the help.

Jim Miller

 

[Nic36]

Ed and 73 Blazer

I checked out the site listed and also found on that site a list of Micore distributors. One of which is in Huntsville, Alabama which is 50 miles away. Thanks for the help.

Jim Miller

Interesting. I had no idea I could have bought Micore so close to home, although I did not need it for the stove I ultimately bought. However, I may have to build a hearth for my parents this summer and will need some.

Good find.

 

[ScottB]

put yourself a little Durock square for better support in those areas. Just cut the Micore out around the squares. This will give you better direct support for the stove without compromising the insulation properties you require.

This process will eliminate the insulating value of the micore in the area around the feet, where you need it most.
I used tile over durock over micore and it worked fine. If you do the math you will realize that each foot of the stove doesn't carry too much weight.
Got the micore at a local stove/chimney place.
Screwed the durock through the micore to the subfloor. I will be framing around the outside and doing hardwood on the rest of the floor. (In my spare time, ha ha).
It is currently framed in 2x4's for now. Picture is attached.