Confused on how to build hearth

JSL10

New Member
Nov 2, 2015
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Central Oregon
Just purchased a Hearthstone Mansfield wood stove. This is for new construction so we are at exposed studs and OSB floor right now. I want to build a corner raised hearth (about 10" or so). What I was planing on doing was to frame out the hearth with 2x8's. Then on that base, add a layer of plywood and then a layer of concrete backer board then rock that the stove would sit on. Then on the back wall studs behind the stove, I was just going to put a layer of concrete backer board directly on studs and then matching rock.

The Mansfield has two clearance numbers for the corners (8" for protected and 14" for unprotected). Would this be adequate to meet the protected distance (NFPA 211)? Thank you!
 

begreen

Mooderator
Staff member
Nov 18, 2005
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South Puget Sound, WA
Nice stove! The new Mansfield hearth needs an ember protection only so you are ok with your plan. The wall however needs to be ventilated to be an NFPA 211 wall shield. This means floating the cement board on 1" non-combustible spacers and open at the top and bottom by an inch so that air can freely convect behind the wall shield. Ceramic spacers are sold or you can make your own out of copper pipe or long 3" wide strips of 1/2" cement board that are doubled up to make firring strips.

Here's an article on the topic:
https://www.hearth.com/talk/threads/wood-stove-wall-clearances-primer.147785/
 

bag of hammers

Minister of Fire
Jan 7, 2010
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Northern ON
In my previous install (with heat shield) I used a piece of metal drywall furring channel - cut into pieces - for spacers behind durock board. Just another idea....
 

moosetrek

Minister of Fire
Oct 22, 2008
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Eastern Nevada
10" is a decent height for the hearth, you might want to double check that you will still have sufficient clearance from the top of the stove to the ceiling afterwards too.

Good luck!
 

JSL10

New Member
Nov 2, 2015
9
0
1
Central Oregon
One more question on the 14" to the "Unprotected Surface" specification... can that space have non-combustible materials in it or does that need to be 14" of air? What I mean is that I have enough space to have 14" to the studs. So inside that 14" can I have a single sheet of fiber board and rock (i.e. not deal with spacers & airflow behind, etc.)? Hope that makes sense.