Woodstove hearth remodel

User514

New Member
Jan 13, 2021
3
United States
Hi there! New member here. I'm running into alot of issues finding the information I'm looking for. Ive read quite a few posts from here & figured I could just join and see if I can get all my questions answered in one place. This forum seems to have the best information regarding woodstoves.

Now to the fun part. I'm in the process of remodeling my current woodstove surround. It is torn back to the bare studs. Id like to build this for reduced clearances as I haven't decided on a new stove quite yet. Currently I have a pretty old cast iron one that is quite heavy.

My plans are below. Ive broke the walls and base down separately.

Walls- Rockwool in the wood stud exterior walls, followed by a layer of durrock. Then frame out on top of that a 5'x5' corner with metal studs (3.5" airgap) & then cover that in durrock, then stone. This would run to the ceiling so I'd place soffit vents in the durrock/stone at the top and bottom to provide the proper air flow.
1. Do I need to have sheet metal somewhere within this build?
2. Would you make any changes?

Base- I was originally planning on the following, in order from floor to stove: wood 2x4s, 3/4" plywood", durrock, thick stone (1.5-2"), woodstove. After looking around more I have concerns that I wouldn't be allowing proper airflow & not enough rock between combustibles. Ive seen pictures of people building bases with metal studs but personally have my doubts with the stability. (The studs I purchased for the walls are 20g)
1. Are 20g studs acceptable as a base for a heavy stove? How close? 8"?
2. Is there a need for sheet metal in this application? (I ask this because multiple woodstove manuals seem to reference 24g metal)
3. Would I need 1 or 2 layers of durrock?
4. Is the plywood needed? Seems counterintuitive to put a combustible there if I use metal studs but I also don't want it caving in under the legs after a few years.
5. Would you make any changes?

Any help would be appreciated! Thanks.
 
  • Like
Reactions: Shrewboy

Shrewboy

New Member
Oct 15, 2020
20
Eastern Pennsylvania
I recently put together a similar setup, what wood stove do you have?
It seems like most modern wood stoves don't require all the clearences/air gaps in between material that old ones did, so I would check the manual for your stove to see what it says about clearence.

I personally attached the duraboard / concrete board right to the drywall (screwed into studs) I am getting the Hearthstone Castleton 2020 model Catalytic stove, here is a pic of my finished setup:

20210111_202447.jpg
 

User514

New Member
Jan 13, 2021
3
United States
I recently put together a similar setup, what wood stove do you have?
It seems like most modern wood stoves don't require all the clearences/air gaps in between material that old ones did, so I would check the manual for your stove to see what it says about clearence.

I personally attached the duraboard / concrete board right to the drywall (screwed into studs) I am getting the Hearthstone Castleton 2020 model Catalytic stove, here is a pic of my finished setup:

View attachment 271858
Looks good.

The stove I currently have does not have a manual. It is very old, but still works. Therefore I need to build this to accommodate it until i replace it. When I do replace it, it will be with one of the larger models on the market.

How did you do the base? Metal, wood, or pavers?
 

begreen

Mooderator
Staff member
Nov 18, 2005
85,972
South Puget Sound, WA
The plan is serious overkill for an old stove. There is no gain in clearance reduction below 12". That is minimum. For the simplest shield you could build out the studs with 1" spacers, attach the Durock to the spacers, allowing 1" opening at the bottom and open at the top. Then veneer with stone. To make the spacers more stout to handle the stone weight, cut long 3" wide strips from the 1/2" cement board and double then up to create 1" thick firring strip spacers on each stud. Screw every 8" with 2" cement board screws.

Also remember that single-wall stovepipe has a clearance req. of 18" and that trumps the stove 12" clearance unless the pipe is also shielded. Double-wall stove pipe only requires 6" wall clearance.
 

User514

New Member
Jan 13, 2021
3
United States
The plan is serious overkill for an old stove. There is no gain in clearance reduction below 12". That is minimum. For the simplest shield you could build out the studs with 1" spacers, attach the Durock to the spacers, allowing 1" opening at the bottom and open at the top. Then veneer with stone. To make the spacers more stout to handle the stone weight, cut long 3" wide strips from the 1/2" cement board and double then up to create 1" thick firring strip spacers on each stud. Screw every 8" with 2" cement board screws.

Also remember that single-wall stovepipe has a clearance req. of 18" and that trumps the stove 12" clearance unless the pipe is also shielded. Double-wall stove pipe only requires 6" wall clearance.

Appreciate the feedback. The justification for it being "overkill" is to make sure I'm covered from an insurance standpoint if something were to happen. The excessive 3.5" airspace is because I have the room & i find it easier to work with vs laying them flat.

What would your method be of doing the base?
 

begreen

Mooderator
Staff member
Nov 18, 2005
85,972
South Puget Sound, WA
There really is no benefit, it would be easy to document that the clearances are met or exceeded without the additional stuff. But if that brings peace of mind then so be it. The new stove may require none of this.

Same for the base. It depends on the stove's hearth requirements which we don't have yet. Plywood is good, it not only provides something to securely screw into, it also stiffens the assembly and provides a good base for the cement board. As far as what goes on top of this, again it depends on the stove's R value requirement. If you are trying to meet the generic NFPA 211 requirement you will need to build up to R=1.19 insulation between the plywood and the top surface. There are multiple ways to accomplish this with many layers of NexGen cement board or a layer of micore under cement board.

And yes, no need for metal studs when the plywood is the nearest combustible. I would use wooden studs underneath.