Building a Hearth Pad for an Unlisted Stove

[FrenchyRaoul]

Hello all,

I'm very new to hearth.com, but this site seems to be the place to go for wood stove questions!

I purchased a wood stove off of craigslist a few years back, and am looking to install it in my cabin. I have been reading a lot about hearth building, but wanted to check in here before I put it together, so I can make sure what I am doing is safe. First and foremost, I can't identify the stove I have, but the one post I found containing a similar stove identified it as a 'Tucker' wood stove. It has 'Allagash' stamped on the front. Here is an image of what the stove looks like:

Anyway, this is my current plan. I would like to build a heat shield out of brick, 1" off the wall, with a 1" air gap at the bottom. This should allow my clearance to be 12" off the wall with the stove. I plan to use ceramic spacers and concrete backer board, and affix my bricks to that. In order to support the bricks, I plan to use small 1" squares of brick or stone underneath the brick joints to support it, but only under the joints so as not to restrict that airflow..

I have less confidence in the hearth pad. Right now, my plan is to use four sheets of 1/2" cement backer board (Durock from Lowes), and top that with brick. It looks like that gives me at least (4*0.2R) + (1*0.4R) = 1.2R. I tried to be conservative with the R values, I know some backer board has higher than 0.2R. This whole structure would be floating (no screws, as they transfer heat?), on top of the floating laminate flooring.

I am hoping someone can let me know if this is sufficient? I am expecting to be told no, as a lot of the rules I found require 4" of masonry with sheet metal on top. I was hoping to have a brick top, as the sheet metal is not the look I wanted to go for. Some posts I found, people were sandwiching sheet metal between the backer board, but I'm not sure how that works. Is the purpose of the metal to reflect the heat? Can it still reflect heat when it is enclosed in backer board?

 

[FrenchyRaoul]

Perhaps a key detail—the clearance under the stove is less than 6". It is closer to 5"-5 1/2'. I have since found and read the sticky in the forum. Table 2 indicates I need 4 inches of hollow masonry and sheet metal on top. As I mentioned, I was hoping to not have sheet metal on top, is there a way around this? Also, I'm not quite sure I understand what hollow masonry that allows ventilation means. I know CMUs have holes in them, would you use a bunch of CMUs on their sides so air can flow in and out? That sounds ugly AF, to be honest.

Any help is appreciated!

 

[begreen]

The floor protection for an unlisted stove must extend 18" from the stove in all directions. The hearth requirement will depend on the leg length.

NFPA Hearth info:
12.5.1.2.1 Room heaters, fireplace stoves, room heater/ fireplace stove combinations, or ranges that are set on legs or pedestals that provide not less than 6 in. (152 mm) of ventilated open space beneath the fire chamber or base of the appliance shall be permitted to be placed on floors of combustible construction, provided the following conditions exist:
(1) The floor under the appliance is protected with closely spaced solid masonry units not less than 2 in. (51 mm) in thickness.
(2) The top surface of the masonry is covered with sheet metal not less than 24 gauge [0.024 in. (0.61 mm)].
(3) The floor protection extends not less than 18 in. (457 mm) beyond the appliance on all sides.

12.5.1.2.2 Room heaters, fireplace stoves, room heater/ fireplace stove combinations, or ranges that are set on legs or pedestals providing 2 in. to 6 in. (51 mm to 152 mm) of ventilated open space beneath the fire chamber or base of the appliance shall be permitted to be placed on floors of combustible construction, provided the following conditions exist:
(1) The floor under the appliance is protected with one course of hollow masonry units not less than 4 in. (102 mm) in nominal thickness.
(2) The masonry units are laid with ends unsealed and joints matched in such a way as to provide free circulation of air through the core spaces of the masonry.
(3) The top surface of the masonry is covered with sheet metal not less than 24 gauge [0.024 in. (0.61 mm)].

 

[FrenchyRaoul]

I see. So a bunch of these should work?

https://www.lowes.com/pd/Standard-C...al-3-625-in-x-7-625-in-x-15-625-in/1000241905

It sounds like I can seal off the ends on the outside of the hearth, so long as I don seal any of the interior holes. Maybe the standard 8" would work better, however.

Is there any way to not have metal on the top of the hearth pad? That is, any equivalent protection, that would allow tile or brick? Or all all hearth pads without a metal surface not up to code?

 

[jetsam]

Cinder blocks and sheet metal! I like the guys that wrote that code.

 

[begreen]

Brick, 4" block will both work. I believe the intent of the metal is to stop any embers from falling between cracks and to act as a radiant shield. Speak with your local inspector but I would think a layer of 1/2" Durock and then grouted tile, stone or brick veneer on top would also suffice.

 

[jetsam]

I am no expert, but a strict reading of the above would seem to require you to use "hollow masonry units" turned so that the open ends butt each other and are open to the room, if the clearance is under 6".

 

[FrenchyRaoul]

Awesome, thanks! I don't even know where to start finding a local inspector, to be honest.

My plan is then, 4" concrete blocks, topped with 1/2" Durock, and then grouted paver bricks. I'll throw would trim around the whole thing once I'm done.

Simple as can be, thank you @begreen !

EDIT: @jetsam are the blocks I posted not considered hollow? They are cored. Do you have an example of what you considered a 4" hollow masonry unit?

 

[begreen]

How tall are the legs on the stove? They look at least 6" but best to measure.

 

[FrenchyRaoul]

I'll measure again tonight. But I think they are about 5 1/2".

 

[jetsam]

Perhaps a key detail—the clearance under the stove is less than 6". It is closer to 5"-5 1/2'.