Beefing Up & Expanding Hearth for Wood Stove

[danbrellis]

Hello everyone,

First time poster, about to get a wood stove (thinking about VC Encore Flexburn, but that's not why I write) and want to vent it out of an existing fireplace. The fireplace had a 1" think slate slab that sat on several layers of mud bed, mortar, and piled rocks/concrete. I need to extend out the hearth for the wood stove and want the new hearth level with the existing brick of the fireplace bottom. I got a new slate piece that is 60" x 32" x 0.5".

I cut out the existing hardwood floor to the new size of the hearth, pulled up the (cracked) slate and the top layer of mud deck, and then another ~1" layer of some kind of mortar bed. I'm left with (from the fireplace and moving out) a pile of rocks held together with concrete that sit on earth. Then a gap (where the subfloor was), then half a width of log floor beam before the hardwood starts up again.

My plan was to fill in the big open space with layers of rock and high strength concrete to make level with the existing concrete pile. Then pour the high strength concrete over everything with a remesh embed to about 3" shy of the fireplace bottom. Then level off with a cement self leveler (about 1" thick). Then layer 3 layers of 0.5" durock on top of the cement for r-value. Then thin-set mortar the slate to the durock.

However, I ran into the issue of not knowing how to attach the durock to the newly poured cement level (could I just embed it in there, use concrete fasteners?). I know you should only attach to wood or metal. Any other way to get the r-value I need (1.06)? I don't think the concrete by itself would cut it.

Thanks for any input!

 

[edyit]

https://chimneysweeponline.com/horvalue.htm

that link will give you some r values of items used in hearth building

 

[begreen]

I suppose the Durock NexGen could have screws projecting into the wet cement. That would anchor it pretty well, but it will bond to the cement.

If you haven't purchased the stove yet, you might want to look at alternatives that have an ember protection only requirement.

 

[Blue Heron Hideaway]

How far away is that log going to be from the front of the stove

 

[danbrellis]

How far away is that log going to be from the front of the stove

About 16" from the front. We gave 18" from the front of the stove to the edge of the slate hearth.

 

[kennyp2339]

I'd rethink the whole VC woodstove thing, the company has been sold and resold a umber of times, they still use the orginal casting but have had to change the internal parts to meet the newer epa guidelines, unfortunately these changes to the internal parts have created a generation of stoves that have failed and have rather costly repairs (although some stoves have lasted to) If your going for the "classic" look check out Jotul stoves, they are more reliable and possibly less hearth protection.

 

[Blue Heron Hideaway]

I think that log is your main issue. nothing else under their is combustable

 

[Blue Heron Hideaway]

how big an area you trying to heat

 

[danbrellis]

I'd rethink the whole VC woodstove thing, the company has been sold and resold a umber of times, they still use the orginal casting but have had to change the internal parts to meet the newer epa guidelines, unfortunately these changes to the internal parts have created a generation of stoves that have failed and have rather costly repairs (although some stoves have lasted to) If your going for the "classic" look check out Jotul stoves, they are more reliable and possibly less hearth protection.

Thanks for the input. I have definitely read lots on VC and I think a jotul would be nice, but I need the stove to vent out the back to fit into the existing fireplace and none of the jotuls had a rear vent that was low enough to get under the brick. This VC I believe is the only one that fits our circumstance.

 

[danbrellis]

how big an area you trying to heat

About 2000. It's half of the house on the main floor and above it.

 

[Blue Heron Hideaway]

whatsthe height of the brick

 

[Simonkenton]

"(thinking about VC Encore Flexburn, but that's not why I write)"

But this should be why you write.

You are making a big boo boo if you buy a Vermont Castings. What led you to the decision to buy this stove?

 

[danbrellis]

We did a lot of research about wood stove options and based on our measurements narrowed it down to 1, the VC Encore.

If you come to a different conclusion, I'm all ears. The hearth depth (measurement E) will be 32". We want the stove to vent into the existing chimney and (preferably) sit inside the fireplace a few inches to give back some depth into the room.

 

[Blue Heron Hideaway]

The jotulOslo f500 rear vents and have a height of 261/2. gets good reviews on this site.Just another option.

 

[Blue Heron Hideaway]

what's your budget

 

[Pertzbro]

Check dimensions on this. Is a better running stove, comparatively priced. Better company and i think the clearances are even better..

https://www.woodstove.com/index.php/progress-hybrid#PH flue collar

 

[Pertzbro]

Their other stove should also work. Adjustable leg height. Is also relatively cheap..

https://www.woodstove.com/index.php/ideal-steel-hybrid

 

[Blue Heron Hideaway]

I am going to do the same thing you are but going with the Jotul 500. I think it is cheaper than the VC but is not a catalytic. If you are using your existing chimney are you having a liner put in? Alot of these stoves wont vent good without it.

 

[danbrellis]

The jotulOslo f500 rear vents and have a height of 261/2. gets good reviews on this site.Just another option.

Thanks for the recommendation, but with those clearances, the hearth would be sticking out almost 2 feet further into the room than the VC would need to be. The room is wide and not deep relative to the fireplace, so we are trying to minimize how far it sticks out into the room as much as possible.

CORRECTION: actually, if the stove could be backed right up to the fireplace (but not inside), it would stick out 27.25", plus the 18" hearth extension would put it out into the room at 45.25". Not 2', but still a full foot further.

 

[danbrellis]

I am going to do the same thing you are but going with the Jotul 500. I think it is cheaper than the VC but is not a catalytic. If you are using your existing chimney are you having a liner put in? Alot of these stoves wont vent good without it.

Yes, we're going with a liner for sure. Our local dealer says a single liner is fine, but we're considering a double liner anyway. The other thing we liked about the VC is that it has way lower emissions than many of the other comparable stoves we've seen. For us, that was important.

 

[Blue Heron Hideaway]

The liner only needs to be single but should be insulated. Their are a few chimney sweeps on this site that can steer you in the right direction. Just start a new thread. Good luck.

 

[Blue Heron Hideaway]

That is a nice stove.

 

[danbrellis]

I suppose the Durock NexGen could have screws projecting into the wet cement. That would anchor it pretty well, but it will bond to the cement.

If you haven't purchased the stove yet, you might want to look at alternatives that have an ember protection only requirement.

Thanks begreen for being the only one to give an answer to my actual question

I think I will try that. I don't see a downside in the durock being bonded to the cement...

 

[vwmike]

Thanks begreen for being the only one to give an answer to my actual question

I think I will try that. I don't see a downside in the durock being bonded to the cement...

The proper way to adhere the durock down would be with a 1/4x3/8 notch trowel and thinset. This ensures full contact and support of the board, and will be the strongest by far.

 

[bholler]

Personally if I were doing the job I would support those framing timbers on either side cut them out then pour a new slab. Then there is no need for r value. And it meets code for an open fireplace as it should