Fireplace Modification Ideas for Standalone Woodstove

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landrand

Member
Oct 24, 2006
48
Negaunee MI
I’m in the planning stages of remodeling my home in Northern Michigan (Upper Peninsula). Our winters are severe with frigid cold temps. I’ve decided to remove the existing old and useless fireplace insert and install a standalone Hearthstone Heritage wood stove I recently bought and pipe it through the fireplace chimney.

The house is currently about 1500 sq. ft. In the next 2-3 years, I plan to add on to the house so I anticipate the house to someday be around 2,200 to 2,500 sq. ft. My existing fireplace opening is 25 ¼†high by 36†wide by 17†deep and the hearth extends into the room 16†and is raised 10†off the floor. The living room is 15' 4" x 19'. The fireplace is on an external wall so thermal mass isn’t on my side for heating. To accommodate the Hearthstone Heritage stove, I need to add at least 6†to 8†on the Hearth to accommodate the 20 ½†depth leg spread on the Heritage stove. To be able to accommodate a larger stove in the future, I may want to even consider adding more than 8†to the existing hearth. This is where I seek recommendations from the pros.

Here’s a few modification ideas I'm currently considering:

The first idea is to remove the top layer of bricks across the whole width and build out the hearth 8†using the removed bricks. On top of the extended hearth, I would install something like a 24â€x 8’ slab of limestone or granite for the stove to sit on. I would then place the stove on top of the hearth and pipe it into a T and stainless steel chimney liner. I’m not sure how well it would work to have part of the brick hearth extended out onto the floor, yet part is still attached to the masonry fireplace. Since wood “moves a littleâ€, wonder if the extended bricks and mortar will eventually crack.

Another option would be to make it look something like the attached picture, which is from the Quadra Fire website. The idea would be to take down 2 or more layers of brick on the hearth in front of the fireplace opening, and extend the hearth out onto the floor in the immediate vicinity of the stove rather than extending it all the way across the whole width. For the area under the "cubby hole" I would remove all the hearth bricks. I would then cover up the whole brick fireplace, to include the fireplace opening, with some kind of cultured stone or veneer (like in the picture). I would completely cover up the fireplace opening and have a 6†thimble hole that I could use to pipe the stove into a hidden “T†connected to the stainless steel chimney liner. The existing fireplace has a clean out opening on the bottom. At the bottom of the T, I could pipe it to the clean out chamber. The actual clean out is located on the outside of the house on the bottom of the chimney. As shown in the picture, I think it would look nice to just have a stone wall with the woodstove sitting on some kind of low hearth pad. I could build the pad larger so it would be able to accommodate any size woodstove I may potentially use in the future. Underneath, I have a 4' crawl space and I plan to brace the floor joists with extra supports to ensure adequate support for a heavy stove.

Any ideas or recommendations from the guru’s would be greatly appreciated.
 

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The Quadrafire promo shot is impractical, there's no way the space could be kept that clean. It's very pretty but it wouldn't last long, and your existing photo shows what typical wood appliance places look like over time when they get used.

In your situation much will depend on the depth of the room immediately behind the photographer. Does the increase in hearth depth make the room cramped? Also, what's under the hearth and / or tile flooring? I wouldn't think there would be a lot of problems extending the hearth by 8" at least and covering the whole thing with a piece of stone. I would think you'd have a lot of options here to make something that's visually pleasing.

good luck

steve
 
I included the "quadra fire" picture to convey the concept of removing, more or less, the whole hearth. And then somehow build a suitable and code conforming pad for the stove to sit on just in front of the fireplace opening.
 
I like the idea of a much wider hearth to handle kindling box, wood stash and tools. That is the 'mess" that comes along with a stove. It's nice to keep it organized.

Don't worry about bracing. Three stoves are going to weigh less than that removed brick.
 
Dont discount the themal mass advantage, even if the masonry is exterior. My freestander is a hearth with an outside chimney and i get great thermal transfer and good thermal carryover long after the flames are gone.
 
landrand said:
I included the "quadra fire" picture to convey the concept of removing, more or less, the whole hearth. And then somehow build a suitable and code conforming pad for the stove to sit on just in front of the fireplace opening.

Understood, I just think it's funny that stove manufacturers like to promote their products in environments that would be very difficult to maintain...I mean come on, beige carpet?

At any rate, you could try to pull the hearth completely out but then you'll be forced to place the stove completely outside the firebox, which could do if you really wanted to, but who knows what's under that masonry hearth. I could see a stove partially set into the firebox but also extending forward onto the hearth, perhaps on a piece of stone or cast concrete that's bowed in front and cantilevered out over the existing brick hearth. You would have to probably install some steel underneath in order to support the outer portion of the stone / concrete but it could be done. You could also remove the top layer of bricks and cast it in place of those, something about 3" thick or so.

The gist is you have a lot to work with if you have the space in the room to deal with the extra masonry. I have a cut limestone bracket that was originally used to support a bowed window sill on a brick doublehouse which I can picture underneath the overhang of a new bowed masonry hearthstone.

good luck

steve
 
I drew up a couple of fireplace modifications idea's to support a standalone woodstove. I used sketchup and converted them to a .png file. See my next post for the for the second illustration as I couldn't load both of them at the same time due to their size.

Since I dont' have a wife, I need help in making a decision as to which one I should go with. What do you think? Should I go with just extending the hearth only in front of the fireplace opening or should I extend the hearth all the way across.

I bought some cultured stone to reface the existing brick. I bough 6-7 boxes of leftover (brand new) dutch quality sienna ledgestone from a 3rd party project. I paid about $2/sq ft which wasn't too bad. This stone is around 2" thick.

At this point, I'm not sure how to build out the hearth. Should I call a mason and have him extend the hearth with cement blocks, or whatever or should I just use metal studs and build a frame and cover with durock, micore 300, etc. I was able to find some micore 300 in the area so that is one less headache. I will need to remove the existing top layer of bricks to ensure I have enough clearance for the stove pipe to get back to the liner T.

The final piece will be the hearth top matieral. The top could be something like limestone, granite, bluestone slabs. I need to do more research to figure out what would be best to use. The existing chimney hearth will be resting on a concrete foundation and the hearth extension will be sitting on the subfloor, I worry about the difference in expansion between the two materials. Any tile or concrete work spread across the foundation and subfloor seems like it could potentially crack due to the subfloor not being as rigid as the concrete foundation.
 

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I think that will work fine. The hearth is raised enough so that I think only ember protection will be required for the floor section which shows a tile skirt. For example, look at the Homestead's fireplace installation requirements. This setup would be better with a right-side loading door on the stove like a Keystone. Less mess with the wood storage right there.
 
You're a single man? Well, that sure makes things a WHOLE lot easier bro! I could have done my install in about 1/3 the time if I didn't have to clear everything with the "Design Committee."

As has been noted, I think a lot depends on what the rest of your room looks like, how much floor space you have to work with, etc. Me-my-own-personal-self? Putting a stove out front of the hearth, like in the promo shot is the least attractive option. Integrating the stove to the existing hearth/face is a much more pleasing aesthetic. I would also opt for the first illustration over the second as symmetry is always going to be more pleasing to the eye. (Also, more space for tools, and a great place to sit, catches the wood "crumbs", etc.) But, those are personal preferences and I'm not the guy who is going to be looking at it every night, right?

With about 12" of hearth height to work with, it doesn't look like you'll have any issues with sufficient R values under the stove. If you are worried about total weight, a framed and sheathed hearth would obviously be the lightest. Is your existing hearth over a block foundation underneath? Should be. In that case, an extension is not going to bring much weight to the wood structure. Rigidity will be the key to the build out. You don't want any defection--- along the long dimension especially. Overall weight is not going to be a reall concern if you are doing the framing/cladding option, but "flex" would be. Narrowly centered steel studs, overlayed with Durarock sandwiching thinset would be plenty stiff. If you do want to put in some jack studs in the crawl space, that is an easy thing to do and probably will give you more than an margin against deflection and cracking.

Good luck and keep us posted.

mo
 
BeGreen said:
I think that will work fine. The hearth is raised enough so that I think only ember protection will be required for the floor section which shows a tile skirt. For example, look at the Homestead's fireplace installation requirements. This setup would be better with a right-side loading door on the stove like a Keystone. Less mess with the wood storage right there.

So BG if the hearth is raised you can go ember only ? It makes scense but... OP may want to check with insurance agent, I could see some insurers and maybe some code enforcement peeps, saying that it will not change the manufacturers requirements and yadda yadda yadda poo. Just to be safe it may be wise.
 
Hearthstone requires a non-combustivle hearth with an R value of 1.2 and 16" minimum hearth in front of the stove, if I'm reading it correctly. A built up, hollow hearth would have plenty of R value due to the air space, but run the calculations for sure. Be sure to calculate the total hearth width (rear clearance + stove depth + 16") to make sure your stove and hearth will fit your room.
 
There is a cement foundation under the existing hearth. The three bricks, mortar, and top slab will provide an R value greater that 1.2 directly below the stove. I understand that I need to check with the insurance agency, but I would surely think that a stove elevated off the floor more than a foot would only need ember protection for the 8 or so inches past the raised hearth (tile part).

Although I currently have the Hearthstone Heritage stove, I want to design so in the future I can potentially install a bigger stove on the hearth if needed. Maybe something like the new Woodstock Hybrid. The nice think about this stove is you can pick what side to have the side loading door.

I'm a little concerned about weight. I think it would be a good idea to put a couple of jacks stands under the floor joists for extra support.
 
shawneyboy said:
BeGreen said:
I think that will work fine. The hearth is raised enough so that I think only ember protection will be required for the floor section which shows a tile skirt. For example, look at the Homestead's fireplace installation requirements. This setup would be better with a right-side loading door on the stove like a Keystone. Less mess with the wood storage right there.

So BG if the hearth is raised you can go ember only ? It makes scense but... OP may want to check with insurance agent, I could see some insurers and maybe some code enforcement peeps, saying that it will not change the manufacturers requirements and yadda yadda yadda poo. Just to be safe it may be wise.

That is what I usually find in for stoves that are documented for hearth use. Air is a pretty good insulator and the radiant heat is mostly forward. They usually require 2-4" of hearth height. In this particular case it looks like he has about 10-12", so I would present that to the inspector or permitting authority.
 
Would it be ok to build the hearth extension with wood framing. Something like the following: 3/4" plywood over joists, 2x6's or whatever to box in the extended hearth frame, 3/4" plywood over frame, micore 300, two layers of durock, then some kind of 1 1/2" stone slab.
 
How thick is the Micore? If 1/2", that combo will exceed the R=1.2 requirements for the Heritage. With Durock NextGen it will be about R=1.8.
 
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