Modifying an existing firebox?

[sparkymiller]

Hello seasoned hearthers!

I'm looking to install a wood insert into the fireplace of my 1950s un-insulated 800sf cottage in southern Ontario Canada. We like to spend time there not just June-Sept, but also into the cooler shoulder seasons.

I got quote from a local installer for four different inserts. They didn't really answer my questions, which brings me here, to hearth.com, so that I can really understand the issues when I'm getting a quote from someone else

The fireplace is in the middle of our open living/dining dining room with high ceilings. It's a stone shell, with an old steel firebox. (see attached photos)

I want a simple modern insert (like a Morso 5660b or a STUV 16) that sits flush with the stone. (See attached collage for an idea)

I know it's not as thermally efficient to have it flush, but my goal is to add a bit of heat to make the chilly visits more comfortable, and to dry out the damp—I'm not expecting that this insert will provide full heating to the cottage. Also don't want a blower - there's no electrical near the fireplace and I want simplicity.

The quotes for all four inserts included several hundred dollars for a hearth rug and when I asked about that, they said that the existing hearth wasn't deep enough.

That's when I took my own measurements and drew it up, and compared it to the inserts I wanted, and realized that none of them, installed inside the existing steel firebox, would have been flush with the stone, they would be sticking out 4-6" and that's why the existing 19" hearth isn't enough.

I asked about modifying the firebox at the back corners (to square it up a bit) - like cutting into the sides and welding new steel, so that the firebox is big enough to fit the inserts. They said no way.

Which I don't understand.

Why can't I have a welder modify the firebox to make it a bit wider at the back corners?

I also don't want to have a hearth rug, and think that enlarging the existing hearth would be tricky (or maybe not?)

I would also be willing to look at installing a small stove in the fireplace if it's way more thermally efficient and easier to install.

Thanks in advance for your input and advice!

Anne

 

[bholler]

Hello seasoned hearthers!

I'm looking to install a wood insert into the fireplace of my 1950s un-insulated 800sf cottage in southern Ontario Canada. We like to spend time there not just June-Sept, but also into the cooler shoulder seasons.

I got quote from a local installer for four different inserts. They didn't really answer my questions, which brings me here, to hearth.com, so that I can really understand the issues when I'm getting a quote from someone else

The fireplace is in the middle of our open living/dining dining room with high ceilings. It's a stone shell, with an old steel firebox. (see attached photos)

I want a simple modern insert (like a Morso 5660b or a STUV 16) that sits flush with the stone. (See attached collage for an idea)

I know it's not as thermally efficient to have it flush, but my goal is to add a bit of heat to make the chilly visits more comfortable, and to dry out the damp—I'm not expecting that this insert will provide full heating to the cottage. Also don't want a blower - there's no electrical near the fireplace and I want simplicity.

The quotes for all four inserts included several hundred dollars for a hearth rug and when I asked about that, they said that the existing hearth wasn't deep enough.

That's when I took my own measurements and drew it up, and compared it to the inserts I wanted, and realized that none of them, installed inside the existing steel firebox, would have been flush with the stone, they would be sticking out 4-6" and that's why the existing 19" hearth isn't enough.

I asked about modifying the firebox at the back corners (to square it up a bit) - like cutting into the sides and welding new steel, so that the firebox is big enough to fit the inserts. They said no way.

Which I don't understand.

Why can't I have a welder modify the firebox to make it a bit wider at the back corners?

I also don't want to have a hearth rug, and think that enlarging the existing hearth would be tricky (or maybe not?)

I would also be willing to look at installing a small stove in the fireplace if it's way more thermally efficient and easier to install.

Thanks in advance for your input and advice!

Anne


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No insert is going to be totally flush so with your 19" hearth extension won't meet the Canadian requirement of 18". You will need some sort of extension. Atleast here a hearth rug isn't adequate for that

 

[stoveliker]

If you can find a small stove that fits in there, it'd be more efficient in giving heat than a flush (or almost flush) insert without blower. The convection around the stove will push much more heat out.
Regardless (stove or insert), you need to put in an insulated block-off plate to ensure that the heat does not rise between the the chimney liner and the stone chimney (and then heats the great outdoors).
And you'd need floor protection regardless of whether it's a protruding insert or a stove (as the stove will protrude too).

 

[begreen]

That big crack in the hearth will need to be repaired regardless.

 

[sparkymiller]

No insert is going to be totally flush so with your 19" hearth extension won't meet the Canadian requirement of 18". You will need some sort of extension. Atleast here a hearth rug isn't adequate for that

Thanks @bholler I may have been looking at images of european installs where the face of the insert was almost recessed into the fireplace

 

[sparkymiller]

That big crack in the hearth will need to be repaired regardless.

Yup @begreen for sure! If I'm extending the hearth, maybe there's a (straightforward) way to form up and pour an extension (maybe pouring a bit higher) and tie it into the existing. Because it's unheated I worry a bit about seasonal temp fluctuations and cracking on any new pour.

 

[sparkymiller]

If you can find a small stove that fits in there, it'd be more efficient in giving heat than a flush (or almost flush) insert without blower. The convection around the stove will push much more heat out.
Regardless (stove or insert), you need to put in an insulated block-off plate to ensure that the heat does not rise between the the chimney liner and the stone chimney (and then heats the great outdoors).
And you'd need floor protection regardless of whether it's a protruding insert or a stove (as the stove will protrude too).

Thanks for telling me about insulated block-off plates @stoveliker ! I will look into small stoves as an alternative to an insert.

 

[30WCF]

Not sure about the rules there, but with the right ember protection only stove, I could imagine it looking nice if you cut a large sheet of steel in the shape of a “T” and inserted the leg of the T into the firebox (cut to fit) and had the wings of the T extend the width of the existing pad, and as deep as the new stove required.
It looks like the part that would need to extend forward would need a shim to level it. Maybe some hardy backer or an exact fit may need some strips ripped on a table saw to shim the difference from the existing pad to hardwood floor. Trim it in some rough cut or moulding to smooth the transition.

Another option is tile for ember protection, but I suspect there may be movement in different seasons and conditions between the wood floor and the pad. So just adding backer board to the wood to level it, then tiling the whole thing is likely going to crack across the union.

A small/medium free standing, rear vent stove with a steel extension and a block off in the chimney would get my vote for ease of installation. Just depends on how much you want to modify.

 

[bigealta]

Will a fireproof mat stapled to the floor meet the regulations in canada?

 

[sparkymiller]

Will a fireproof mat stapled to the floor meet the regulations in canada?

might!‾\_(ツ)_/‾ I don't know, but will talk to folks around here who do.

 

[sparkymiller]

Not sure about the rules there, but with the right ember protection only stove, I could imagine it looking nice if you cut a large sheet of steel in the shape of a “T” and inserted the leg of the T into the firebox (cut to fit) and had the wings of the T extend the width of the existing pad, and as deep as the new stove required.
It looks like the part that would need to extend forward would need a shim to level it. Maybe some hardy backer or an exact fit may need some strips ripped on a table saw to shim the difference from the existing pad to hardwood floor. Trim it in some rough cut or moulding to smooth the transition.

Another option is tile for ember protection, but I suspect there may be movement in different seasons and conditions between the wood floor and the pad. So just adding backer board to the wood to level it, then tiling the whole thing is likely going to crack across the union.

A small/medium free standing, rear vent stove with a steel extension and a block off in the chimney would get my vote for ease of installation. Just depends on how much you want to modify.

I'm liking the idea of a free-standing stove more and more! Thanks @30WCF !