Replacing Heatform with insert, and demo/remodeling stone

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Jeff15

Member
Dec 9, 2020
25
Tahoe
I have a Montlake 300 on order that I want to install into my 70s house that has a heat form (I'm pretty sure), along with demo'ing the existing green rock fascia and remodeling with something else. I need to have this installed for winter!

I started happily demo'ing the green rock above the firebox, then paused for fear of loading bearing concerns around the heat form. I understand most people just cut out the damper and the backside to make enough room for the liner, but since I'm remodeling the whole fireplace anyway, and I want to add things like electric (for the fan) and Auber flue temp sensor, I might as well rip it all out...

Some facts
  • Mid 70s house in Douglas County, NV
  • Masonry/brick (upstairs), large stone/rocks (downstairs), and cement blocks make up the chimney
  • 4 flue chimney, with terra-cotta liners in each. Upstairs open fireplace (heat form) on one side, and small Morso stove (no liner) on other side. Downstairs open fireplace (heat form with a gas line - I've capped off the gas) on one side, outdoor BBQ/smoker insert on the other side
  • 3" drop from the hearth into the firebox (b/c of gas line)

Rough goals / plan
  • Demo all the downstairs green rock, keeping the upstairs brick, open fireplace, and small stove as-is
  • Remove heat form, or cut out what is needed (leaning towards removal, to make electric outlet, Auber sensors, etc easier)
  • Install Montlake 300 with insulated flexible dual wall liner, roxul, back off plate, etc
  • Remodeling of fireplace will likely have to wait til next Spring/Summer
I'm pretty much ripping the house down to studs, adding a garage addition, renovating, etc, so I want to do this fireplace right.


Appreciate your advice.

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Last edited:

bholler

Chimney sweep
Staff member
Jan 14, 2014
31,053
central pa
I have a Montlake 300 on order that I want to install into my 70s house that has a heat form (I'm pretty sure), along with demo'ing the existing green rock fascia and remodeling with something else. I need to have this installed for winter!

I started happily demo'ing the green rock above the firebox, then paused for fear of loading bearing concerns around the heat form. I understand most people just cut out the damper and the backside to make enough room for the liner, but since I'm remodeling the whole fireplace anyway, and I want to add things like electric (for the fan) and Auber flue temp sensor, I might as well rip it all out...

Some facts
  • Mid 70s house in Douglas County, NV
  • Masonry/brick (upstairs), large stone/rocks (downstairs), and cement blocks make up the chimney
  • 4 flue chimney, with terra-cotta liners in each. Upstairs open fireplace (heat form) on one side, and small Morso stove (no liner) on other side. Downstairs open fireplace (heat form with a gas line - I've capped off the gas) on one side, outdoor BBQ/smoker insert on the other side
  • 3" drop from the hearth into the firebox (b/c of gas line)

Rough goals / plan
  • Demo all the downstairs green rock, keeping the upstairs brick, open fireplace, and small stove as-is
  • Remove heat form, or cut out what is needed (leaning towards removal, to make electric outlet, Auber sensors, etc easier)
  • Install Montlake 300 with insulated flexible dual wall liner, roxul, back off plate, etc
  • Remodeling of fireplace will likely have to wait til next Spring/Summer
I'm pretty much ripping the house down to studs, adding a garage addition, renovating, etc, so I want to do this fireplace right.


Appreciate your advice.

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There is absolutely no reason at all to remove the whole heat form. And even if you do there is no reason to demo the masonry
 

Jeff15

Member
Dec 9, 2020
25
Tahoe
There is absolutely no reason at all to remove the whole heat form. And even if you do there is no reason to demo the masonry
OK, I understand not needing to remove the heat form, I will plasma cut out the needed areas.
The reason to demo the stonework is to remodel it to a different kind of rock... but I will just do what's necessary to install the new insert for now and consider the remodel next year.