Cut out heatform myself?

[Tjm]

So I talked to local blaze king dealer and it sounds like they’re comfortable cutting the smoke shelf out of my heatform to allow for a rigid insulated liner and fitting an ashford 25 ( mind you this is over the phone so far)
They said they would discount the install if I did the cutting myself. On one hand I’d prefer them do the cutting so they’re responsible for the result but it seems pretty strait forward and I’m an engineer with a cheap plasma cutter in the garage...I think they would do it like the borrowed picture below but I would prob square it up and bend in some tabs from the old material and then close it back in with a new piece like the sketch below. Prob could glue it in with gasket cement and but some stainless screws in it or even weld it in.
Let them handle it in case something goes wrong or wing it myself?

 

[mellow]

It isn't rocket science, even if you cut it wrong its hidden and will be covered with an insulated block off plate right?

 

[bholler]

So I talked to local blaze king dealer and it sounds like they’re comfortable cutting the smoke shelf out of my heatform to allow for a rigid insulated liner and fitting an ashford 25 ( mind you this is over the phone so far)
They said they would discount the install if I did the cutting myself. On one hand I’d prefer them do the cutting so they’re responsible for the result but it seems pretty strait forward and I’m an engineer with a cheap plasma cutter in the garage...I think they would do it like the borrowed picture below but I would prob square it up and bend in some tabs from the old material and then close it back in with a new piece like the sketch below. Prob could glue it in with gasket cement and but some stainless screws in it or even weld it in.
Let them handle it in case something goes wrong or wing it myself?
View attachment 276494View attachment 276496 View attachment 276495

It is a pain to do but not complicated I personally wouldn't use a plasma cutter just a grinder and sawzall. There is bound to be some crap on the smoke shelf which will smoke like hell filling the house if you use the plasma cutter.

Also why a rigid liner??? There really isn't any benifit over heavy flex

 

[Tjm]

Rigid insulated liner- just what the dealer suggested . Don’t think it costs any more really? Sounds more robust to me??? Does seem weird to me especially on an interior fireplace that the 1/2” of insulation makes much of a difference.
I’ve already had my hands up there and shoved my phone up with the video rolling. There’s about an inch of crap on the smoke shelf lol.
Ended up calling the town engineer who referred me to the fire Marshall. He basically said it’s my call/my house if I’m comfortable with it but at the end of the day if it was his place he would still let the dealer do it so that the whole job is on them if anything goes wrong. He said cutting out the shelf and leaving it open is fine with today’s inserts. the whole 8” vs 10” block before a combustible wall etc isn’t really an issue anymore with how inserts are designed to be contained.

 

[begreen]

A sawzall and grinder would be my weapons of choice too. Wear eye protection and a good mask.
A guess is they might be installing DuraLiner.

 

[Hogwildz]

Been there, done that. Super dirty job, but not too hard. Just good workout on the arms & shoulders. Sawzaw with construction or emergency blades, and a 4" angle grinder with carborundum blades. Get to it!


Nice sample photo, looks familiar ;-)

Personally I like the rigid liner. Pre-insulated, easy to install, easy to clean, and flows great.

 

[Tjm]

From your first few pics it looks like you did fill in the cut section?

 

[Hogwildz]

From your first few pics it looks like you did fill in the cut section?

Nope, cut it out, no fill in, installed liner: 5' flex at bottom, double wall insulated rigid the rest of the way. No need for any filling in, just install a block off plate and done

 

[Hogwildz]

Do yourself a favor, buy a painter's sock at the local hardware store to wear over your head and part of your face, use chitty clothes, and good eye protection. A respirator also. It is very, very dirty. I only used the eye protection, but wished I used the rest. You can use a shop vac to clean the smoke shelf out.

 

[Tjm]

When you say block off plate you mean up past the smoke shelf and not over what you cut right? Must be the angle that makes it looks like you finished off the cut area.
My dealer said they just stuff it with insulation as a “block off.” Should I insist they put an actual plate?
My smoke shelf goes 2” deeper than the vertical back of the inner wall. That must be where the Hollow chamber behind ends.

 

[Hogwildz]

When you say block off plate you mean up past the smoke shelf and not over what you cut right? Must be the angle that makes it looks like you finished off the cut area.
My dealer said they just stuff it with insulation as a “block off.” Should I insist they put an actual plate?
My smoke shelf goes 2” deeper than the vertical back of the inner wall. That must be where the Hollow chamber behind ends.
View attachment 276505

The block off plate can go anywhere between the lintel & the old damper area of the old firebox, which is anywhere under the cut out area. I installed mine just above the lintel as that was easiest to get into to work on for me. I fabbed and installed after the insert was installed. Not much room to work at that point, I also made it in 3 pcs. I suggest against just stuffing insulation up there, insulation does not stop airflow, and you want as much heated air as possible going out into the interior of the home, rather than up the old flue. Insulation on top of the block off is a good idea though.
I suggest trying to fab & install prior to insert installation to save much grief.

 

[bholler]

Rigid insulated liner- just what the dealer suggested . Don’t think it costs any more really? Sounds more robust to me??? Does seem weird to me especially on an interior fireplace that the 1/2” of insulation makes much of a difference.
I’ve already had my hands up there and shoved my phone up with the video rolling. There’s about an inch of crap on the smoke shelf lol.
Ended up calling the town engineer who referred me to the fire Marshall. He basically said it’s my call/my house if I’m comfortable with it but at the end of the day if it was his place he would still let the dealer do it so that the whole job is on them if anything goes wrong. He said cutting out the shelf and leaving it open is fine with today’s inserts. the whole 8” vs 10” block before a combustible wall etc isn’t really an issue anymore with how inserts are designed to be contained.

It is really really scary that a fire marshal said that.

 

[Hogwildz]

It is really really scary that a fire marshal said that.

Sounds like the cops & fires folks around here. They don't want to be bothered by anyone.

 

[bholler]

If you notch the shelf you need to either close it off or close off the vents. If you don't the blockoff plate is useless because you still have a big open space for air flow. If it is on an exterior wall I like to fill the cavity with rockwool to keep more of the heat in the house.

 

[Hogwildz]

If you notch the shelf you need to either close it off or close off the vents. If you don't the blockoff plate is useless because you still have a big open space for air flow. If it is on an exterior wall I like to fill the cavity with rockwool to keep more of the heat in the house.

Mine is closed off from the vents, but vents left open, and they actually still function.

 

[bholler]

Mine is closed off from the vents, but vents left open, and they actually still function.

Yeah how ever you do it you need to keep the air going through the vents from going out that hole you cut

 

[Tjm]

I was thinking of asking the installer to maybe throw a few thicknesses of roxul in there. I was wondering about fire/ heat resistance of what’s behind the chimney. It’s an interior chimney but I don’t know how thick the brick is on the backside. Sounds like you’re more concerned with airflow. The heatform is vented to the room behind but what’s the concern about air flowing if it’s got a liner? Just the cold drafts? CO?
I was first thinking of fabbing a plate and screwing/cementing it back in over the notch but now wondering if heat cycling could shear the screws in time.
I feel like all the examples I’ve found or people doing it cut a big hole and call it a day.

 

[Tjm]

Started cutting! I was able to clean (what I thought was) most of the build up off the smoke shelf and gave the plasma cutter a shot. It worked really well for the inner shell up to the damper. That’s about where I am right now. Plasma cutter doesn’t like cutting up side down, I broke my grinding wheel, and the metal blades I have for the reciprocal saw are too short.
Turns out the smoke shelf itself is two layers of steel. Seems like they start together at the damper flange and the gap grows as it goes toward the back of the fireplace. That’s complicating things a little. Anyone see this before? You can kinda see it in my past pic where the plasma cutter pierced the first sheet but not the second.

 

[Tjm]

I really want to put a steel chase up the cutout but im starting to consider calling it a day and letting the installer finish himself. But I think he will just put a couple of inches of insulation up the back and leave it open. This is an interior chimney and I THINK I have 6” block behind the heatform with furring strips and knotty pine In my laundry room behind it. Two upper and lower vents from the heatform go to the laundry room behind as well. I’ll probably try and get a bette sawzall blade and see if that does the trick then leave it to the installer.

 

[Tjm]

Smoke shelf is not two layers…. It was the darn damper flipped back. I figured it was removed but they just flipped it inward. Now I gotta figure out how to get that out…

 

[begreen]

Thanks for clarifying. I was wondering what was going on there.

 

[Hogwildz]

Man you came quite a ways down the back.

 

[Tjm]

It was easy cutting and by the time you add the necessary 30 degree elbow on the stove collar, it will be flush with the back of the stove. Elbow will be higher but that made it so my patch panel will be vertical and simpler shape. Gives me 1.5” clearance to the liner. Think it’s a problem? Attached 1/2 scale section.

 

[MEngineer24]

It was easy cutting and by the time you add the necessary 30 degree elbow on the stove collar, it will be flush with the back of the stove. Elbow will be higher but that made it so my patch panel will be vertical and simpler shape. Gives me 1.5” clearance to the liner. Think it’s a problem? Attached 1/2 scale section.

View attachment 283099

Made any more progress on your project?

 

[Tjm]

Not yet… Chimney was tarped off for rain after they poured the crown and I realized in a hurry without the draft sucking out the dust it was even more dirty than before! Got some nice sawzall blades to try. Hopefully later today. Also probably going to grab my pneumatic 3” cutoff tool or body saw back from my buddy to do the back side-to-side cut.