Remove rotted steel firebox or can it support a wood stove insert?

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New Member
Sep 29, 2023
San Francisco, CA
Hi everyone. I have a house that was built in MA in 1978 and renovated in 2011 with the exception of the fireplace. We purchased our home in 2020 and I don’t know much about the fireplace or when it was last used. We have a three flue chimney with one flue decommissioned that was used for a broiler, the middle flue that has a rotted steel firebox fireplace, and the third flue is a wood stove in the basement. Nothing is in use currently. I would really like to install a wood stove insert or repair the firebox in the fireplace and am considering my options. I don’t know much about the firebox other than it is steel and could be a heatilator…

I could be wrong on all of this, but it looks like there was once vents in the brick similar to a heatilator (the pic without paint on the bricks is from when the house was sold to the owners before me), and at some point they covered them up and painted the brick (by the owners I bought the house from). I don’t know if they did anything beyond paint in order to use the fireplace or if it's been out of commission for a long time. There is not an ash box in the basement or outside, so I imagine this is the original firebox when the house was built. The chimney is not in bad shape.

At this point (almost 4 years later) I am tired of looking at this old box! I would be happy with whatever is safest and I want to do it right. I’ve been told different things from different sweeps - either the steel box needs to come out before a wood stove insert can go in, or it needs to stay because it is structural and the wood stove is contained and will be fine with the liner. Rebuilding brick is more effort than it's worth (I've been told). The steel box it completely rotted, so it can’t be supporting anything very well. So I’m at an impasse. If we start to take it out, I’d like to know what we’re getting into first and if it’s even necessary. I’d like the thing out but what’s that require? Can we do it ourselves?

There’s also the option of which wood stove insert could work here? I like the larger ones (it is a large room with kitchen/living/dining) because the breast wall is quite large in relation to the size of the firebox. The firebox opening itself is small so we would need a small insert, but how much of the breast wall is actually required structurally? Can we cut out some of the surrounding brick to accommodate a larger stove?

I received an estimate from a sweep for a wood stove insert into the rotted steel box (the one who said it's structural and must stay) with the following items:

  • Install a stainless steel woodstove liner, 6” elbow and adapter, top plate and cap kit
  • Stainless steel cap for top of chimney and cement crown
  • Cut out some brick and replace, remove moss and water seal spray
I am hesitant because it was a free estimate and they didn’t do a very thorough inspection to really know if the weight of the insert can be supported by the floor of the rotted box. They also didn't offer guidance on size of an insert.
I don’t know what’s under there or what’s behind there, and you can’t see much without removing the box.

Any insight or recommendations would be appreciated! I am open to any thing (even a gas insert if that makes sense!).

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The sweep's free advice is correct. The safest and easiest solution may be to install a wood burning insert in the metal fireplace with an insulated 6" liner. The floor can be built up with cement board once the debris is removed.

Once any water intrusion has been taken care of at the crown, it should be safe and without issue. The chimney is not tall so look at inserts that fit and will work on a 13' liner. Typically, these are inserts from Osburn, Regency, Pacific Energy.