Replacing bricks, is the firebox a structural part of the fireplace?

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

nate0918

New Member
Sep 24, 2021
47
Keizer, Oregon
Well, after 15 years I finally was able to get a home that included a wood fireplace, one of our "must haves". That being said, the two fireplaces in the home need some maintenance and I've always wondered about the bricks used for the firebox. I have several that need replaced. Now with ignorant question #1, are the firebox bricks a structural load-bearing component of the chimney? If I remove several of them, am I compromising the structure? I have had the chimneys inspected and was told that all was good with the exception of the maintenance on the firebox and eventually the flashing at the roof will need to be replaced. I will post some pics when I get home today but was curious on the structural part. The house was built in 1950 if that helps date the construction method. I will be hiring a chimney sweep to clean the flues but I was going to attempt the brick repair myself. I'm sure that I am not asking all the right questions right now but I'm learning as I go. Any advice is greatly appreciated!
 

stoveliker

Minister of Fire
Nov 17, 2019
5,224
Long Island NY
Maybe post a pic of what you are talking about? There are chimney specialists here. I hope they'll respond.

However, I think that the bricks directly in contact with the fire may not be structural, because thermal resistance and load bearing requirements are a bit opposite: the first often are lighter bricks with many tiny voids, and that does not do well under compression (load).

I Amy be wrong though.

However, for a fireplace, you do need (I think) two layers of brick to be up to code. So taking one out may make it unsafe.

Regardless, a fireplace is a big hole where warm air gets sucked out of your room. Why not put a stove or insert in there. Flame show too, but also better heating (power outages...), and much less heat loss when not in use (doors closed).
 

nate0918

New Member
Sep 24, 2021
47
Keizer, Oregon
Here are a couple pics of what I am referring to. There are several bricks in the back of the fireplace that are damaged. Replacing them seems easy enough but just tearing them all out makes me question if I'm weakening the chimney structure. I have a central natural gas furnace so I'm not worried about actually heating the house, the fire place is more for family gatherings, fun, and have look and feel of real wood fire.

654450519.jpg 654450193.jpg
 

armanidog

Feeling the Heat
Jan 8, 2017
402
Northeast Georgia
First, do you have a cap on the chimney? An open chimney will let water drip onto the smoke shelf and then the water will seep in behind the brick and cause deterioration of the mortar and bricks.
You can remove some bricks from the firebox walls without worrying about the integrity of the chimney. They are expensive but firebrick would help prevent future cracks if the fire gets too hot.
You can use an angle grinder with a diamond wheel to cut out the damaged brick. You will have a cloud of dust so make a tent of plastic to control the dust. A very fine filter in a shop vac will be needed. Goggles, respirator, and heavy gloves also needed.
If you have any cracked or deteriorating mortar joints cut them down by a half inch. I suggest furnace cement to repoint the brick and bed new brick. .
 

EbS-P

Minister of Fire
Jan 19, 2019
3,003
SE North Carolina
The firebrick replacement can be a diy project. Have you lit a fire in this fireplace? Judging by the smoke stains it seems to have been well used. Ask the sweep for an inspection. It’s worth the cost to know what shape it’s in. If the bricks are in bad shape what else could be? We went down a similar path but the amount of smoke that spilled into the house made me cough for days after and it just wasn’t worth it. We used alcohol burners for several years. Then went with a wood stove. If I were to burn more than 30-40 loads realistically that’s like 10-15 fires a year I would consider an insert. (Your flue inspection make find issues that require addressing and after a liner you are 2/3 of the cost to an insert).

I tried to reset my top course of firebrick after I removed my damper and it did not go as well as I thought it would. It’s fine. Job is done but if I had to look at my hack job everyday it would bug me. The high temp mortar needs to be fired to cure within a certain amount of time.

Just some thoughts.
 

nate0918

New Member
Sep 24, 2021
47
Keizer, Oregon
Thank you for the replies, this is all good to know. I'll tackle the bricks after the chimney sweep cleans and inspects everything so I can make sure there isn't anything else that needs to be addressed and possibly need work that I can't take care of. I do not have a chimney cap. This is on the growing fixit list in my new-to-me house. There are actually two flues in the fireplace. The pics are from the fireplace in the basement while a second fireplace is directly above it in the living room, where the brick looks in a lot better shape. So to summarize, the bricks in the firebox are not structural, awesome.
 
  • Like
Reactions: armanidog