I Have a Cracked Fire Brick! What Should I Do?

I do not know what model my Harman fireplace insert is....The data plate is probably hidden behind the fireplace enclosure. I can tell you that the firebox in 5 bricks wide across the back and 3 1/2 bricks deep.
My middle rear brick has developed a crack in it. The crack, I'm sure, is all the way through the brick and separates the brick in two horizontally. The two brick halves are still flush together and will easily stay put cuz, luckily, the steel brick retainer tang that sticks down from the top of the box will continue to hold it in place.

Soooooo - leave 'er alone? What should I do? Is it bad?

Thanks for your input!

Hi Gary, I'd leave it alone, the bricks get weak after a season or two of hot burning. As long as the pieces are still in place no harm is done or can occur.

I'd change them all when the heating season is over.

Greg L

I get that a lot at the rear of my boiler. It is best to take care not to disturb it. You want it to stay in place because if it starts to move it may not be a clean break and if a small chunk is dislodged it will work down to the grate and jam it and/or break it if you are not careful. Pick up a few spares at the stove shop and next time it is down replace it. I replace all the brick every few years.
They usually don't do well by the draft input because of thermal shock, at least that's why I think my rear ones are always cracking. They don't last more than a year or two.

You can also get fireplace mortar or furnace cement and use that to bring it back together. I've done it and it works pretty good.

If the fire brick is just cracked, there are no missing pieces and the crack is essentially tight, there is not a need to do anything. It's a cosmetic problem only.

They are only a buck or two. I use a VERY heavy pry bar to poke my fire and I bust them up accidentally all the time. I have a few missing right now. I would like to replace them but every time I stick my hand in there to put the new one in I get burned and blistered badly !!!

I replace the firebrick at the start of every season with near pieces. And they still crack after a few months. ':x'

A local building supply house who would carry standard bricks and cinder block typically carry firebrick at half the price of those specialty stove stores. I'm stocked up through next year. .92 cents ea. for the narrow bricks. I think 1.72 ea for the large bricks.

I pull the old brick out and replace them with "Plastic refractory" It comes in a 55 pound block and you cut it with an ax and pound it in place. Smooth it out with a putty knife and you are all set. It is available from anyplace that repairs boilers. It comes in all price ranges but the cheapest is fine for stoves. I've used it for 30 years without complaint.

Cap wrote:I replace the firebrick at the start of every season with near pieces. And they still crack after a few months. ':x'

A local building supply house who would carry standard bricks and cinder block typically carry firebrick at half the price of those specialty stove stores. I'm stocked up through next year. .92 cents ea. for the narrow bricks. I think 1.72 ea for the large bricks.

That's insane. I pay $9.99 per brick when I buy them. I'm gonna gonna go by my building supply and see if they have any.

I'm On Fire wrote:That's insane. I pay $9.99 per brick when I buy them. I'm gonna gonna go by my building supply and see if they have any.

Go to a real brickyard, under $2.

I'm On Fire wrote:That's insane. I pay $9.99 per brick when I buy them. I'm gonna gonna go by my building supply and see if they have any.

Tractor supply sells them for $2.00 or $2.50, I forgot....

coaledsweat wrote:

I'm On Fire wrote:That's insane. I pay $9.99 per brick when I buy them. I'm gonna gonna go by my building supply and see if they have any.

Go to a real brickyard, under $2.

Tractor Supply carries standard grade firebrick too. Last week priced at $2.99 ea. Price certainly went up. I recall they had the bricks on sale last season for less tan $2 in the Oct time frame. Check the website each week for this years sale.

I get the impression that some people are replacing them every year or two just because??? I've seen firebrick that was 30 yrs old and still OK. The cracked one I would only replace if at started coming out. I might replace a cracked one during the summer, or if I was doing a total rebuild, but if it's cracked & solidly in place, it may well go for years and years.

Freddy wrote:I get the impression that some people are replacing them every year or two just because??? I've seen firebrick that was 30 yrs old and still OK. The cracked one I would only replace if at started coming out. I might replace a cracked one during the summer, or if I was doing a total rebuild, but if it's cracked & solidly in place, it may well go for years and years.

I agree Feddy, Unless it's falling out and even then only if I can't cement it back into place. A crack is nothing to worry about. As long as hot coals remain off the surface you are protecting, it's still serving it's function. I keep a small tub of furnace cement for patching up or "cementing" loose brick.

Freddy wrote:I get the impression that some people are replacing them every year or two just because??? I've seen firebrick that was 30 yrs old and still OK. The cracked one I would only replace if at started coming out. I might replace a cracked one during the summer, or if I was doing a total rebuild, but if it's cracked & solidly in place, it may well go for years and years.

Haven't replaced any on the DS yet. No reason, they are still clean. But on the wood stove I had I'd replace some of them every season. The main reason for that was I over fired the stove every winter so where the fire was hottest the brick would turn soft and crumble.