Q&A: crack in fireplace insert. what can i use to repair it?

Question by atom631: crack in fireplace insert. what can i use to repair it?
i have a fireplace insert in my house. i am uncertain of exactly what is it made of, but it definitely isn’t brick (although it looks like brick). I think they are called firebricks, but it is one full sheet and has seams where the sides meet.

i noticed that i developed a crack that runs vertically down the back wall of the insert. it is about 1/4″ to 1/2″ wide and runs for a good 12″-14″ (pretty much the entire length of the insert). when cool, i pressed my fire poker against it, just to see if it flexed or not…and it certainly did.

i went to home depot and i dont think they understood exactly what i have b/c they recommended for me to use one of the following 3:

PL: concrete crack and masonry sealant

Bondo: concrete, brick and stucco repair compound

Pre-mixed concrete patch.

I don’t think any of these are a proper solution b/c none of them say anything about being rated for high-heat. how can i go about repairing this or do i have to replace the entire insert? should i call in a pro or is this a DIY project with the proper material?

Best answer:

Answer by xenon
How wise of you not accepting any of these products, you require “fireclay repair putty ” comes in a sealed can and is applied with a small trowel or broad bladed knife, Allow to dry before lighting a fire.
Depending on where you live it is sold under different names, but they are always the same formulation.

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6 Responses to “Q&A: crack in fireplace insert. what can i use to repair it?”

  1. steveko777 says:

    Xenon is correct–and most guys in Home Depot dont know what they are talking about. Try to find an Ace Hardware or other smaller store and they may have or order it

  2. Richard S says:

    “Xenon”is why ahead of your local stores! All that they suggested would not withstand the heat. I repaired a lined wood furnace using a dry, cement-like powder which was mixed with water and forced into the crack. (My “fire bricks” were not shaped like bricks: They were approx. 8″ x 12″ x 1 1/4″ thick, tan in color.) ‘Found the product through a stove/fireplace store. It was much more expensive than cement… but, you don’t use much.
    The repair cracked out very quickly. Too brittle (?) and couldn’t stand the shifting and banging when I loaded the firebox?
    Next I tried making a crude form inside the firebox and pouring the repair material to cast a liner. Great idea. It, too, failed all-too promptly!
    So, no real wisdom here. Could you get a heavy metal plate fitted to the back of the fireplace and install it to serve both as protection for the cracked surface and a reflector to bounce heat into the room?

  3. William B says:

    what you need is retort cement its made for high heat, used in furnaces
    fill the crack let it dry then make a small fire [real small] dry it for 2 hrs

  4. Dan the brick man says:

    although there is probably nothing but more masonry behind it, i would go to a stove dealer and get some ceramic insulation( brand name is kaowool) stuff the crack with the wool and spread some fire clay over the crack as a patch…we repair big kilns using a product called castable but dont think the average stove place would have it…that would be the ideal patch…

  5. richard says:

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