Used firebricks ok to use?

I was able to obtain a fairly large quantity of used firebrick. Most are in good condition. I am wondering if I should use them on the floor of the hearth. I’m sure I would soak them and clean them thoroughly. Has anyone used ok’d firebricks for a hearth before?

Hi Gerald and welcome to the BrickWood forum!

Sounds like you are well underway with your build.

I’m always happy to see people thinking about making sure building materials stay out of the landfill. But I’m not sure I’d want to put used firebrick into the hearth for a couple of reasons:

The hearth takes direct fire and needs to refract heat energy
The hearth comes in direct contact with food

If and only if you are absolutely certain of both the grade of the bricks (low or medium duty firebrick), and you are absolutely sure of their previous use, you could use them.

Otherwise, it’s not worth it. One scenario is one or more bricks cracking under fire. While the brickwood hearth design does allow you to pluck most bricks out and replace them, I can testify that it’s a “procedure.” And, if they are contaminated, even a good soak might not be enough to leach contaminants out.

Hope this helps, and keep us posted on your build.

1 Like

Thanks for your reply. I was coming to the same conclusion. I think I will use new block for the hearth.
Is there any way to test the other brick to use in the rest of the oven? I know they came from a smoke stack from a foundry and they are about 75 years old.
I agree that it wouldn’t be worth it if they are likely to fail.

1 Like

Personally I wouldn’t use them. There were some pretty nasty chemicals used in industry 75 years ago (e.g. lead, chromium, etc) that I wouldn’t want around my food.

There is a way to test them to determine chemical make up but it would probably cost more than buying new bricks.


I think that’s your answer, Gerald. I’d stay away from them for this reason:

(thanks Ken!)

But another reason is that they likely to be a different “grade” of brick than the ones you need. A foundry generates super-hot temperatures, which casually sounds like “over-speccing” your oven materials, but a high duty or super duty brick will take much longer to absorb and then start radiating heat back into your oven.

I think you’re better off getting a pallet of 200 firebrick from a known source and of a known grade.

Good luck with your build, Gerald!

1 Like

Thanks for your replies. I spoke to a local lab and they said that they probably don’t have toxic chemicals due to the fact that they are firebricks. However they could have asbestos which is a $20 test. You bring up a good point about heat issue.
In that regard would it be advisable to use thinner brick on the hearth so it would heat up quicker. There is little difference in price.

This is a good article about used firebricks.

Thanks again.

I am still in construction. Jeez, big job!
I bought used kiln brick, then realized that the kiln could have used for unhealthy materials. Now I have a bunch of those bad bricks. Trying to think of a new use?
I found a source for old unused FB from a kiln. Mayb1930-1950 curved bricks. A real pain to work with, but I am committed…or should be!

Welcome to the BrickWood forum!

So, you’ve probably got high or super duty brick there, and it’s curved to fit the profile of a round foundry kiln.

If you have not acquired them, I’d say leave them alone. There’s nothing wrong with them for their intended purpose. But anything above medium duty is going to present two issues: extremely hard to cut, and they will heat up and refract more slowly because they’re engineered for much higher temperatures than your application. The curves make it a non-starter just for base construction reasons.

As for the used brick, why not use them to line a fire pit or similar project?

I would avoid high or super duty brick in any case, used or new; and these throw an extra curve at you.