I want to put a small fire pit (3ft x 3ft) into backyard. I checked the stone options at home depot & lowes and just the material will cost around $250.

I was thinking about building a mold and pouring concrete into it instead of using stone. Cost would be less than $50 in this case.

Is it ok to use concrete instead stone in terms of high heat and fire? Should I put some sort of heat shield inside of the fire pit to protect the concrete?


After the suggestions made by @BobOClockand, and @Ecnerwal I decided to go with blocks (got from Lowe's and they are fire resistant) to the bottom I put lava rocks. I checked the outside surface of the blocks for temperature after a while and they were relatively cold, so I will cover the outside with natural stone for better looking.


I put lots of wood into fire pit for one last final test kept it burning for 4-5 hours. The heat was very intense and when I checked the next day, almost all the blocks were cracked.

Conclusion: Even fire resistant blocks need fire insulation with firebrick. I will replace the blocks and add firebricks inside.

  • The stuff Lowes sold you was not real fire brick . Probably someplace in the info it says "fire resistant". Commented Sep 26, 2019 at 18:01
  • yes, I learned the lesson from the hard way.. the blocks just cracked under the heat. Commented Sep 26, 2019 at 22:12

2 Answers 2


You should line it with firebrick or (since you like molding and casting things) castable refractory. Edit: on second thought, stick to hard firebrick - most castable does not like to get wet. Regular concrete is prone to spalling & cracking in direct fire exposure.

Depending on the shape of the "pit" a 2" layer of sand can work, if it will stay put (ie, if the "pit" is rather shallow)


Concrete blocks should NEVER be used for firepits. They can explode and cause serious injury and/or death. Always use firebrick or cinderblock for fire pits.

  • Welcome to DIY.SE! Do you have a source you can link about exploding concrete blocks?
    – mmathis
    Commented Apr 11, 2017 at 16:55
  • I've personally observed an explosion caused by building a campfire on a driveway. Air pocket in the concrete just heated up and went boom. Flaming logs went everywhere - it was a miracle nobody was hurt. Google "concrete explode fire" or something similar and you'll get plenty of info. Commented May 8, 2018 at 15:11
  • In our lab castables ( fire resistant concretes) were evaluated. One test was to determine how long they needed to cure before being heated. To do that , samples were put in a furnace and it was heated . It was not unusual for samples to explode ( from steam) and even shake the furnace door ( which had heavy steel latches.) Commented Sep 26, 2019 at 17:58

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