Limestone fire pit keeps cracking

[HappyHome]

Hello, all.

Last fall, I built a 6' diameter by 18" high round firepit out of guillotined 5"x5" limestone blocks. The fire pit was intended to both be beautiful and functional. The stones are very evenly supported, sitting on a 6 foot square of 24"x24" concrete pavers, that sit on a 12" thick compacted gravel base. We have about 100 dead mature ash trees on our property, and have been using the fire pit to burn the waste left behind after limbing the dead trees we felled.

My problem is: the limestone keeps cracking down the middle, or "shards" of it keep flaking off the top row. Has anyone had this problem, and is there a way to modify the fire pit's design to avoid further damage? I'm considering a cinder block or cast iron inner ring so that the limestone doesn't absorb as much heat.

 

[bholler]

Hello, all.

Last fall, I built a 6' diameter by 18" high round firepit out of guillotined 5"x5" limestone blocks. The fire pit was intended to both be beautiful and functional. The stones are very evenly supported, sitting on a 6 foot square of 24"x24" concrete pavers, that sit on a 12" thick compacted gravel base. We have about 100 dead mature ash trees on our property, and have been using the fire pit to burn the waste left behind after limbing the dead trees we felled.

My problem is: the limestone keeps cracking down the middle, or "shards" of it keep flaking off the top row. Has anyone had this problem, and is there a way to modify the fire pit's design to avoid further damage? I'm considering a cinder block or cast iron inner ring so that the limestone doesn't absorb as much heat.

Yeah you need to protect that limestone. I would go with an inner metal ring. Cinder block will just crumble

 

[DAKSY]

Limestone is porous. It can have air pockets
& after a rainfall water can get into those pockets.
Both air & water EXPAND under heat.
Probably not an ideal refractory material.

 

[HappyHome]

Limestone is porous. It can have air pockets
& after a rainfall water can get into those pockets.
Both air & water EXPAND under heat.
Probably not an ideal refractory material.

I agree. Unfortunately it was the only material that stoneyards within 200 km of my home could get their hands on. After 4 months of trying, I figured it was limestone or nothing.

 

[DAKSY]

I think I would try lining it with fire brick.
Cheap enough & will withstand some very
extreme temps AND protect your limestone...

 

[Isaac Carlson]

I have yet to find something that can hold up to the temps I get with fires. Firebrick is the only thing that comes close.
That roxul board stuff works but it's fragile.