Avoid heat cracks in cast iron in the fireplace?

[David]

Temporary cracks can sometimes occur in the plaster around the cast iron supports when using an open fireplace. Any tips on how to avoid it? Alternative materials or minimum distance to open fire? All tips are welcome.

Best regards,
David

 

[Fasting65]

How about eliminating the support steel by making a reinforced concrete beam instead?

I understand what you're aiming for and am thinking a bit myself since we are going to build a stove that requires support using steel or a concrete beam. Hope someone has a good answer.