Thread: Cultured stone fireplace clearance to fire box

Anyone know what the requirements are for clearances to a fire place for cultured stone?

Mr. Ramsey,
This is taken from "Centurion Stone" website;

Question: Is there a fire rating on Centurion Stone?
Answer: Testing show no signs of product supporting or contributing to flame spread, combustion or smoke development.

Question: Can Centurion Stone be used on a fireplace front?
Answer: Yes, but not in the fire box area.

Question: Can Centurion Stone be used behind a wood burning stove?
Answer: Yes. The stove manufacturer clearances for combustible wall dimensions must be maintained.

Based on this, I would say treat all cultured stone or manufactured stone veneer same as combustible surface, minimum clearances apply.

Manufactured stone is a masonry material (concrete) so it should behave similar to other masonry materials. What would be important to consider is what is behind the manufactured stone. If a combustible material is behind the stone then that would control the required clearance, assuming there is not a ventilated airspace as specified in codes for applications like wood-stove surrounds.

I would ask them if they have a test report stating their product has passed ASTM E-136 as being "non-combustible". It may have a flame spread of zero but fall apart under this test as Wonderboard does.

Yes, the substrate is often combustible and a real problem.

On factory built fireplaces, check with the listed instructions as most require non-comb. material only over the header and not the sides. A good rule of thumb is never, NEVER allow combustible construction to lap over the black metal of a factory built fireplace.

I assume you are referring cast stone products which are made of concrete, which are allowed anywhere other masonry materials can be used, except for inside of the hearth area, where only firebrick can be used.

If you are talking about cultured marble, which is usually polymer-based, it must follow the code or installation manual for clearance to combustible materials.

By the way, most manufactured fireplaces allow (and recommend) covering all of the exposed flat, un-louvered sheet metal on the fireplace face with non-combustible materials for a more realistic finished product.

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