# Best type of concrete/morter to use for hearth?



## kwalters92 (Sep 17, 2015)

We recently bought a King 628A wood stove and are currently building a hearth for it. We installed cement board with 1 in ceramic spacers behind it for the floor and two walls. We are using sandstone for the walls and floor.

My question is: What type of mortar is best for building a hearth? The guys at Lowes pointed us in the direction of a fire safe mortar but the cost of that type is $87 per 40 lb bag...


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## begreen (Sep 17, 2015)

Welcome. What are the construction details for the hearth?

PS: Be sure to include the final height of the hearth before setting the wall shields. The bottom of the wall shield needs to be 1-3" above the top of the hearth so that air can freely convect behind the wall shield.


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## kwalters92 (Sep 17, 2015)

The hearth is being installed in the corner of the house. On top of the cement board we are putting rock on the floor and walls. The clearances we have are 16" all around.

What do you use to finish the gap between the floor hearth and the wall?


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## begreen (Sep 17, 2015)

Normally there is no finish on that gap. It's down low and almost disappears from view. You could extend the stone to the hearth like feet as long as there is a good sized 12-14" slot per stud cavity. For the hearth I would double up on the 1/2" Durock NexGen cement board sheets to increase insulation. Stone can be a good conductor of heat. IIRC the recommended hearth is bricks on edge or 4" thick brick which is R=.8. 

Also, put an inch or so of clean sand in the stove firebox bottom before firing.


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