Sand and Brick Hearth

[dannyh]

I am replacing the tile on my raised fireplace hearth. The hearth is 7" high, 70" long and 16" wide. The perimeter is surrounded by bricks, stacked 2 high.

When I removed the tile I found ~1" thick concrete on a layer of sand. Within the sand there were a few scattered bricks. I've removed the sand and brick and I'm left with an empty box. Tentatively, I've laid several more bricks level and filled sand in-between. I've placed a layer of wonderboard on top of the sand/brick and plan on placing self leveling concrete until flush with the top of the perimeter bricks.

Any suggestions for a better method?

 

[bholler]

I am replacing the tile on my raised fireplace hearth. The hearth is 7" high, 70" long and 16" wide. The perimeter is surrounded by bricks, stacked 2 high.

When I removed the tile I found ~1" thick concrete on a layer of sand. Within the sand there were a few scattered bricks. I've removed the sand and brick and I'm left with an empty box. Tentatively, I've laid several more bricks level and filled sand in-between. I've placed a layer of wonderboard on top of the sand/brick and plan on placing self leveling concrete until flush with the top of the perimeter bricks.

Any suggestions for a better method?

What is the hearth extension sitting on?

 

[dannyh]

What is the hearth extension sitting on?

Concrete. It is not a floor slab though so I’m not sure how thick it is since we are on the second floor of a duplex.

 

[bholler]

Concrete. It is not a floor slab though so I’m not sure how thick it is since we are on the second floor of a duplex.

Ahhh ok there should be no combustibles under that slab but in your situation even checking that would be difficult. I would say replace the sand with concrete that is pinned back to the slad under the hearth

 

[dannyh]

Ahhh ok there should be no combustibles under that slab but in your situation even checking that would be difficult. I would say replace the sand with concrete that is pinned back to the slad under the hearth

That's a lot of concrete and a huge headache if I ever need to remove the hearth. I think the sand provided two functions, one being a filler/base and the other was to allow expansion within the hearth. With concrete, any expansion would put stress on the whole hearth.

 

[bholler]

That's a lot of concrete and a huge headache if I ever need to remove the hearth. I think the sand provided two functions, one being a filler/base and the other was to allow expansion within the hearth. With concrete, any expansion would put stress on the whole hearth.

Yes but concrete is what code calls for

 

[dannyh]

Yes but concrete is what code calls for

Correct me if I'm wrong, and it may vary between standards, but do they not only call for min. 2" of non-combustible materials?

 

[Ashful]

Interesting. A few 18th century houses I’ve known have used sand in a framed box as the foundation for a hearth extension on second floor fireplaces, so it’s nothing new. But bholler knows his code, I just know history.

 

[Ashful]

Correct me if I'm wrong, and it may vary between standards, but do they not only call for min. 2" of non-combustible materials?

Some stoves require only ember protection, even sheet metal or glass over wood flooring can work, in those cases.

Are you keeping as an open hearth, or installing an insert?

 

[bholler]

Correct me if I'm wrong, and it may vary between standards, but do they not only call for min. 2" of non-combustible materials?

Yes it needs to be a minimum of 2" but also needs to be self-supporting with no combustibles contacting the bottom

 

[bholler]

Some stoves require only ember protection, even sheet metal or glass over wood flooring can work, in those cases.

Are you keeping as an open hearth, or installing an insert?

It is a woodburning fireplace by code the hearth extension needs to meet requirements for that even if a stove or insert is to be used.