Concrete Hearth

[griffin0601]

I wanted to replace the tile on my existing fireplace. I ended up removing all the concrete/mortar to make sure everything would come out even.

After removing the concrete from the hearth i found that there was no subfloor just this wire that you can see straight to the basement.( I have attached photos) should I put down a subfloor and then lay the concrete on top?

 

[bholler]

I wanted to replace the tile on my existing fireplace. I ended up removing all the concrete/mortar to make sure everything would come out even.

After removing the concrete from the hearth i found that there was no subfloor just this wire that you can see straight to the basement.( I have attached photos) should I put down a subfloor and then lay the concrete on top?

It was actually built correctly. You can either make wood forms under that mesh and bar that need to be removed after the concrete sets. Or you can make a sheet metal pan. But no subfloor ontop

 

[griffin0601]

It was actually built correctly. You can either make wood forms under that mesh and bar that need to be removed after the concrete sets. Or you can make a sheet metal pan. But no subfloor ontop

If I was to make the slab first and then put it in on top of the wiring. Would this be just as efficient as laying the concrete straight in the space.

 

[bholler]

If I was to make the slab first and then put it in on top of the wiring. Would this be just as efficient as laying the concrete straight in the space.

Nope. That mesh and rebar should be in the middle of the slab roughly

 

[Highbeam]

If anything, a little closer to the bottom than top. It's for tensile strength. Be sure your forms below are strong enough to hold the weight of the wet mud. Would be an awful mess if it fell down.

 

[bholler]

Yes what he said

 

[kennyp2339]

How long did that take you to chip out? just curious

 

[griffin0601]

If anything, a little closer to the bottom than top. It's for tensile strength. Be sure your forms below are strong enough to hold the weight of the wet mud. Would be an awful mess if it fell down.

Can you make any suggestions for the form to make it secure enough from below?

Also the concrete was not embedded in the wire that is currently left. My original plan was to make a level base. Put a new wire mat down and then lay the concrete.

 

[griffin0601]

How long did that take you to chip out? just curious

We have been working on this for quite a while on and off. From the tile about a week originally trying to not break the concrete. To the surround and then the final slab which took a day a piece. Turned into a bigger project then anticipated.

 

[Rearscreen]

An alternative would be to make the concrete slab similar to making a concrete countertop. Melamine form - tray - and pour the concrete into it. (Other steps and reinforcement in addition are needed) Once set, take off form and flip the concrete slab and put in place.

 

[begreen]

An alternative would be to make the concrete slab similar to making a concrete countertop. Melamine form - tray - and pour the concrete into it. (Other steps and reinforcement in addition are needed) Once set, take off form and flip the concrete slab and put in place.

Not sure if that would fly, The hearth is supposed to be integral with the inner hearth in the fireplace, no gap.

 

[bholler]

An alternative would be to make the concrete slab similar to making a concrete countertop. Melamine form - tray - and pour the concrete into it. (Other steps and reinforcement in addition are needed) Once set, take off form and flip the concrete slab and put in place.

That is not acceptable. The hearth extension slab needs to be tied into the hearth slab.

 

[Rearscreen]

That's why they invented concrete chalk or some type of grout. To fill that gap. You know, something fireproof. Something to prevent embers from going below. Obviously, you wouldn't leave a gap. That wouldn't be smart.

 

[bholler]

That's why they invented concrete chalk or some type of grout. To fill that gap. You know, something fireproof. Something to prevent embers from going below. Obviously, you wouldn't leave a gap. That wouldn't be smart.

But unless they are tied together it will just crack. Which is why code doesn't allow you to do it the way you suggested.

 

[kaitlynloza]

How to Replace a Hearth with Slate Tile

Ask This Old House mason Mark McCullough replaces a common terra cotta hearth with slate tile.

www.thisoldhouse.com

I watched this video and there's a part where they go in the basement and you can see the support that is to be removed after the hearth sets. It explains it as well. Hope this helps!