Worried about fireplace build. Please help

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midfiman

New Member
Sep 23, 2019
10
N/A
Hello everyone. I'm a homeowner currently redoing my family room, which contains an old 80s still red brick fireplace. A mason friend who has done some exterior stone walls, steps and front door landing/steps for me has offered to help (really do it, I'm just assisting in the heavy labor) to cover the existing brick fireplace (natural, untreated/not painted/not sealed) with natural (field?) stone that we bought by a pallet from a local distributor. The pallet consist of beautiful stones that are rectangular in shape, ranging in size of course. He cut all the stones down to have a depth of approx. 2.5 inches or so do reduce the overall weight, so stones range from say, 2"x6" face to 3"x 12" face, all with an approx. 2.5" depth. We are also changing it from a fireplace that is approx. 5ft high to one that spans the entire height of the room (9ft). We built a box out of 2x4s covered in 3/4" plywood, that will be covered with black membrane and then wire lath attached to it to mortar onto. He has started to build the bases on both sides of the fireplace opening, with approx. 2" of cement behind the stones (and just a little in between as to not see it from the front) and will build up from there.

My points of concern are as follows:

-The cement he is using is comprised of Portland cement and sand and water. He said this is super strong and strength/adhesion will be no problem. I worry about how well this will stick to the existing brick, as well as how well it will still to what seems like a seemingly smooth surface of the stone (since all the backs have been cut).

-He says the majority of the weight will rest on the bases as the entire "wall" will rest on these bases. However, the fireplace opening is a concern for me. He thinks that the cement he is using will be strong enough to adhere to the brick and that bond will be strong enough to hold up the stones over the top of the opening (there is no transfer of weight to the sides here). If you can imagine approx. 7 ft of stone on top of this opening, that's got to be hundreds of pounds, if not a thousand or more, etc. Should I think about adding a lintel(?) or some kind of iron rod that goes across the bottom of the part on top of the fireplace opening that would basically transfer weight to the side supports, or some kind of metal supports that can be drilled and inserted into the existing brick? This one worries me quite a bit.

-On the plywood part, like I said above, there will be a metal lath attached to the plywood and then the stones will be attached via the Portland cement mixture to this lath. Is that enough? Will this be strong enough to hold up these heavy stones?

My mason has been doing masonry work for 30 years and he has done hundreds of large outside jobs, etc and has also done many many jobs of stone veneer. He has admitantly only done a handful of fireplace jobs and since this isn't really a veneer and is MUCH heavier, I just want to make sure the method described above seems sound... ...or not.

This is our family room, and there are children playing, etc. Last thing I need to worry about is a stone falling out from 8 ft up, as some of these weight 10lbs, or worse yet, the entire thing crashing down.

Thanks in advance for your help.
 

midfiman

New Member
Sep 23, 2019
10
N/A
Here is a picture of the fireplace after tearing out some protruding bricks in the top rows and adding in the plywood/stud box on top for the top half.
 

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webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
Can you share a picture of the fireplace without the stuff in front of it?
 

midfiman

New Member
Sep 23, 2019
10
N/A
Hello, sure, here are a few more pics which will help hopefully. I was thinking about building up the two sides up to the level of the top of the firebox, then embedding a steel angle, maybe 4" high, 4" wide and maybe 1/4" thick, or something like that, into the cement, and having the first row of stones on top of the firebox sit on top of that angle. I would imagine that would be pretty strong and between being attached to the bricks and that metal angle holding the weight, it would be strong enough...?
 

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webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
Sounds like a good plan.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,106
central pa
Hello, sure, here are a few more pics which will help hopefully. I was thinking about building up the two sides up to the level of the top of the firebox, then embedding a steel angle, maybe 4" high, 4" wide and maybe 1/4" thick, or something like that, into the cement, and having the first row of stones on top of the firebox sit on top of that angle. I would imagine that would be pretty strong and between being attached to the bricks and that metal angle holding the weight, it would be strong enough...?
Just be sure to use lots of wall ties to tie the face to the structure. Typically I would have removed the brick face first before refacing. It could cause problems if you want to put an insert in there.
 
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Ashful

Minister of Fire
Mar 7, 2012
15,717
Philadelphia
Just be sure to use lots of wall ties to tie the face to the structure. Typically I would have removed the brick face first before refacing. It could cause problems if you want to put an insert in there.

I second the wall ties. Hopefully brick face is already wall tied to structure behind.
 

midfiman

New Member
Sep 23, 2019
10
N/A
Dumb question... ...where would I be putting the wall ties and how. Am I attaching wall ties to the bricks and encasing them into the cement? Or do you mean attach wall ties to the plywood/studs behind the plywood and have that go into the cement? What kind of wall ties should I use?

I'm not worried about using an insert in there as this is all somewhat temporary. Long term, the entire chimney is going to come down, as is this entire wall and we are opening it up. But that might be in about 10 years or so.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,106
central pa
Dumb question... ...where would I be putting the wall ties and how. Am I attaching wall ties to the bricks and encasing them into the cement? Or do you mean attach wall ties to the plywood/studs behind the plywood and have that go into the cement? What kind of wall ties should I use?

I'm not worried about using an insert in there as this is all somewhat temporary. Long term, the entire chimney is going to come down, as is this entire wall and we are opening it up. But that might be in about 10 years or so.
Yes you will attach wall ties to the brick and to the plywood. Then you bend them so they fit into a mortar joint in the stone
 
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midfiman

New Member
Sep 23, 2019
10
N/A
Thank you. I will definitely use wall ties then.

My other question that i'm hoping someone can answer is what do you guys think of the steel angle going across the top? This would help support the stones that are directly above it. Yes, I'm going to wire lath on the top, scratch coat and then cement the stones on there, but it's 2-2.5" of cement then 2-3" thick stones going on there, so I don't know how much weight the wall is holding vs the downward weight. the idea was to have a steel angle, maybe 3" high, 4" depth running across the top of the firebox, supported by the columns of cement on either side.

Not sure if that makes sense or not.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,106
central pa
Thank you. I will definitely use wall ties then.

My other question that i'm hoping someone can answer is what do you guys think of the steel angle going across the top? This would help support the stones that are directly above it. Yes, I'm going to wire lath on the top, scratch coat and then cement the stones on there, but it's 2-2.5" of cement then 2-3" thick stones going on there, so I don't know how much weight the wall is holding vs the downward weight. the idea was to have a steel angle, maybe 3" high, 4" depth running across the top of the firebox, supported by the columns of cement on either side.

Not sure if that makes sense or not.
It is called a lintel and yes you need it
 

webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
You mentioned above about using plywood behind the stone. This is not necessary and shouldn’t be used on a fireplace. I guess I overlooked the fact it’s veneer stone. The mortar will bond really well to the existing brick, I don’t see any need for brick ties or mesh. I used mesh on mine, only because the brick had been painted.
 

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midfiman

New Member
Sep 23, 2019
10
N/A
Hi webby. Thank you for your reply. Let me clarify. The plywood is only on the top half of the fireplace (which you can see in the first pic) to build it out to the same level as the bricks on the bottom half. This 2x4/plywood rectangle is being built on top of the existing 2x4 wall behind it which the chimney is up against. So its two levels removed from the chimney and a good 2ft above the firebox opening, so I don't think it would get hot at all.

That being said, yes, its a veneer or sorts, in that its about 2-3" thick real stone (heavy), and then another 3" or so of cement, so in total it comes out about 5-6" from the existing brick/wall. The mason recommended thick cement to keep from cracking and help with the sheer weight of the stone. So my concern is how much "wall holding power" there is when there is about 2-3" of cement present before the back of the stone, and how this would affect how well it sticks to the existing brick.

Likewise, I wonder how this would affect it holding up on the scratch coated mesh lath that would be applied on the top half as well. I know that from everything I read online, scratch coated mesh is very strong for veneer stone, but that seems more applicable to stones that are cut 1" thick or so, with just a thin layer of cement behind it attached to the mesh. In my case, its a lot more weight being attached here.

Lastly, if that's not enough, I wonder about lintel vs arched opening. Am I right in that if I have the mason build an arch with a keystone, that can support all of the stones above it (though if they are indeed attached to the wall correctly, a lot of the weight would be supported there)?

Sorry for so many questions, but my knowledge in this area is fairly limited compared to you all!

Regards
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,106
central pa
Hi webby. Thank you for your reply. Let me clarify. The plywood is only on the top half of the fireplace (which you can see in the first pic) to build it out to the same level as the bricks on the bottom half. This 2x4/plywood rectangle is being built on top of the existing 2x4 wall behind it which the chimney is up against. So its two levels removed from the chimney and a good 2ft above the firebox opening, so I don't think it would get hot at all.

That being said, yes, its a veneer or sorts, in that its about 2-3" thick real stone (heavy), and then another 3" or so of cement, so in total it comes out about 5-6" from the existing brick/wall. The mason recommended thick cement to keep from cracking and help with the sheer weight of the stone. So my concern is how much "wall holding power" there is when there is about 2-3" of cement present before the back of the stone, and how this would affect how well it sticks to the existing brick.

Likewise, I wonder how this would affect it holding up on the scratch coated mesh lath that would be applied on the top half as well. I know that from everything I read online, scratch coated mesh is very strong for veneer stone, but that seems more applicable to stones that are cut 1" thick or so, with just a thin layer of cement behind it attached to the mesh. In my case, its a lot more weight being attached here.

Lastly, if that's not enough, I wonder about lintel vs arched opening. Am I right in that if I have the mason build an arch with a keystone, that can support all of the stones above it (though if they are indeed attached to the wall correctly, a lot of the weight would be supported there)?

Sorry for so many questions, but my knowledge in this area is fairly limited compared to you all!

Regards
Don't worry so much about attaching to the wall. The weight will be supported by the floor the face is stiting on. The attachment to the wall is only there to keep the face from moving laterally. I also wouldn't fill the space between the new one old face it will lead to more cracking instead of preventing it.
 

midfiman

New Member
Sep 23, 2019
10
N/A
Thank you bholler. Sorry, what do you mean about not filling the space between the new one and old face? This is basically going to be a cement wall of sorts attached to the brick (bottom half) and lath covered plywood (top half) and then faced with the stone. Since the stone is wider and heavy, we are essentially almost drystacking it and then backfilling.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,106
central pa
Thank you bholler. Sorry, what do you mean about not filling the space between the new one and old face? This is basically going to be a cement wall of sorts attached to the brick (bottom half) and lath covered plywood (top half) and then faced with the stone. Since the stone is wider and heavy, we are essentially almost drystacking it and then backfilling.
I am saying don't backfill it just lay the stone and attach it with wall ties. No need for mesh either. This is not veneer stone it is facing stone. Make sure the floor you are building on can support the weight of this wall