Can you add cement board to shorten a firebox?

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chadrob

New Member
Oct 14, 2020
2
Tacoma
Hi,

My wife and I demoed a river rock fireplace facing and are now wondering... how can we clean this mess up? Our main question is: can we simply place a cement board over the front of the firebox to shorten it, or do we need to lower it with fire resistant bricks?

We are thinking:

1. Mortar to smooth out the the brick and cement blocks.
2. Trim the fireplace with cement board (including a piece that will go over the top of the firebox to lower it by X inches).
3. Add a tile surround.


Bonus questions:

1. Do you see any structural concerns that we might want to get checked out by a pro?
2. Is there anything we should consider doing to ensure there is no cold draft?
 

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We have a contractor that is supposed to come and handle it in April (we wanted to get the floors in first so the hearth will sit flush), I'll update the thread when it's done.

There was also a need to add another support to lower the firebox, so it's worth having someone come take a look just to be sure... also there is quite a bit of math to create an optimal firebox to avoid backdrafts. I believe the contractors plan is, is to mortar the sides after adding the support for the top row of bricks. Below are the details from the quote:

*Install additional angle
iron for support & lower
firebox height.
*Attach Metal lath to
existing masonry and
apply stucco base coat
for Brick install
*Install Full Faux Marble Heart
& Faux Marble surround as
per clients specs.
*Grout & clean all brick

Quote was $2,600.
 
We have a contractor that is supposed to come and handle it in April (we wanted to get the floors in first so the hearth will sit flush), I'll update the thread when it's done.

There was also a need to add another support to lower the firebox, so it's worth having someone come take a look just to be sure... also there is quite a bit of math to create an optimal firebox to avoid backdrafts. I believe the contractors plan is, is to mortar the sides after adding the support for the top row of bricks. Below are the details from the quote:

*Install additional angle
iron for support & lower
firebox height.
*Attach Metal lath to
existing masonry and
apply stucco base coat
for Brick install
*Install Full Faux Marble Heart
& Faux Marble surround as
per clients specs.
*Grout & clean all brick

Quote was $2,600.
Is this for use as an open fireplace? If so metal lathe and regular mortar is not going to hold up well. Also make sure you have all of the required thicknesses of masonry around that box for use as a fireplace. It looks thin