When we built our house over 20 years ago, the fireplace we wanted was river rock and with a firebox with a firebrick liner. What we could afford was a zero-clearance fireplace with a stone surround. For those who have not had experience with one of these fireplaces, they are essentially a sheet metal box with enough insulation to allow the unit to be installed directly next to framing, sheetrock, and etc. To keep the fire from taking out the inner metal panels, the firebox is lined with refractory panels - these panels are essentially cast firebrick.
Over the years, the rear refractory panel started to crack on our fireplace. It was bad enough this year that I didn't think it was safe to use, so I got online with the make and model of the fireplace and found a company who could order a new panel. Ran about $110 with free shipping and took about 6 weeks to arrive at my door.
In order to install the rear panel, the bottom panel and one of the side panels needed to be removed. I pulled out all of the fasteners and got the shop vac to get rid of the last of the ash. Unfortunately, the bottom refractory panel was toast (so to speak) - much of it I vacuumed up and what was left wasn't worth trying to save. Oops.
Time to order a new bottom panel, right? Except no one has one or seems to be able to order one. I could have ordered universal side wall panels and used one of them on the base, except they have no reinforcement at all, so I decided to do cast a new panel in place. I order some stainless wire screen (about 1/4" grid) to use as reinforcement and 25 lbs of castable refractory cement. Fortunately, the front berm (?) of the original base was still OK, so I cut off what was left of the rest of the panel. I trimmed the stainless screen and bent the edges down to raise the screen about 1/4" from the metal bottom, so it would be embedded in the refractory cement.
After that, I pulled everything out and laid down parchment paper to keep the cement from sticking to the metal so that I can take it out if this doesn't work. This is where I ended up. The lip at the front is there to help bond the berm in the front to the rest of the panel.
After mixing up the castable refractory cement according to the directions, I mudded the lip under the berm and dropped it into place, then started casting the panel. Getting the refractory cement through the stainless mesh was a pain. Used a narrow putty knife to do that and then added more cement to the rest of the panel bring the thickness to between 1/2" and 3/4". Used a 10" drywall knife to smooth it out, but not completely, since the refractory cement instructions said to leave the surface rough so it would dry properly.
This is where I ended up this afternoon. Supposed to keep the material moist for the next 24 hours. Also, I was originally going to let the entire panel harden and then pull it out to remove the parchment paper. I have changed my mind on that since the worst thing that could happen is that the parchment paper could catch on fire. Hopefully, fire in a fireplace will not be a huge problem.
Will post again when I can start a small fire to complete the curing of the refractory cement.
