El Sobrante Chimney, 2018

This is the chimney inside the same El Sobrante home where we rebuilt the yard and patio. And like the yard, it was done on a budget, with the homeowner assisting with much of the work.

Building a perfect box around a boulder

The existing chimney was large and dated, and didn’t fit the ranch-style home. Demolishing it would have been expensive and disruptive, so we chose to build over it. Stone overhangs were cut back with an angle grinder and a 4.5-inch carbide blade, and a new heat-resistant, non-combustible frame was built around the old masonry, including a box above the mantle.

There wasn’t a plumb, level, or square surface anywhere on the original fireplace. So the backer was hung on shims, furred out to create true planes while still reaching back to solid support. It’s like building a perfect box around a boulder: every shim and support depth is different, and once the backer is up, you can’t see behind it to measure. It takes patience, and a lot of checking with a level at every step.

Real slate, mitered corners

The homeowners chose real slate in a medium format, one foot by two feet. Slate is beautiful, but it’s natural stone, so it has to be sealed and it’s harder to work with than porcelain. We decided to miter every corner rather than cover the edges with trim. Mitering on a corner that isn’t 90 degrees is where it gets tricky. The angle has to be measured with an angle finder and split exactly in half, so the two tiles meet cleanly.

The cuts were made on an overhead sliding wet saw. It had plenty of power, but I’ve since moved to a table-style wet saw, with the blade coming up through the table and the tile sliding across it. For medium and large-format tile, that setup is simply easier to control.

A raised hearth and a television

A large raised hearth was built over the old stone base, giving the fireplace a wide, solid ledge.

The twist was that the owners wanted a television mounted above the fireplace. Making that structurally sound over a new frame, around an old chimney, was not easy. A TV mount needs solid anchorage, not just tile and backer, so the support had to reach through the new surface to something that wouldn’t move.

What I’d do differently

A load-bearing beam runs into the chimney, and the ceiling sags where it meets the fireplace. That’s the house, not the new work, and there’s really no way to hide it. Looking back, I’d add a piece of wood or tile trim along the top to draw a straight line and conceal the bend. Still, the result was a clear improvement over where they started: an original design, custom-built, that finally fits the house.

Thinking about a fireplace update? See what we install, or send photos for an estimate.