Learn how easy it is to build a simple fireplace surround and mantel from MDF to beef up an existing brick fireplace.
In the first part of my fireplace makeover tutorial, I shared how to tile over a brick fireplace. Today, I’m going to share how we built out our existing surround and DIYed a new mantel. If you haven’t already you can also see my plans for the fireplace makeover.
How To Build a Fireplace Surround with MDF
and Install an Electric Fireplace
When we took the old mantle shelf off we were left with a surface almost completely flush with the wall (one of the main reasons for this makeover). Before we could tile the hearth, we covered the brick with 1/4 inch MDF. We stuck it directly to the brick using some Liquid Nails and use our nail gun on the corners where the MDF met. We didn’t both mitering the edges and just butted them since we knew it would be covered with trim later on.
We used the same sheet of MDF to cover the sides of the surround and across the top. We measured them to fit what already existed since the built-ins on either side preventing us from going any wider. We secured the MDF to the existing wood surround using our nail gun.
Next, I began to add some of the lattice pieces to the front of the hearth. We started by boxing it out (top piece, bottom piece then left piece and right piece). Finally, we cut the two small vertical pieces that would form the inner boxes. The lattice pieces are attached mostly with liquid nails but with a few nails in the corners just to make sure they would stay in place. The lattice repeats on the side of the fireplace, too.
At this point we decided to build our mantel before deciding how far out we wanted to build the surround. It was one of those things that we just needed to see in real life and not just on paper.
The mantel itself is a very simple box. We purchased pre-primed 1 x 4’s and started by attaching the back board to the existing wall with our nail gun. The bottom piece was nail in place and then the side pieces. Finally, the front piece. No 45 degree angles needed again, since we knew the exposed sides would be covered by crown when we were done.
Note: In hindsight, it would have made more sense to build the box first and THEN install it. If you have a kreg-jig, pocket holes would work great to secure the sides. But our way worked fine in the end.
When we were happy with the box, we attached a 1 x 8 pre-primed board to sit on top and form the actual mantel.
Once the mantel was built, it was easy to figure out how far out we needed the build the rest of the surround. Again, we kind of just boxed it out, this time using 1/2 inch MDF. We attached the side pieces first, then nailed the front piece in. Then we added 1 x 4 pieces to the bottom of the vertical sides to create some depth. These pieces were cut at a 45 degree angle to create a clean, mitered edge.
By the way, we found the MDF very messy to work with (we are STILL cleaning up saw dust a month later). I’m not sure our circular saw was up to the job – a table saw would have made cleaner cuts – and the pieces were large so cutting them with our miter saw was a no-go. SO, we just butted the edges and figured some spackle and sanding would help hide the fuzzy raw edges of the MDF (note: they did! The sides came out perfectly smooth and painted like a dream!)
Next up we worked on finishing the shadow boxes using our pieces of lattice trim. We always do the perimeter boxes first and then full in with the little pieces. Doing it that way makes the cuts a lot quicker. At this point the whole design really started to come together.
In order for the electric fireplace to sit into the existing fireplace surround, we needed to build a box for it to sit in. The particular electric insert that we purchased screwed in on the sides only, so we decided to only do 3 sides to our box – left, right and bottom. The bottom piece needed to be raised up from the ground enough so that to top of the insert would align with the top of the opening and cover an imperfections in the tile right around the edge. We did the math and figured all that out, then screwed the wood into the brick with some masonry screws and as well as liquid nails.
I forgot to take a photo before we attached the backer board to the wood but you get the idea, right?
At this point, the electrician had finally come and installed the outlet inside the fireplace so I was able to go ahead and finish tiling. P.S. Did you notice the little red hammer? My kids love to help and have kiddy versions of ALL our tools!
We attached some crown moulding the front using various YouTube tutorials to help us cut the mitered edges. The first piece of crown we bought was 4 1/2 inches and too large. Even though it fit on the front under the mantle top, we couldn’t get the edges to meet, so we had to go down to a 3 1/2 inch piece.
Next came the dirty part – lots of grouting, cleaning, spackling, caulking and sanding. I sealed all the fuzzy edges of the MDF with a light coat of spackle, let it dry and sanded it with fine grit sandpaper. All the nail holes will filled with spackle and sanded once dry. Finally, all the seams were filled with caulk. I made sure that the wood had no imperfections and was very smooth before priming it with 2 coats of my favorite primer and sealer. This stuff completely seals the wood so that you don’t ever need to worry about bleed-through.
I lightly sanded between each coat of primer to ensure that I was keeping the surface as smooth as possible. I allowed the primer to dry for 24 hours and then applied 2 coats of Sherwin Williams Extra White in a satin finish.
Then FINALLY, after what seemed like an eternity and a whole lot of late nights, we installed the electric fireplace insert.
I was SO excited for it to be done that I had all my Christmas decorations back up before I took photos. Isn’t it beautiful though?
In the end, we pretty much built this entire fireplace mantel and surround from scratch. But I have to say it was worth it. Our living room has been completely transformed! Our new fireplace is proportional, substantial and fits our space. It wasn’t the most difficult DIY project but it certainly was a little frustrating at times (I’m looking at you crown molding!) and more than a few swear words were uttered. We’re so happy with how it turned out and we very pleased that we DIYed the entire thing ourselves and saved a lot of $$ as a result!