“It’s time for a fireplace update.” Fast forward 4 weeks and the aroma of freshly cut walnut and poly still linger in our living room as I write this. Nothing fancy here, just a simple paint and build, striving for simplicity and clean lines. I’ve detailed everything out below, minus the exact dimensions since it’s custom to our space and different for each house. If you have any questions, feel free to email me or leave a comment below!

As with each DIY project I’ve posted here, I’m not a professional craftsman and I don’t play one online. Detailed pictures and further info located in each section as you expand them. Best of luck!

Total Cost

  • Walnut Boards$200
  • Common Boards + Screws$50
  • Primer + Paint$50

How To

Expand each step for more instructions and photos

1. Out with the Old & Deep Clean the Brick

  • The demo of our old mantel was pretty straight forward
  • I began by removing the bottom portion
  • Popped the 2 sides off
  • Gently removed the existing top mantel – The key here is to not do any more damage than needed to remove everything
  • Our fireplace is a wood burner, so I needed to do a good, deep cleaning of the brick to make sure all loose pieces and soot were removed – This part is important so the primer has a chance to adhere well to the brick
  • Remove excess paint and caulk leftover from the old mantel

2. Touch Up with Spackling & Fill Gaps

  • Seal holes & unleveled areas of the wall with spackling
  • Paint in the borders on the wall around the old mantel and the spackled areas
  • We decided to not use corner round going up the sides, between the wall and brick, and instead filled all the mortar gaps between the wall with caulk so it blended evenly

3. Paint the Brick - Oil Based Primer + 2-3 Coats of Indoor Latex Paint

  • Tape off the floors and fireplace hearth for clean lines
  • Use an oil based primer as your first coat and be generous to cover all spots
  • After the primer drys, paint 2-3 additional coats with Indoor Latex Paint – We did 3 coats to make sure everything was covered and sealed for extra protection for our Fall / Winter burning

4. Build & Paint Lower Mantel

  • Our bricks didn’t go up high enough, so we decided to add a lower mantel piece to fill in the area and allow the top mantel to rest at the same spot as the previous one
  • I used 6″ x 1″ common board and sawed miter cuts on the ends so it pieced together seamlessly at the edges
  • Apply 2 coats of the same Indoor Latex Paint from the brick and let dry

5. Hang Lower Mantel - Common Board Braces

  • Screw common board perpendicular to the inside of the lower mantel to form bottom braces – I used the Kreg Jig to screw holes into the common board, 2″ from the bottom
  • Place the lower mantel with the new bottom braces on top of the brick and trace lines on the wall, aligning with the top of the common board so we know where to screw wall braces in
  • Find studs in the wall and screw 2″ x 4″ blocks into them, aligning the bottom of the blocks with the lines from the lower mantel braces you just traced – I used the Kreg Jig to screw holes into the blocks so I could add a little reinforcement to the braces
  • Place the lower mantel on the fireplace so the braces on the back wedge between the brick and 2″ x 4″ blocks, securing it to the wall – the weight of the top mantel will help place the lower mantel so it won’t move

6. Build Walnut Mantel with Cleats for Wall Support

  • We used 2″ thick uncut walnut lumber and I sawed it into a box that was 8″ tall 9″ deep and 72″ long
  • After cutting the pieces to size (base the length and height to your own fireplace), I planed the tops and sides for even, smooth fits
  • I sawed miter cuts on 3 edges for the top, front and both side pieces so everything boxed out nicely and it looked like one solid piece – the edges touching the wall should be flat, so no miter cuts for those
  • The bottom piece I left with straight cuts and drilled holes all the way around with the Kreg Jig to build a strong base for the boxed out look
  • Assemble the bottom, front and sides pieces together with glue, clamps, painters tape and screws
  • To help bond the miter cuts together, I clamped the sides to make sure they were seamless, taped with painters tape to keep the hold, removed the clamps and applied glue – I put all the pieces back together and reapplied the clamps for extra pressure
  • While the pieces are bonding, cut a 2″ x 4″ piece in half, at a 45 degree angle, to form a french cleat on the top mantel piece and wall – See here for more info on french cleat joints
  • Screw the appropriate cleat piece into the top mantle section, making sure everything lines up so the french cleat wedges into the wall securely instead of the opposite where it would slide away from the wall
  • Cut 2″ x 4″ blocks the exact height of the inside box to help support the top weight
  • Adjust appropriately so all the miter cuts line up seamlessly on the front & sides with the top piece and use painters tape to keep everything aligned
  • Add a generous amount of glue and clamp to apply more pressure, creating a tight bond

7. Sand & Poly Walnut Mantel

  • Use appropriate sandpaper grit to remove rough spots, ending with a 180 or 220 grit for a nice smooth finish
  • Apply 2-3 coats of polyurethane – we used a matte, non-gloss finish
  • Let cure for 24 hours

8. Hang Walnut Mantel

  • With one half of the cleat screwed into the top mantel, locate the studs on the way and screw the other half into it
  • Measure the height from the bottom of the mantel to the bottom of the cleat, marking the wall with the measurements – I was slightly off on my first attempt, so I had to tweak the holes and position of the cleats slightly so the top mantel rested perfectly on the bottom one and it was a snug fit between the mantel and wall

9. Caulk & Paint Touch Ups

  • Caulk around the lower mantel / brick and apply the appropriate wall & brick paint to fill anything in

Author Ian Schneider

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