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How to Turn a Reclaimed Beam into a Fireplace Mantel

Ask This Old House carpenter, Nathan Gilbert helps a homeowner turn a reclaimed mantel into a fireplace mantel.

In this video, Nathan Gilbert helps a homeowner turn a reclaimed mantel into a fireplace mantel.

Steps for Using a Reclaimed Beam as a Fireplace Mantel:

  1. Measure approximately 55-56” off the floor, this is the average mantel height. Make sure the height is at least 12” above the top of the firebox, which is code.
  2. Use joints of bricks to mark the center of the fireplace. Do not drill through the brick, it is more difficult and you risk damaging the brick. It will also be stronger to go through the mortar.
  3. Find the center of the fireplace using the mortar lines.
  4. From the center mark, measure out to the mortar line that is closest to 16” on each side.
  5. Next, make sure all marks are level.
  6. Drill pilot holes at each mark to make it easier to drill the larger bit.
  7. Drill with the larger masonry bit and then clean out the dust and debris with a brush and/or vacuum.
  8. Apply epoxy into the hole and insert the threaded rods.
  9. Use 2x4’s to secure the rods and make sure they are level while the epoxy cures.
  10. Cut the mantle down to the desired length. Use a circular saw or, like Nathan, a two-person crosscut saw to keep authenticity.
  11. Use a block plane to clean up 5 of the 6 edges. The sixth edge is not needed as it will be against the wall. Cleaning up the beam will allow a smooth enough surface to apply a finish, without eliminating the marks from the axe.
  12. Transfer the measurements from the wall onto the beam and drill.
  13. Apply a finish to the five visible sides of the beam. A common finish for old wood was tung oil. It will not darken the beam too much and will help celebrate all the imperfections of the beam. Apply one coat to start and let set for about 15 minutes. Dry off with a lint-free rag. Focus on wiping the high glossy spots and the knots, as they don’t soak in the oil as well. If desired, apply a second coat in 24 hours.
  14. Insert epoxy 3/4 of the way into the drilled holes of the beam.
  15. Lift the mantle into place and push firmly onto the rods.

Resources:

The homeowner found the reclaimed beam at the Brimfield Antique Flea Market, but materials like the beam can be found at most flea markets and also at reclaimed lumber yards. The two-person crosscut saw belonged to Nathan’s grandfather, but similar saws can also be found at flea markets and antique tool shops.

To secure the beam to the fireplace, Nathan used ⅝” threaded rods, which can be found at any home center, and Thixo 2:1 Epoxy System, which is manufactured by TotalBoat.

The other tools and materials Nathan used to secure the mantel to the fireplace, including the drill, block plane, and sandpaper, can all be found at home centers.


Materials:


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