DIY Faux Beam Floating Mantle

Hello! I had some questions about how we made our mantle after my last post on our home reno update, so I thought the easiest way to explain would be showing you exactly how we did it. So here is how we made our faux beam floating mantle.

Supplies needed:

  • Wood: see notes for dimensions and quantities
  • Clamps
  • Wood glue
  • Table saw
  • Miter saw
  • Drill
  • Screws
  • Sandpaper
  • Stain and Poly
  • Rags or brushes to apply stain/poly


  • Start by measuring the length you’d like your mantle and the depth. Our fireplace is 6 ft wide, so we decided our mantle length was 5 ft, width was 7.5 inches. You’ll need enough wood for the length/width x 3, for each of the exposed sides of the beam, PLUS a bit for each end cap.
  • We used three 8ft 2 x 8s – we used plain old construction lumbar. You’ll end up with some scrap but you’ll need some of it for your caps.
  • You will also need wood for the inside of your beam to help space it when you build it and also so you can mount it onto the wall without any noticeable support. We used two 8 ft 2x 6s and cut them down to size later.
  • You’ll be cutting the 2 x 8s at 45 degree angles so the joining seams are in the corners and looks seamless when finished – like a real beam!


  1. To start, rip boards down using table saw if needed.
  2. For 2 long boards: cut 45 degree miter cuts on three of the four 2 inch sides of your mantle’s top (one long, 2 short sides cut), leave one of the long sides squared as this side will go against the fireplace.
  3. For the last long board: cut 45 degree miter cuts on ALL of the four 2 inch sides
  4. For your end caps, cut three of the four 2 inch sides at 45 degree angles – this way, all seams land on edges and are barely noticeable.
  5. The cleat and inner support board will be the same size and are left rectangular – cut these to the length and width of the front mantle board’s inner dimensions – the smaller side that the 45 degree angles point to.
  6. Assemble all pieces following pictures below (the end caps are left off so you can see the inner workings ) – glue and clamp all joining edges but DO NOT glue the cleat in place- just use it for support for now. NOTE: the picture skews the bottom of each side piece, they are actually flat with the bottom cleat, not angled down.
  7. The end caps can now be glued and clamped.
  8. Once the faux beam is together – sand, stain and poly it before you hang it. We sanded the hard angles so they were a bit rounded like a worn beam.
  9. Screw the cleat in place on fireplace

12. Place the hollow beam over the cleat and secure in place with screws angled through the top of the beam into the cleat towards the wall so you cannot see them from the front.

And that’s it! I hope this explains it well. Please let me know if you have any questions by commenting below or sending me an email at

Next up is installing the hearth and stone! Keep your eye out for our full fireplace makeover soon.