Pinning a Wood Mantle Beam to Masonry
Here are several suggestions for attaching a heavy wood mantlepiece to a masonry chimney. December 27, 2008
I am interested in tips on installing a large fireplace mantle cedar beam. I would prefer not to drill holes through the front of the beam to avoid the appearance of filled holes.
(Cabinet and Millwork Installation Forum)
From contributor J:
Depending on how large "large" is you can lag a 2 x 4 into the masonry, cut a mortise in the back of the beam and use landscape screws ( hex head thin lag type screws ) up thru the bottom or from top whichever is less conspicious. Steel angle iron also but that is more complicated to attach to.
From contributor T:
We used to drill 3/4 bores into masonry, install steel threaded rod into bores with epoxy leaving rod stick out proportionate to beam size and slide the drilled beam over the rods with epoxy in these holes. The bigger the beam the more holes you need; like stacked rods (one up one down) on a 12 inch wide beam. After epoxy dries you can't move them though! Just make sure the beam is tightly bedded to the masonry and scribe if you have to.
From contributor D:
Ive done it contributor Js way many times. I only screwed from the top though. Counter bore the holes and plug them with plugs from the drop.
From contributor V:
I did one a couple weeks ago. Instead of threaded rod and epoxy, I used 3/4" galvanized pipe and PL Premium. After it set, you can stand on it.