Single board mantel

[Eduard Nemirovsky]

I have 6 feet, 8" wide and 3 and 7/8 thick walnut board. I planning to do mantel over our fireplace. Wall surrounding fireplace - drywall, but we are going to do stone veneer.
Board is very heavy, probably -35-40 lbs. My concern - weight of this beast and securing it to the studs.
Questions:
1. Should I make board 2 3/4 - 3" thick - less weight? What is the usual thickness of single board mantel, if any standard exist.
2. I am planning to use rebars in studs and holes in the mantel, is this reasonable weight support design?
3. What kind of glue should I use to fill in holes in mantel for rebars?
4. Should stone veneer will going around mantel or mantel going over stone wall?
5. What to use for finishing?
Thank you for any info.
Ed.

[Eduard Nemirovsky]

Actually I just calculate approximate weight with 8% MC - 59 lb. Ouch. No wonder I have a problem to handle it for planning.

[Jamie Buxton]

If you like the look of the thick board, use it that way. There is no standard for the weight of a mantel, and the wall can support a mere 60 pounds. (A kitchen upper loaded with plates and such can easily weigh that much.)

Have you thought about how you're going to get the rebar to line up with the holes in the mantel? They not only have to be spaced correctly, but the angles have to be right too. You can help yourself by making the mantel holes big. But then you need an adhesive that will bridge gaps, while not drooling out of the holes. You could use construction adhesive. Or you could use epoxy. Simpson sells epoxy intended for gluing rebar or hold-down bolts into foundations. The useful thing about it is that the nozzle does the mixing for you. http://www.strongtie.com/products/an...ET/index.html#

Stone first or mantle first might depend on the design. If the stone only goes up to the underside of the mantel, I'd install it first, then the mantle. You get to run the stone to wherever it goes, then set the mantle right there. If you install the mantle first, then you have to get the stone to stop right at the wood; stone isn't that easy.

[G Douglas Fowler]

Ed, you didn't say how far out the stone will be from the wall. If the stone is built out from the wall it can help support the mantel. Visually, if the stone veneer is thin and placed directly on the wall, the depth of the mantel could look out of proportion. That being said, I installed a floating mantel with the method you contemplate. I used smooth 1/2" steel rod, 3" into the stud and 3" into the mantel and did not glue: rebar is irregular and getting a good tight fit can be difficult. The weight of the mantel and the tightness of the fit of the support rods was sufficient to keep the mantel firmly in place. If you are concerned about movement, use epoxy. You might want to consider use a drilling jig to make sure the holes are dead level and perpendicular.
Doug

[Eduard Nemirovsky]

Thank you, guys.
Yes for how to drill a holes. I am planning to secure piece of plywood on studs, same size as a mantel board, then drill holes thru plywood and studs. Transfer plywood on back of mantel and use it as a template for holes in the board.
Jamie, thank you for the link.
Any advice for finish? Do I need something heatproof? or heat tolerant?
Ed

[Jamie Buxton]

There is building code for a mantel that projects as much as yours does. It has to be at least 12" above the fireplace opening.

I'd just use ordinary varnish on the walnut.

[Yonak Hawkins]

I'm not an engineer but I would be suspicious of that much weight protruding that far, being supported solely by rebars, especially if they're not positively secured in the studs and in the mantel. It seems to me that, over time, the front edge would tend to sag.

[Jerry Miner]

One way I've done this is to use long lag bolts, screwed into the studs, with the heads cut off--positive attachment to framing, and pretty easy to keep lined up. I over-drill the holes in the shelf to provide some tolerance.

If the stone stops at bottom of mantle, I would install mantle first, then stone and grout to mantle.

If the stone continues up above, I would set the stone first, and not bury the mantle in the stone.