Best way to build mantle

[Braden Nichols]

My aunt has asked me to build a fireplace mantle for her new ranch house. She sent the below picture to use as a model. It will be clear alder. I am trying to figure out the best way to build this. All solid wood in sections? Hollow? Any advice is appreciated.
210103

[Peter Quinn]

Hollow box with mitered corners, reenforce corners from inside with blocks screwed and glued on, plywood bottom set in a dado like a raised panel, glue up corbels, flush trimming as you add thickness, solid top that overhangs on three sides, small crown or bed molding to transition from the mantle's "foundation" (thats mantle speak for the hollow box part) to the top. You could buy the corbels if you don't want to or are not equipped to make them. Draw it up to get all proportions right. Leave a scribe on top and sides that touch stone for a seamless built in look

[Robert Chapman]

I agree with what Peter says except for the solid top. I would use plywood - maybe a double thickness so as to avoid wood movement. In that environment with major heat/moisture changes you need to use material with minimum movement.

[Paul Incognito]

Peter's got the right idea. As far as solid vs plywood for the top, I've used solid white oak, poplar, birch and cherry for mantle shelves and never had a problem. Of course YMMV.
Paul