There are a lot of terrific and helpful ideas on Instructables for installing a floating wood shelf. Here’s what I did that’s a bit different when using a substantial chunk of wood. My mantel also has mitered wrap-around corners which you don't often see, but that's the look I wanted.
Bitter cherry, also called Oregon cherry (Prunus emarginata) is a native tree that popped up in our woods when it was replanted in 1988. I wondered what the grain and color would look like when it was milled. It has an interesting bark, that much I knew.
Step 1: Mill and Dry the Log
I picked a tree I liked and thinned the woods by one cherry tree. (Like George Washington, I can't tell a lie, I chopped down that cherry tree.) I parked the log in the barn to dry for about five months, then had it milled to about a five foot 5-1/2″x7″ with bark edge on the 7″ width.
As control against splitting and twisting, I scored a few slices on the back side (the side that would go against the wall) in varying depths, the deepest being the middle cut over the tree center at about 1-1/2″ deep. Then I primed the sawn sides and left the log to dry, standing up, for about 3 more months.
Step 2: Carefully Cut the Corners
I was hoping to preserve the bark, so cutting and fitting the corners was tricky. I sanded down the precautionary slices (which were on the bottom) and cut the pieces based on a 45 degree angle. I sanded, splined and glued it all together, then applied a clear finish.
The bark might eventually peel in the dry interior of our house, but underneath looks pretty cool as you can see in the photo, so I really don’t care.
Step 3: Mount the Log to the Wall Pt. I
I used a hand-made hanger and bracket system to install the 35+ pound mantel. First I hollowed out two slot holes at 9/16″ depth on the back of the log. Metal straps, recessed so that the mantel would fit flush with the wall, were screwed across the hole slots as shown.
To note, these photos show the cuts made earlier to prevent the log from splitting or twisting.
Step 4: Mount the Log to the Wall Pt. II
Then I fabricated metal hangers that would fit inside the slot holes and screwed them to the wall studs. Each 1/8" thick metal hanger has spacers between it and the wall that are thick enough to allow the brackets to slide easily over the hangers while providing a tight fit. I made sure that the hangers matched up perfectly with the location of the brackets on the back of the log.
Step 5: Hammer It In, Carefully
Positioning based on blue tape on the log and on the wall, a little bit of gentle hammering with someone else holding on, and the mantel is easily installed. This secure fastening system provides a good fit against the wall with no chance of failure.
Step 6: Admire Your Mantel!
It's like having a bit of woodland inside the house. More than a year later, the bark is so far staying put in spite of our warm, dry interior.