I always wanted to build my own floating shelves and had seen some
similar ideas but they were not quite as solid so took a little time to think
about how I could improve on the ideas I had seen and still keep it simple.
This is what i came up with.

Step 1: Materials

1) Piece of solid wood for the shelf
2) 6mm thread bar
3) 6mm nuts x2
4) 6mm expansion bolts x2
5) oil to finish wood off (optional)

Step 2: Tools

1)spirit level
2) steel ruler
3) Pencil
4) selection of drill bits
5)Drill with hammer function
6) hacksaw
7) orbital sander
8) Pliers
9) Spanner

Step 3: Prep, Mark, Measure

I started by giving the shelf a sand with the orbital sander just to clean up any very rough
spots and remove any splinters. (wanted to keep the shelf fairly rustic looking.)

Note: If you gonna radius the edges be sure to keep the back edges square
otherwise i will look funny where it meets the wall.

Next mark a line along the center of the length of the shelf then
take a rough measurement to get an idea of the pitch of the holes for fixings.
Try to leave at least 30mm from the edge of the shelf and also look out for things like knots,
nails, (if you are using a reclaimed piece of timber) or any other thing s that might get in the
way of your holes. (mine came to 490mm)

Note: I didn't mark exactly 30mm from each end and the measure the distance between those points.
I just held my ruler along the back of shelf eyeballed the distance i wanted from either end and rounded
to the closest even measurement.

Step 4: Mark Out Holes for the Shelf on the Wall

Hold the shelf up to the wall to get idea of exactly where you want it and make a reference mark.
Now from your reference mark a horizontal line an then measure and mark the pitch of your holes
according to the measurement calculated in previous step.

Step 5: Drill Holes in Wall

Now starting with the smallest masonry bit you have (my case 3mm) drill holes into
the wall on marks you marked out for shelf. Start your first hole without hammer to
prevent drill from running off of marks and once started switch over to hammer.
Go up in steps until you get to final size for expansion bolt. Try to keep drill as straight
and level as possible while drilling holes.

Step 6: Measure, Mark, Drill.

Now measure the exact pitch of your holes in the wall and mark the pitch on the back of your shelf.
Now drill 6mm holes on your marks on back of shelf.
Note: Make sure to check length of bit to depth of shelf and mark bit with a piece of tape to make
sure you don't drill right through the shelf.
Now counter bore your holes with a 12mm bit about 10mm deep.

Step 7: Assemble the Fixings

Disassemble the expansion bolt keeping the bolt for future project. Turn
a nut onto thread bar then slip on the washer and then turn into expansion
bolt.

Step 8: Secure, Measure, and Cut Fixings

Insert the thread bar into the hole in your shelf until t is all the way in then
mark and measure the depth of the hole.
Now insert the expansion bolt into the wall hold the thread bar with a pair of
pliers and tighten the nut with a spanner.
Now taking the measurement from earlier mark +-5mm shorter and cut off
remaining length of thread bar.