A neighbor asked me to help him with a project with bricks. He has an
existing walkway of 4x6x1" (roughly) bricks laid on top of a concrete
walkway. He wants to add a 5'x5' addition to this and had started out
trying to put the bricks on a sand bed then was going to mortar them. I
suggested that the mortar would crack in this case and he should put them
on a concrete pad, then mortar them.

I think real bricklayers could put the bricks directly on the wet concrete
and have them look good (herringbond pattern) but this is beyond my
capabilities, I think. I'd rather have the concrete cured then add the
bricks in a mortar bed or thinset.

Will thinset work in an exterior application?

If mortar is better, how thick should the mortar bed be (on top of the concrete)

I do remember that mortar can stain bricks, so what the best way to mortar
the joints after the base has set up? Or is this done and finished with
the original mortar bed?

This will only have foot traffic so is a 3" concrete pad ok? If we put
steel in, it will be a 4"x4" mesh probably.

--
charles