Here is some more clarification. I have a slab floor and attaching a 2x4 ledge with Tapcons into the slab in a corner of my bathroom where the shower was. In the shower area is my on grade slab, which then meets my 2x4 ledge. This ledge then drops down about 6.5 inches into the below grade (currently) cement shower floor. I plan to put Hardie Backer on one side of the ledge, the top of the ledge, and the other end where it drops 6.5 inches into the shower floor. It will be covered with Red Guard and then tiled. I am assuming I need to use fiberglass mesh with thinset on the corners of the ledge where the sides meet the top. Is this correct?
I second the picture request.
Since no one else has said it I will. I think Red Guard sucks. I would not use it as a primary shower pan liner. I would not use it in any change of planes. If I was forced at gun point to use a liquid I would use Mapei's AquaDefence - only because the product has something called Mapeband - a flexible corner band.
I would not use any liquids over thin-set or concrete that is not 28 days old.
I would leave the liquid to cure out a week before floor testing.
I would not use a 2"x4" on the slab. That is juts wrong to begin with.
Like I said before your question is vague. Post a picture.
Is this a barrier free shower build?
What is your primary shower waterproofing?
Do you have a pre-slope?
Are you going to flood test?