Which Mortar for Bed for One-Piece Maax Fiberglass Shower?

[kailor]

I'll be installing a Maax S-42 one-piece fiberglass shower this weekend (42" x 36"). After dry-fitting the shower into alcove, I want to set the unit in a bed of mortar (not structolite). Which mortar product (by exact name and amount please, if possible) should I use that is readily obtainable from a Big Box Store? This will be on 3/4" plywood subfloor (which I'll reinforce). I have access to both sides of shower, but not back wall. Also, please comment on my plan of attack.

1. Frame alcove, cut area in subfloor for drain
2. With unit on its side, determine approximate depth of mortar bed
3. Dry-fit unit, level unit, mark lines, locate shim areas, etc.
4. Roofing felt on plywood subfloor
5. Apply mortar bed on roofing felt
6. Apply 3-mil plastic over mortar bed
7. Set unit
8. Level/plumb as I screw nailing (oxymoron) flanges to studs (back top flange, side top flanges, front verticle flanges, in that order)
9. Allow to cure

Thanks in advance,
Keith

 

[Terry]

It's impossible to measure and place the correct thickness of the mortar bed.
We place piles of mortar down and very quickly set the tub down, squishing the piles down. All you need is a few points of contact.
The mortar sets up quick, so don't think too long once the piles of mortar are in place!

 

[Sponsor]

 

[kailor]

What product should I use for the bed itself?

 

[Reach4]

Quikrete 110260 should be fine.

 

[kailor]

Thanks. I understand now. A 60 lb. bag of Quikrete #1102.

 

[ShowerDude]

Common concrete knowledge, many mixes contain hydraulic cements that expand as they cure.

minimal yes ......but expand indeed.