My frame base is 3/4" ply on 2x8's on concrete slab.

My question, is do I need to make a pre sloped mortar bed for under my membrane or not? I have seen both ways and I'm not sure in what cases you do or do not need one. I just want to make sure and do it properly, but if its unnecessary...

To clarify, I've seen many case where you just create the wood base, place the membrane on top of that, and then pour your sloped concrete ontop of that.

Thanks in advance!

You always need the liner to be sloped.

Where do the 2x8's fit into the picture?

Welcome Seanie, Hi Kevin,

It's not surprising to us that you've seen many shower pans built wrong without the pre-slope. Happens all the time since most plumbers aren't forced to build em right and there is no enforcement of plumbing codes in many jurisdictions.

Think about it. Where will the water that gets through the tile work go once it's trapped by the membrane? Swamp water anyone?

Jaz