I second that. For putting down Durock on OSB, you can use the cheapest morter available....try "Customblend" from Homer's. All that is there to do is fill voids and hold the Durock "up." The screws hold it down. If you are tiling over this, then a good modified morter is required. I guess you could use the redguard on top of this but, again, I have no idea of your project.....

@Silverlined Did you all use Kerdi board on shower walls (to eliminate the need for cement board) or kerdi waterproofing membrane over drywall? I ask provided I’m a bit iffy at the thought of including drywall in the mix. The Kerdi board itself is pretty expensive provided I cannot find any business that sells single sheets at a reasonable price, and although both their shower kit and bulk pricing seem more reasonable, the sheet counts/square footage are over twice what I require.

I used cement board and red guard.

Yes, we used Kerdi board, the membrane, and the pre-molded forms and corner blocks. We hired a contractor who had taken Schluter training and was experienced in the application, so they provided the material. Do you have a nearby ProSource? They can get you everything you need to do it yourself if you want. Cement board and RedGuard like the previous poster mentioned is a viable alternative. This was our 2 time to gut that same bathroom to the studs with leakage issues from cement board and plastic liner installations, so we took no chances on doing it right this time.

@mainenell I’m thinking I’ll likely do the same given my project is a hall bath and pricing/sell of Schluter’s products seems geared towards bulk buys. Although, I may use Ditra for the floor.

@Silverlined I’ve not heard of ProSource but will check. Thanks for the tip.