If the $500 is within your budget and you're unsure of your skills, then the easiest might be to have the "local guy" do a deck mud preslope and drain, install the membrane, and then the tiling base of mud on top of the membrane for the $500.

But only use him if he will do a deck mud preslope BELOW the membrane, so the membrane that then gets placed on top of the preslope will be sloped, resulting in a sloped membrane. If his plan is to install the membrane flat on the floor and then do a sloped deck mud base on top of that, that's a no-go. You need a sloped membrane, not a flat one.

Regardless, if you use him, that's $500.

All you'd have to pony up for is for cement board for the walls; Durock or Wonderboard. Screws to fasten the cement board to the wall studs, and mesh tape to tape the cement board seams. Maybe $100 for everything.

When the cement board is up and the seams are taped and thinsetted, then you can waterproof the cement board with the RedGard that you already have.

Then tile.

Like terricks wrote, if you wanted to use Kerdi over a mud base, you'd need a $75 Kerdi Drain. Deck mud for the sloped pan would be $50-$100 in materials. Just sand and portland cement. I have some photos of Kerdi over a deck mud base on this thread, skip down to about halfway through the thread.

Although I use Kerdi over cement board, you can do Kerdi over regular drywall. There are places that sell Kerdi "by the foot" or even partial rolls. Rolls of Kerdi are a meter wide, or about 39-1/2" wide, partial roll pricing is around $2 a sqft.

Or you buy a whole roll and resell the unused remnant on craigslist or ebay.

There have been hybrid methods, Kerdi floors with RedGard or HydroBan walls, and even Kerdi Drains with HydroBan floors and walls. You need to be careful when going hybrid, in transitioning from one material to another.

Your least expensive build would be to do a deck mud slope on the floor, cement board on the walls, then RedGard the entire thing. You;d need to read up on the RedGard instructions on how to detail the RedGard to the drain. But in this case, you already have the drain and the RedGard, so your only additional expense would be the cement board for the walls, as well as cement board fasteners and mesh tape, and any reinforcing fabric you'd need to embed in the RedGard. Plus the portland and sand for the preslope.

So there are several options, but they're a blend of cost versus DIY ability.

One other thing-- there's no need to get that big a roll of Kerdi unless your shower's going to be a couple hundred square feet. They sell 55 square foot rolls of Kerdi. Another alternative would be to use Kerdi's drain, and use Laticrete's liquid roll on Hydroban waterproofing. Laticrete is the only manufacturer who will warranty this type of "hybrid" (using pieces from two different manufacturers) installation, and I can guarantee you-- the Hydroban will be cheaper than the Kerdi. Alot easier to install, too.

I was going to bring up the HydroBan and Kerdi Drain hybrid thang, but didn't since they already have RedGard.

Bill, has anyone over on JB forums done RG and the KD?

Redguard all the way. I used the standard mud pan, liner, and mud over the liner. Put a vapor barrior between the studs and the hardiboard. Oh yea I used hardiboard. Look at the manufactuers recomentations on installation. Then Redguard. Sleep well it works fine.

Thank you so much for your replies; this is exactly what we needed.

We already have a drain installed by the plumber, so if we were going the HydroBan or RedGuard route, why would we need a Kerdi drain? We're happy with the current drain placement.

I bought RedGuard b/c I could find it locally at HD for a reasonable price ($120 for 3.5gall?). I couldn't find the Hydroban and online it seemed pricey ($76/1 gallon). I am concerned about getting the RedGuard installed to the perfect thickness. I have no idea how one would measure that. The HydroBan sales videos make it look so easy. They are similar products, right?

If you already have a drain installed, then you don't need a Kerdi Drain. And since you already have a drain installed, don't use Kerdi on the floor. Kerdi is designed for use with a Kerdi Drain and not a standard clamping drain.

If you RedGard the walls you don't need a membrane or barrier behind the cement board.

RedGard and HydroBan are similar in that they are both topical liquid membranes.

Both are easy to install, but yes, care needs to be taken so you don't overwork the product once it's on the wall. You don't want to introduce air bubbles which can pop and cause pinholes in the membrane. Paint it on like paint, don't try to to stretch the coverage. Multiple coats will help ensure you get proper mil thickness and no pinholes. You can buy a wet gauge to measure mil thickness, but it's not necessary. Just read and follow the installation and application instructions.

Okay, great. I spent a lot of time a the JB forums last night--thanks soooo much for that advice, too. There is a TON of info over there and we're feeling more confident after your posts and reading there, too. Wish us luck! It might be a crazy couple weeks around here!

Feel free to start a thread at JB Forums on your project. We'd be happy to walk you through any bumps in the road as you progress.....

Bill, has anyone over on JB forums done RG and the KD?

No, because Custom won't warranty it. It HAS to be Hydroban, if you want the warranty coverage.