Waterproof a Laundry Room?

I would like to know how to waterproof a Laundry Room floor that I am going to tile. I am using 1/2 " treated plywood over the existing plywood and then using Durock 1/4" or 1/2" which ever you think is better. I need to know where to put the waterproofing and what to use. I have not located a pan that will fit. The laundry room is on the second floor and I have installed a center drain rough in. It measures 8'9" x 4"6".
Thank You,
Stephen Ayers

1/2" hardibacker over the plywood should be sufficient. However, you said waterproof and cement board of any type is NOT. You would have to have a moisture barrier under it, as is done in a shower. A better choice for a floor would be redgard coating, or something from the schluter family.

To ensure the water runs to the drain, you need slope. What you need is essentially a large shower pan with a curb to keep it from running out into the hallway. You could effect a low one with a marble threshold, which MIGHT keep it from running out, depending on the flow rate. Keep in mind, you'll need to run the waterproofing up the wall a little, or it will just run underneath the wall plate. Check out www.johnbridge.com for some additional ideas.

If you have a pan underneath the washer and run the drain line from it, you wouldn't need the slope. This would NOT help (much) if a hose burst, though.

Don't use treated plywood. It can have enough movement (shrinkage) to crack tile. Use a schluter product as is done in a shower.