A reader's General Construction question: Topping, waterproofing?

Mark Mc.   from   Logan, Australia   had this Topping waterproofing question.

I'm doing a bathroom reno and my google search led me to your bathroom renovation pages. This is a very informative site and is what I am referring to most with the unfamiliar jobs I'm doing; namely topping, waterproofing and tiling. My main question is how long after the mortar base is laid, can you apply the waterproofing? Many thanks for the info already posted.

Bill's reply

Hi Mark,
Sometimes you do the waterproofing first and then the topping for the floor falls, but most times it goes in after.

We don't wait too long, 24 hours between normally. Read the manufacturer's instructions just in case.
The topping is usually not too thick, and is either extremely dry, (low water-cement ratio) or it has additives to give it high early strength.

Add to that, the fact that the waterproofing membrane is water based, and has flexibility in it and there is no need for a long drying time.

These products are designed with renovations in mind, so mostly you can't afford to wait what would be a normal drying time. Same with starting to lay the tiles after, start the day after the last coat has gone on.