Bathroom waterproof membrane question

[MassiveJim]

Just thinking of a future project and would like to call on other peoples knowledge

Our en suite has a freestanding bath that will need replacing and the tiles under it will also need replacing, however I am planning on keeping the tiles on the wall.
The mrs has a habit of spilling loads of water on the floor though, sometimes she remembers to put a towel down but not always

My question is, is there any point putting a waterproof membrane on the floor without creating a "lip" that would normally go up the wall before fitting tiles ?

Is there any other option to help with the situation ?
There is a stain on the ceiling below right around the bath area.

 

[MassiveJim]

its a fully tiled floor and a flat bottomed freestanding bath, as far as I can tell the bath is siliconed to the floor but there is some movement
I think the bath has been in around 20 years,

as far as the water, its just overspill from moving around in the bath, and sometimes quite a lot of water spills out then just sits on the tiled floor until she gets out and mops it up.


EDIT found a picture of the bathroom on rightmove from before we moved in

 

[MassiveJim]

I'm not concerned about the stain on the ceiling, it hasn't got any bigger in the last 4 weeks, I just want to try and prevent the future floor from getting water damaged (currently that step is chipboard with tiles directly on top of it.

Do it properly and remove that step.

We'll keep the step, mainly because we actually like it, but also means I won't need to retile the entire bathroom in doing so.


I've already retiles the floor in the lower part of the room but I broke quite a few wall tiles removing the old floor, so I'm going to have to be super careful on the step because I've used up most of the spare wall tiles

 

[MassiveJim]

it's not like its a major life changing problem, but I'm thinking ahead, when I relay the part of the floor with the bath on it, it would make sense to add some additional level of water protection as a precaution

 

[MassiveJim]

Doesn't matter if they're made of the most water impervious material on earth if water is getting through where the supply and waste pipes come through the floor. Make sure they're sealed, and then as well when the bath is put down, put a fat perimeter of silicone under the tub too.

Overboard the existing floor with tile.backers like marmox, these are fully waterproof. Use a product like marmox multi bond or just silicone when laying them on the joints and finish with the waterproof tape. You now have a fully waterproof floor.

If existing subfloor is wet or is water damaged then replace with some ply before overboarding with the marmox.

When the time comes, the toilet and bath will be replaced along with the floor mounted taps.
the existing floor (step) doesn't feel particularly secure so I fully expect to have to remove not only the floor but the timbers it is rested on as well and possibly the floorboards that they are rested on.
Most work carried out for the original owners of this house is a bit crap so I'm having to correct it as I work in each room.