Hello everyone.
First of all i don't know if its the right place to post it, but i will try to explain anyway.
I have to do some repairs after torrential rain.
Old house, cavity wall construction with old bricks and lime mortar.
Room is under ground level on 3 walls and last wall there are 3 windows, which are placed on top of a kind of "balcony"(sorry don't know the english word for that kind of stuff!) and 700mm away from those windows theres the concrete retaining walls around them; its basically an escape route trough the windows that goes outside.
Hope i pictured the place properly.
Problem is that with heavy rain, the space between retaining wall and windows (which is tiled now with what i think are terracotta tiles nearly an inch thick ,100*100mm square and very ancient) become like a swimming pool, and since the windows are timber, water is seeping before the "cill" going underneat the tiles and running down the cavity, filling it with water(the air brick underneath was like a tap...).
Good thing is that theres a drain in both corners of the "floor" but since the level isn't sloped toward them they are not working properly.
What i thought was a good idea, after carrying out tests of "seepage" etc etc was to rip old tiles up, take the existing level further down without damaging the drain pipe, and make the level properly, sloping towards the drains.
And here the question, i was thinking to tank it to make it waterproof so water doesnt run under the tiles, unable to reach the cavity.
Is "Mapelastic" the right product to do something like this?
I have used it for years to do balconies and terraces, but not sure if it will work for something that i think work like a swimming pool...
I also noticed theres another product called "mapelastic aquadefence" which seems to be like the mapegum, but i think its less hardwearing than the usual mapelastic.
What do you think about it?
Sorry for the long post, i think mapelastic is the only option but just wanted to see what everyone here think.
Thanks for reading.

sounds like the right approach not sure on the tanking products (someone else will advice on them) just make sure water falls away from the house wall as well

Was the ground outside raised up at any time..do you have any pics.

The state of it was very bad, lifting tiles, no sign of grout at all.it must have been like that for years, since the building is very old.
when i can i will post a photo of the tile, cant of the place because i dont have permission to take photos.

If it's your property might worth getting someone round on the tanking side to advise, maybe more work than meets the eye.