My house was built during the war by the Post Master General and incorporates what looks like a bomb shelter inside which has been filled in.... I cant think of it being anything else and am quite happy for it to continue to "not exist".... however, I want to be sure that the new bathroom I am building is absolutely water tight.
The external walls are 400mm solid engineering brick with no cavity, stripped back to bare brick.
With exception of one wall being block with a lime mix render, plaster, plaster skim, and paint, the internal walls are brand new bare block construction.
There are 2 bathrooms to address, tiled top to bottom, in windowless rooms, but with so much going on, I'll just stick to one room at a time for now!
I'll start with the "bomb" room which is currently completely bare, not even any plumbing yet.
The area used to be an oversized 1800 x 3000 hallway which I have built a block wall the make it into another room. That new wall is directly over the shelter doorway lintel so more than safe!
The Floor. The area is literally the covered-in steps down to the shelter which has been filled in with rubble, a DPM sheet inserted and then a really rough deep concrete slab on top. The original hardwood framing is still around the edges with the iron railings cut off to ground level.
Would I be correct to seal the floor with 1:1 mix SBR, level it with Mapei Ultraplan 3240 Fibre reinforced compound, then use a liquid waterproofing barrier prior to tiling? This room will have bath with a shower over it at the end, the other room will have a walk in shower.
The 3 sides of the bath/shower area are all different...bare brick at the shower end, rendered and painted wall at the other end, and studded block wall to the long side of the bath with all the pipework in it. Do you think I should just invest in simply covering the studwork and bare brick with something like Marmox insulated tile backer board, or am I skipping a step here? ... do I marmox the brick wall, and cement board/liquid membrane the stud wall? What should I do with the painted wall? Simply heavily key it to get the paint and any extra skim layer of plaster off, add some extra liquid membrane over the keyed "wet area" and tile it?
The new block wall in non wet area could be just scratch coat rendered and tiled, however, with the nature of this house, I really want to avoid any issue with moisture so I’m looking for advice on the best way to deal with this.