Yaaay, I found another thing wrong with the house! This one isn't getting fixed though.
Basically, while prepping to stick some aluminium angle along the edge of the shower cavity to try to stop water spilling out (it isn't a proper lipless shower, it was very clearly DIY retiled at some point and the tiles sit higher than the original flooring, plus the main floor has no drain at all) I had to get the hair dryer to actually dry along the edge of the shower.
I bumped a tile on the corner while checking the fit of my corner piece, and the tile just... popped off.
The adhesive underneath literally looks like mud and feels wet. I had to point the hair dryer at it for a solid 30 minutes to get it dry enough for some waterproof epoxy to stick to it, so I could stick the tile back down. I would have taken photos, but I was more worried about getting the tile back on.
I'm going to guess at a bunch of the issues...
1) The entire bathroom has never been waterproofed, ever. Or at least, I can see no evidence of any kind of waterproofing under all the peeling paint. It's possible it doesn't go up that high, but I'd bet then that it's probably membrane only, and has either degraded or been punctured in multiple places.
2) The ventilation is basically just the window, through which we use a tiny floor heater (in fan mode) to force extra air in. I'm not convinced that the ceiling vent achieves anything, but I am amazed that in *checks notes* something like 55+ years and multiple renovations, nobody has ever bothered to install a ceiling exhaust fan.
3) Whoever did the shower cavity tiling was not a tiler, did not consult any form of guidance or ask at any counters, and probably used the incorrect tile adhesive or tried to use grout as tile adhesive.
4) Thanks to all of this, the shower floor under the tiles has basically been permanently saturated, and I guess actually drying the floor out near the edge made the tile adhesive let go on that one tile.
I'm not fixing it though. Firstly, it's just too expensive and too much work.
Secondly, I'm pretty sure that properly addressing the ventilation issue is out of my hands, because to install a ventilation fan in a room that's never had one before would definitely be a job involving a qualified electrician.
Thirdly, I need to be able to shower at least every couple of days, and I think this would be a lot more than a two day job.
But it's mostly the cost and the part where this isn't even my house (and I haven't even got so much as a 'thank you for addressing so many issues yourself' for any of the work I've done on it, or an apology for how filthy the place was when I got here). It's a level of work that I don't want to do without some serious compensation.
But it also annoys the hell out of me, for reasons that are probably mostly a combination of The Tisms and growing up in shitty rentals where nothing ever got fixed, we were never allowed to even try to fix anything, and yet it was also always our fault.