Fan on a Crumbling Walls

We were installing a toilet fan.  Everyone thought it would be straight forward, but it was everything but.  The wall was crumbling, and the previous decorators could not be bother putting it right, so there was no means of fixing the fan.  I was thinking about botching it, but there weren't even enough wall left to botch.


To properly fix it, I would need sand and cement, but since we have not got that and I was not prepared to get a bag of cement just got that, we used the next best thing, poly filler.  I started out just gluing bits together, then I decided to build it out properly.  I built it out and let it cure.


When we come to fit the fan, it was very snug.  We had to trim out the poly filler.  We still cannot fit the fixings as the wall is now more uneven than before.  It will be another few hours work of work to even out the wall, paint and refit.