On closer examination, the whole cat-house is in a pretty precarious state. After the last lot of rain, both cats climbed to the top floor, which dried out first in the sun. But their combined weight tilted the whole thing sideways, posts between floors and all. Amusingly, both cats still climb to the top, and sit or sleep at a funny angle, and seem to be blissfully unaware their tower is on its way down. What a scream! I took a picture of it, it's so funny!
So now I've got the job of renovating the framework of the whole thing.... It's always the same, you go to do a little job and it turns out to be rather more than you expected. Worked on some basic frames for each floor today, so if it's fine tomorrow we shall be dismantling Faulty Cat Towers and hopefully strengthening it all up. I might even be able to put up before and after pictures - what a laugh!