What causes ceiling laths to bow upwards?

[Gary111]

Hi, i have had some laths under the bath rot, I have removed those, but some of the existing ones are bowed upwards, causing the plaster to pull away.

I'm trying to figure out what causes the bowing?
The rotted laths were still flat so I'm guessing it's not the moisture?
Thanks

 

[Deleted member 174758]

Possibly the upper side has absorbed moisture (rot indicates a leak?) and swelled whilst the underside is drier and hasn't

 

[HERTS P&D]

And the word JK is looking for is moisture!



Andy

 

[Deleted member 174758]

Duh! Sneezed. Bloody hay fever...