Until the early 1990’s, a large proportion of Perth homes used plaster glass for ceilings. These ceilings were fixed to the timber joists through the use of saddle straps. Over time, these straps broke, stretched and failed. This led to ceiling sagging where the ceiling separated from the timber joists.
Ceiling sagging is not exclusive to older homes. Gyprock ceilings can still experience sagging for a variety of reasons. This can include old insulation or not enough fixings to the timber joists.