In many older homes constructed before the 1930s, ceilings and internal walls are usually constructed of lath and plaster.
Laths are thin wooden strips which are nailed across the ceiling joists or studs of internal walls. Small gaps are left between the laths. The gaps then form a key to hold and support the plaster as it is applied over the laths – as the plasterer applied the wet plaster he forces into the gaps so that it mushrooms out on the reverse side.
Over time the plasterwork is liable to crack and come loose from the laths. When this happens chunks of plaster can fall off the ceiling.
The laths may also suffer decay from woodworm, dry rot or damp.
Repairing or renewing a lath and plaster ceiling can be an expensive job, and many property owners now prefer to have the old ceiling removed completely and replaced with plasterboard. However period properties often have elaborate plasterwork moulding and cornices and if it is desired to replace these the services of a skilled plasterer will be required. This is especially necessary for listed buildings.