Floors & Ceilings

Repair of plastered ceilings and reed

Plaster applied over reed, wattle or wooden laths is a building method that has disappeared from modern solutions. In many cases, ceilings have been unnecessarily taken down and replaced due to a lack of understanding and fear of their stability. A good understanding of its construction might save some of these historic building methods.

What is happening?

Defects in laths, reeds or wattle supports will depend on the cause and extent of the failure. The plaster may have collapsed or still be in situ. Detachment and damage can be caused by rot or insects. Most damage is related to water ingress, however, and therefore locally placed. If the plaster has collapsed due to failure of the support, renewal is simpler than local repairs. Cracking is associated with the separation of material from the support. The cause and extent of cracking needs to be evaluated before deciding on the repair method.

Cracks, surface damage and replacement

In the case of cracks, these are filled with an appropriate mix of plaster or render (interior filler gauged with whiting). For surface damage, damaged plaster is removed and reapplied with plaster or lime mortars similar to the original. Be careful when removing the old plaster so not to loosen more material. Following the same procedures as for a solid background, the plaster should be applied in layers to ensure adhesion, strength and graining. Finish with lime. In some cases, a primer needs to be used. Finally, in the case of detached plaster, the procedure needs to be evaluated by a skilled plaster conservator who can select the right technique. A total replacement is the last option. After removing old lath and plaster, new reeds and lath are mounted, nowadays normally in sheets of reed. Then apply new plaster of lime-based mortars on the lath following the same procedures as for a solid background.