Consistent with our general mission, we are using traditional construction methods in our basement improvement project. In its present configuration, our basement is in fact largely a product of the twentieth century, when it was rebuilt to accommodate bank strongrooms, with the Robert Adam building propped up above; so some of the ceilings are made of modern plasterboard, but others are lath and plaster, and where these need to be repaired we are using like-for-like materials and techniques.
Laths are narrow strips of wood nailed across ceiling joists (or wall studs) and then plastered, the laths forming a key for the plaster. In the Georgian period, horsehair was often added to the plaster to help it bind to the laths and although we haven't used horsehair on this occasion in the basement, we have done so recently in our ground floor rooms. Laths are rarely used at all nowadays, having generally been replaced by cheaper plasterboard or drywall, but they do offer greater flexibility and tolerance of stress.
Broken laths awaiting replacement (above).
Bundles of new laths (left).