Lime plaster in three coats
We use lime plaster on most interior walls. It takes three coats and about three weeks, and it is the cheapest way we know to make a room feel calm.
By Freja Lindqvist. . 2 minute read.
Paint sits on a wall. Lime becomes the wall. That difference is the reason we use it, and it is also the reason it takes longer.
What it is
Lime plaster is slaked lime, sand and water, sometimes with a little chopped fibre. It is applied wet and hardens by taking carbon dioxide from the air, which is slow and is why it needs patience. A good plasterer does three coats:
- A scratch coat, 8 to 10 millimetres, scored with a comb so the next coat holds.
- A second coat, 6 to 8 millimetres, levelled with a straight edge.
- A finish coat, 2 to 3 millimetres, trowelled and then burnished with a steel trowel as it begins to set.
Each coat has to dry for several days. In a house that is a cold winter, the schedule runs to three weeks.
What it does
Lime plaster is open to vapour, so a room stays drier. It takes up a little humidity and gives it back. It is mildly antiseptic, and it does not crack at the corners the way gypsum does.
It also does something that is hard to specify: it catches the light unevenly. A wall painted in a flat colour is a flat colour. A lime wall has a depth that comes from the burnishing, and from the grains of sand just under the surface.
What it costs
On a typical house wall, lime costs about twice as much as a painted gypsum board finish, and takes about three times as long. The difference is in labour, not in material. For that reason we use it where people look and touch, and use board where they do not.
What we ask of the client
We ask clients to visit a wall in progress and put a hand on it. Most people say yes to lime after that. The ones who say no usually say it is because they want a perfectly flat white, and we are honest with them that lime will not give them one.