Ask Barry Section

Barry says, the problem with holes in plaster is that they tend to be the centre of weaknesses in the bond between wall and plaster. This means that simple filling often just delays the inevitable....... a whopping great chunk of plaster coming adrift.

Before doing ANYTHING, tap the surrounding plaster. If it sounds hollow, then it is already blown and needs to be excised.

The best filler, then, is to use your regular plaster.

The easiest method, to ensure a smooth filling, without bulges, is to prepare the widened hole with PVA glue. Brush it into the wall fabric and leave overnight. This ensures that the new plaster will have a good key. The PVA minimises the ability of the wall fabric to dry the new plaster too quickly (which is what causes blowing in the first place).

Apply the filling in two stages. First apply a stiff mixture to the wall, not quite out to the level of the existing plaster.

Second, using a plasterer's trowel, apply a thin mixture of plaster to the first layer. Now take a long stiff straight-edge (a length of 4x1/2" wood, or a purpose made aluminium straight-edge) and, with short strokes, left to right and working from the bottom, smooth the second layer of plaster.

THEN

Once the top coat is dry but still soft, use the plasterer's trowel, well dampened, to buff the plaster into a smooth finish.