These corner shaping tools are two of the specialist items you must hire or buy if you want the best possible finish

Achieving a smooth finish on the face of a sound wall should be reasonably easy provided you follow each of the steps carefully and use the correct tools. Other areas pose more difficult problems and need special tools and techniques for best results.

The plastered finish around the bottom of a wall should be at right angles to the floor, but because this is not always easy to achieve a special internal angle trowel should be used.

As the skimming coat is applied this can be run along the floor (providing it is reasonably flat) to remove high points and flatten the plaster.

Be careful when doing this not to allow the trowel to dig into the surface and gouge away parts of the drying plaster.

In the same way, once a corner has been formed using retaining boards a final finish can be achieved using an external angle trowel. This should be run down any external corners before the plaster dries, taking care to main­tain the correct angle without dam­aging the corner.

Window and door reveals are also difficult to form accurately so a scaf­fold square is essential to guide your work.

This consists of three battens of wood formed into a right angle and can easily be constructed to your own requirements. As the reveal is plastered, push the scaffold square hard against the frame.

You will then be able to see whether the reveal is correctly plastered and be able to avoid high or low points in the finish.

Q My newly applied plaster keeps cracking, I think because the old, porous plaster is drawing the water out of it. Is there a remedy ? A Yes. Mix one part of PVA adhesive with four parts of water. Paint it onto the exposed brickwork and thoroughly soak the edges of the existing plaster. You should hear a 'fizzing' noise as the plaster soaks up the mixture; if not, the mixture is too rich. Apart from forming a water barrier, this treatment helps stiffen the old plaster.