Plasterwork is used to provide internal walls and ceilings with a smooth, flat surface suitable for decorating with paint or paper. Plaster also provides sound and thermal insulation as well as protection from fire. Decorative mouldings — a feature of walls and ceilings in many older houses — are also made of plaster and are still available for renovations. There are basically two methods of providing a plaster finish: the traditional one is wet-plastering, while the modern method uses plasterboard and is known as ‘dry-lining’.

Traditional plastering uses a mix of plastering materials and water which is spread with a trowel over the rough background in one, two or even three layers and levelled accordingly. When set, the plaster forms an integral part of the wall or ceiling. The background may be masonry or timber-framed walls and ceilings finished with lath-and-plaster. Laths are thin strips of wood nailed to the timber framework to support plaster, which, forced between the laths, spreads to form nibs that grip on the other side. Traditional plastering takes practice before the plasterer can achieve a smooth, flat surface over a large area. With care, an amateur can produce satisfactory results, provided the right tools and plaster are employed and the work is divided into manageable sections. All-purpose one-coat plasters are now available to make traditional plastering easier for amateurs.

Manufactured boards of paper-covered plaster are widely used to dry-line the walls and ceilings in modern homes and during renovations. Plasterboard obviates the drying-out period required for wet plasters and requires less skill to apply. The large, flat boards are nailed or bonded to walls and ceilings to provide a separate finishing layer. The surface may be decorated directly once the boards are sealed, or covered with a thin coat of finish plaster.

Plaster powder is normally sold in 50kg paper sacks. Smaller sizes, including 2.5kg (51/21b) bags, are available from DIY stores for repair work. It is generally more economical to buy the larger sacks, but this depends on the scale of the work. Try to buy only as much plaster as you need — although it is better to overestimate to allow for wastage and to avoid running out of it at an inconvenient moment.

Store plaster in dry conditions. If it is to be kept in an outbuilding for some time, cover it with plastic sheeting to protect it from moisture. Keep the paper bags off a concrete floor by placing them on boards or plastic sheeting. Open bags are more likely to absorb moisture, which can shorten the setting time and weaken the plaster, so keep an opened bag in a plastic sack sealed with self-adhesive tape. Discard plaster which contains lumps.

Ready-to-use plaster is available in plastic tubs. It can be more expensive to buy, but it is easier for amateurs to use and will keep for a long time, provided the airtight lid is sealed well.