This is one of the most important trades as it provides both the finishing standard to the interior of your new home and, where the outside is rendered, provides the final weathering coat.
Internally the choice, for self builders, is whether to opt for hard plaster (a sand and cement render coat with smooth plaster finish) or dry lining (a plasterboard finish). In the past, this choice was often dictated by whether the home was built using traditional masonry construction or was timber framed.
Timber framed properties can only be dry lined but those using building traditional masonry construction have the choice and increasingly, they are opting for dry lining.
Hard plaster requires one, sometimes two coats of sand and cement render with a finishing coat of smooth plaster. The sand and cement render can be replaced by proprietary plasters of differing types, each one of which is formulated for use with a different substrate. The advantage of hard plaster is that it is extremely durable. The principal disadvantage is that it puts enormous amounts of water into the structure, and this can lead to long drying out times.
Dry lining uses plasterboard fixed to the walls and is, therefore, a relatively dry process, which can be decorated shortly after completion. With a timber framed home the plasterboard is tacked directly to the timber studs. When used in traditional masonry construction, it can either be stuck to the walls by means of dabs of plaster or tacked to battening, firmly fixed to the substrate. Dry lining can be taped and jointed using special paper tape, or it can be skim coated with a thin coat of plaster to provide a surface finish that is indistinguishable from hard plaster.
The standard plasterboard can be replaced by the more durable Gypsum Fibre Boards, which provide greater sound insulation properties and are strong enough to take fixings directly.
Ceilings to be Artexed are usually tacked with plasterboard and taped with paper scrim prior to the finish being applied from the floor using special applicators and patterning tools. Any decorative mouldings or covings are put up before the Artex is applied. Plastered, or ‘set', ceilings are jointed with a silk scrim and then finished with a thin coat of smooth plaster. This is applied by a hand held trowel, and there is therefore the need for a ‘board or foot scaffold'. Any decorative mouldings or covings are put up afterwards.
If a floor is to be screeded, it is the job of the plasterer. A screed can be mixed on site from sharp sand and cement, or it can be brought in ready mixed in truck loads. Screeds that are bonded directly onto an oversite or concrete base can be as thin as 50mm. Those that are laid on top of insulation have to have a minimum thickness of 65mm. Screeded garage floors have to have reinforcement mesh within them.
It is also the plasterer's job to render the outside of a building. This means that an independent scaffold should be employed if you are not to incur heavy charges for moving and altering the scaffold.
Rendering is normally carried out with a one or two, occasionally three, coat render of sand and cement. For a smooth finish, the final coat is rubbed up with a float or trowel. Pebbledash is created by thickening the final coat and then dashing (throwing) pebbles into the mixture and pushing them home with a trowel. Tyrolean is created by a handheld machine that dashes a mixture of pebbles and render onto a first coat of render.