Plasterboard - cutting and fixing

Plasterboard types

Wallboard or plasterboard is a flat seam of gypsum, sandwiched between stiff lining paper. It comes in several types and sizes and is ideal for timber framed buildings, loft conversions, stud-partitions and ceilings. The most common size is 2.4m by 1.2m and is grey surfaced, for plastering, or ivory faced, which can be painted or decorated directly.

Ivory boards may have tapered edges so the joints can be flush filled. The boards are available in thickness of 9.5mm or 12.7mm. Boards measuring 900mm x 1200mm and 1800mm x 1200mm are commonly stocked. Longer lengths can be ordered.

Plasterboard and wallboard is available with a vapour barrier, a thin metallic, tinfoil-like backing. These are used in timber framed buildings and as a sheathing where moisture could be present.

There are boards for other uses but these are specialised and have to be ordered:

Duraline - Impact protection - Mustard colour surface
Soundbloc - Sound insulation - Blue colour surface
M.R Board - Moisture resistant - Silicone green liner
Fireline - Fire resistant - Pink colour surface

Measuring cutting and scribing plasterboard

To cut plasterboard to size ...

Measure the opening at the top and the bottom

Transfer the measurements to the face side of the plasterboard.

Hold a straight edge on the measurements marked

Using a trimming knife, run the blade down the edge of the straight edge, cutting through the layer of lining paper and into the gypsum.

Stand the sheet on its edge and snap it at the cut.

Fold on the cut and run the knife up the fold from the other side, cutting the backing paper.

To scribe plasterboard

This is when you have to fit a board into an uneven opening.

Measure the opening at its widest point.

Cut the plasterboard parallel at this width.

Hold the cut edge of the board, plumb and inline with the opening at its narrowest point.

Using a small block of wood the same width as the widest point of the opening as a gauge, scribe a pencil line down the board parallel to the wall.

Cut on this line. Fit the board up against the opening. If needed, trim any proud bits by using the edge of an old saw as a file. In some cases you may have to use a saw, or in extreme cases a pad saw, when the line of the cut is not straight enough to use a trimming knife.

When using a trimming knife, wear work gloves, and, as always when cutting, cut away from the body.

Fixing boards to Studwork

When nailing plasterboard, use purpose made plasterboard nails - these are galvanised or zinc coated, round head nails. They will not rust and spoil the décor at a later date. Always give them that last tap, to ensure they dimple the surface of the plasterboard. This is to prevent them catching the edge of the float and to allow plaster coverage.

You can also use plasterboard or drywall screws. Although moderately more expensive, they tend to hold the board more firmly. This is particularly helpful when boarding both sides of a stud wall, where hammering the second side might loosen the nails on the first side.

General sizes are 30mm for 9.5mm boards and 40mm for 12.7mm boards. Nail at approx 150mm centres.

As usual, check that no pipes, cables or other services run behing the proposed fixing points.

In order to lift plasterboards firmly against a ceiling make a foot lever. Nail a piece of 50mm x 25mm to a 20mm dowel so that the dowel forms a fulcrum for the flat piece to rock on.

When the sheet is in place, tilt it up and push one end of the lever under the bottom edge. Press down firmly on the other end with your foot and the sheet will lift tight up to the ceiling. Nail in position.

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