Surface - Plasterboard

Plasterboard is used to line interior ceilings and walls. Plasterboard is commonly referred to as Gyprock, although this is simply a well-known brand of Australian plasterboard.

Standard plasterboard is made by sandwiching a layer of gypsum plaster between two thick sheets of paper. Plasterboard is a very porous, moisture hungry substrate that has a tendency to suck moisture from the coating applied to it. An appropriate prepcoat is used to aid adhesion of topcoats and seal off porosity. If not, the gloss level, colour uniformity and texture of the finish will be affected. 

When a customer is painting plasterboard, they’re actually painting two different substrates; plasterboard and plaster. Plaster is the white, cement like material used to ‘set’ joints and cover screw heads. The main objective for prepcoating plasterboard is to turn two different surfaces into one uniform, continuous surface. The most effective way of achieving this is through the use of a quality acrylic sealer undercoat, and the introduction of surface texture by using a roller (stipple).

All surfaces must be clean, set and dry prior to painting, including jointing compounds. The plasterer must sand the final coat of plaster with a fine 180 to 360 grit sandpaper, leaving the surface smooth and flat. If needed, also lightly sand the paper surfaces to remove any minor surface defects. Sweep plasterboard with a soft brush, broom or tac cloth to remove dust prior to painting.

The following accessories can be recommended for plasterboard paint projects:

• Hand Sander
• Pole Sander
• Duster Brush
• 180 - 360 Grit Sandpaper
• Medium Fine Sanding Block
• 10mm to 15mm Nap Roller
• Plaster Base coat
• Plaster Top coat
• Filling Blades
• Mesh Tape
• Dust Masks
• Rags
• Goggles
• Gloves
• Step Ladder

For a premium finish, de-nibbing (light sanding) following application of the prepcoat with a 180 to 360 grit sandpaper will allow for a higher-quality topcoat texture. Dust down the surface before applying the topcoat. 

The application of the sealer is essential in preparing the plasterboard and jointing compound surfaces for the next two coats of paint by equalizing the porosity of the surface and reducing the suction rate. The sealer should be applied as soon as the plasterboard joints are set and dry as the joints will be susceptible to re-absorbing moisture from the surrounding environment if left unsealed. 

If left unpainted for some time, the paper face of the plasterboard will yellow which can cause bleed-through problems for the topcoat. Where yellowing has occurred, an oil-based sealer binder should be recommended as a prepcoat.

A quality acrylic sealer undercoat is recommended. 

* Suitable for spray only, used as a high-build surfacing coat, to be overcoated with a quality acrylic sealer undercoat.

A quality, 100% acrylic topcoat is recommended.

This table is a guide only, there are many other products offered by a variety of brands that may also be suitable.

* For use on ceilings only.