Gyprock plasterboard is used as an internal lining board to provide smooth, strong, long-lasting walls and ceilings for homes, offices, hospitals, hostels for the aged, schools, shops and factories. Its durable surface will accept most types of decorative finishing, including paint, wallpaper and texture compounds.

Joints between Gyprock plasterboard sheets are reinforced and concealed to provide a smooth, durable finish to the whole surface. Alternatively, the joints may be covered with a decorative moulding.

Standard Gyprock plasterboard or Gyprock Aquachek can be used for exterior ceilings and eaves lining, provided the ceilings are protected from the weather. Gyprock FLAMECHEKMR plasterboard is fire and moisture resistant. When used in wet areas, installation is in accordance with the Wet Area Installation section of the Residential Installation Guide. When used in fire risk areas, installation is in accordance with the General Installation section of the guide.

Design Considerations.

Levels of Finish

Levels of finish are defined in the Australian/New Zealand Standard AS/NZS 2589.1 : 1997 Gypsum linings in residential and light commercial construction " Application and Finishing. This standard is intended to provide builders, plasterboard installers and finishers, and their customers with the various defined methods and practices necessary to meet the customers expectations in terms of the Level of Finish.

Six Levels of Finish (0, 1, 2, 3, 4 and 5) are defined, and minimum specifications to achieve each level of finish are detailed in the standard for each of the installation processes from framing preparation to finishing. It is essential to determine the level of finish required before the frame construction begins, as specific tolerances are required for frame alignment as well as plasterboard fixing and finishing for each of the levels of finish.

Unless these requirements are met throughout construction, it may not be possible to attain the desired finish level without extensive corrective measures. The level of finish specified also affects the methods of jointing, particularly butt joints and back-blocking requirements, the number of coats of joint compound applied as well as the fitting and finishing of stopping and corner accessories.

It should be noted that, generally, domestic applications should be prepared to a minimum Level 4 Finish unless specifically a higher or lower level of finish is agreed to by all contracting parties.

Fire Resistance

All Gyprock plasterboard is fire resistant to some degree. Gyprock FlamechekMR, however, has been formulated to have even greater performance than standard board. In comparison to 10mm Gyprock plasterboard CD, FlamechekMR was found to be up to 50% better at resisting the effects of fire on walls and ceilings where there were no penetrations or openings. In any case, penetrations and openings can reduce the fire resistance of a system.

Smoke alarms save lives and CSR Gyprock recommends that suitable alarms be installed. Fire extinguishers and fire blankets should also be accessible. Gyprock FlamechekMR cannot be used as a substitute for Fyrchek.

Systems with Fire Resistance Levels incorporating Gyprock Fyrchek plasterboard are presented in the Gyprock Fire & Acoustic Design Guide.

Control Joints

Movement and stresses created by temperature and humidity fluctuation, can result in deformation and damage to internal linings and partitions. It is recommended that Gyprock plasterboard surfaces be isolated from structural elements, except the floor, by the use of control joints or other means where:

• A plasterboard surface abuts any structural element or dissimilar wall or ceiling assembly

• The construction changes within the plane of the partition, wall or ceiling lining

• Control joints incorporated in a building to permit movement in the structure must be carried through all areas lined with Gyprock plasterboard.

Lighting

Any imperfection in a completed lining installation will be made obvious by a condition called critical lighting or glancing light, where the incident light from an artificial or natural light source is nearly parallel to the surface. Glancing light also greatly exaggerates the size of imperfections making them glaringly obvious.

Ways to minimise the effect of critical lighting from artificial lighting sources are:

• Locate fluorescent lights about 450mm below the ceiling, as this will give a more even distribution of light.

• Use more rather than fewer lights and install at regular spacings to give a more even, diffused light and to minimise the shadows that can occur from a single row or single light source.

• Recess light fittings into a ceiling (although recessed lights are more likely to be associated with glare problems).

• Allow a generous angle of incidence to the surface for feature lighting such as spotlights, to minimise the highlighting of imperfections.

• Do not locate a single or isolated unshaded light source close to a wall or ceiling in a space that has generally low levels of light.

• Do not use up lights, wall-washers and spotlights in areas with a smooth wall finish to eliminate light being emitted at a glancing angle to the surface.

• Design soft rather than harsh lighting conditions.

• Do not take window glazing right up to the ceiling level.

• Avoid placing windows immediately adjacent to the end of a wall.

• Provide sunshades over the window.

• Recess the window to stop the sunlight reaching the wall.

The following situations may give rise to localised high temperature conditions (≥45) which may be detrimental to wall and ceiling linings:

• Radiant ceiling heaters,

• Heat pumps,

• Reverse cycle air conditioners,

• Solid fuel stoves.

Applied Finish Selection

Finishes applied to the Gyprock plasterboard can have a significant effect on the perceived quality of the installation, particularly where critical lighting conditions exist.

General rules when selecting the applied finish are:

• The difference in texture and absorption characteristic between the body of the sheet and the joint may show through some thin paint coatings.

• Imperfections show more readily on ceilings than on walls.

• Textured or heavy patterned finishes tend to hide imperfections.

• Matt finishes minimise imperfection visibility.

• Semi-gloss and gloss finishes highlight imperfections.

• Less likely to show imperfections and impact damage.

• More effective at diffusing the light and reducing shadow effects, particularly in smaller rooms.

• Gloss paints tend to highlight paint application variations (e.g. where a good wet edge has not been maintained when painting).

• Paint or thin wallpaper finishes are less tolerant of imperfections.

• Paint applied with a longer pile roller tends to mask imperfections better than those applied with a short pile roller.