Storage, Delivery & Handling
Plasterboard must be kept dry and should be stacked clear of the floor using supports not more than 600mm apart as shown in Figure 1. If outdoor storage is unavoidable, plasterboard and accessories should be fully protected from the weather. Plasterboard that has been exposed to direct sunlight, or has been fixed and left standing unpainted for long periods, may become discoloured. If this happens, it must be sealed with a stain sealer undercoat as recommended by the paint manufacturer.
Reduce the possibility of damage to plasterboard, arrange delivery to site immediately before installation. During delivery, care should be taken not to damage recessed edges.
Exposure to excessive humidity during storage can result in plasterboard becoming damp and soft, and may appear defective. In this case allow the plasterboard to dry out and handle with care during installation.
- Avoid open sources of water such as wet floors
- Wrap the plasterboard with plastic overnight
- Provide ventilation
- Install soon after delivery
- Install during dry weather for best results.
Figure 1
Storage of plasterboard
Condensation & Ventilation
Plasterboard must not be installed until the building is weatherproof, particularly in coastal areas subject to sea spray. Complete all exterior doors, walls, windows and the roof before installing plasterboard. Prevent rain from entering buildings, avoid water on floors or other sources of open water and allow wet concrete or masonry to dry. These precautions will reduce excessive humidity that may be absorbed by timber or unpainted plasterboard and minimise defects caused by timber shrinkage or moist plasterboard.
Condensation of water onto either the face or back of the plasterboard must be avoided. Insufficient protection from condensation can result in joint distortion, plasterboard sagging, mould growth and fastener popping.
Many inter-related factors must be taken into account to control condensation. Good practice is to make use of wall and ceiling insulation, vapour barriers, and especially ventilation. Ventilation must be considered for the spaces in walls, under floors and in particular under roofs.
Figure 2
Condensation & ventilation
- Use WaterShield, SafeShield, or MultiShield to increase protection against moisture.
- Use moisture barriers or sarking. However, it is important that the right type is selected for the construction type and that it is installed correctly. [refer to the manufacturer’s specifications]
- Use foil backed insulation under metal roofs as they are susceptible to forming condensation.
- Install eave and gable vents or roof ventilators in the roof cavity. [as shown in figure 2]
- Remove humidity from bathrooms via an exhaust fan to the outside.
- In hot and humid climates where the building is air-conditioned below the dew point of the outside air, the wall and ceiling framing members and internal linings should be fully protected by moisture barriers to separate them from the humid external air. The moisture barriers should be thermally insulated to maintain them at a temperature above the dew point.
- Use a quality paint system to provide protection against paint peeling and condensation soaking into plasterboard and compounds.
External Ceilings
External ceilings are subjected to harsher conditions than internal ceilings, therefore they must be protected from the weather as specified in this section. This extra protection is designed to control the major causes of external ceiling faults which are:
- Water condensing on top of the plasterboard
- Water condensing on framing or roofing and dripping down onto the plasterboard
- Water penetrating the paint system.
Minimum conditions to use plasterboard in ceilings for alfresco areas, carports, balconies and breezeways |
| The plasterboard and compounds will not be subjected to any direct water, long periods of high humidity, sea spray or damp conditions. |
| Minimum 100mm clearance from external ceiling lining to lower edge of verandah beam or masonry lintel, otherwise provide protection against wind blown rain. |
| The plasterboard framing must be designed for the appropriate wind loading conditions. |
| The cavity above the plasterboard ceiling must have cross ventilation. [REFER TO CONDENSATION AND VENTILATION] |
| Sarking and thermal insulation must be used to improve temperature control, reduce wind pressure and control condensation. |
| Installation requirements for external ceilings |
| Use either 10mm SpanShield, 13mm MastaShield, 10mm SoundShield, 13mm SoundShield, 13mm FireShield, 16mm FireShield or 13mm ImpactShield. |
| For improved water resistance, use either 13mm WaterShield, 13mm MultiShield or 13mm QuadShield. |
| Ceiling framing at maximum 450mm centres. |
| Use thermal insulation directly above the plasterboard. This will minimise the temperature difference between the plasterboard and outside air, limiting ceiling sag and mould formation by reducing condensation on the plasterboard. |
| Fix the ceiling sheets using the ‘Screw Only Method’. Nails are not permitted in the installation. [REFER TO SECTION 4.4.1 FOR CEILING INSTALLATION] Additional screws may be required for high wind areas. |
| Provide additional framing around perimeter by inserting trimmers between ceiling frames or installing steel angle [REFER TO FIGURES 3 and 4]. |
| Fix the perimeter of the sheets using screws at 300mm maximum spacing. |
| Install control joints in at 6m maximum intervals. |
| Back-block all plasterboard joints. |
| Set joints using two coats of MastaBase or MastaLongset and a Knauf finish coat. |
| Roll or brush on a high quality sealer undercoat designed for exterior use. |
| Use a premium exterior paint system that includes a mould inhibitor. |
| Plasterboard must not be installed in eaves, or as exterior cladding. |
Garage Ceilings
Garage ceilings are subject to conditions that are more demanding than in other parts of the home. This is the case even when garages are located under the same roof as the rest of the home. Garages have large doors that when open let in rain and strong wind, cars are garaged wet, and they are not normally heated spaces. These factors call for a more durable installation to avoid future maintenance issues.
| Minimum conditions to use plasterboard in garage ceilings |
| The plasterboard framing must be designed for the appropriate wind loading conditions. |
| The cavity above the plasterboard ceiling must have cross ventilation. [REFER TO CONDENSATION AND VENTILATION] |
| Installation requirements for garage ceilings |
| Fix the ceiling sheets using the ‘Screw Only Method’ or the ‘One Third Fixing Method’ [REFER TO SECTION 4.4.1 FOR CEILING INSTALLATION] |
| Provide additional framing around perimeter by inserting trimmers between ceiling frames or installing steel angle [REFER TO FIGURES 3 and 4]. |
| Fix the perimeter of the sheets using screws at 300mm maximum spacing. |
| Avoid windy conditions during and immediately after installation to ensure adhesive sets intact. |
| Back-block all plasterboard joints. |
| Roll or brush on a high quality sealer undercoat designed for exterior use. |
| Use a premium exterior paint system that includes a mould inhibitor. |
Exposure to High Humidity
Ceilings in rooms such as indoor swimming pools and communal showers are subject to long periods of high relative humidity (above 90%). The use of plasterboard on these ceilings is not guaranteed by Knauf.
WaterShield completely covered with a waterproof membrane complying with AS/NZS 4858:2004 may be used for walls in rooms subject to long periods of high relative humidity. Vertical junctions and wall to floor junctions must also be waterproof [REFER TO SECTION 4.1.4 FOR INSTALLATION OF WET AREAS].
For rooms with intermittent periods of high relative humidity such as bathrooms, WaterShield may be used. In these rooms a source of ventilation is required to enable removal of excess moisture, such as an open window or exhaust fan.
Exposure to Excessive Heat
Plasterboard is an ideal building material for normal ambient temperatures. It is not suitable for long periods at elevated temperatures such as installed near fireplace flues or chimneys. FireShield is no exception. It is designed to slow down a fire, not to resist constant elevated temperatures.
The effect of high temperatures on plasterboard is to chemically dehydrate the core. This process generally begins at around 80°C but can occur at lower temperatures under certain conditions. AS/NZS 2589:2007, Gypsum linings – Application and finishing, states that plasterboard must not be exposed to temperatures above 52°C for prolonged periods.
Heat generating appliances have installation instructions for the correct distances between plasterboard linings and heat sources. The Building Code of Australia (BCA) also has requirements for installation of heating appliances.
Glass or stainless steel splashback
For compliance with AS 5601-2004 Gas Installations.
| Clearance to glass or stainless steel splashback is less than 200mm * |
| No plasterboard product may be used behind a glass or stainless steel splashback without tiles. Any plasterboard may be used if it is behind ceramic tiles of minimum 5mm thickness, although in this case SafeShield is recommended for additional fire and water resistance. |
| Clearance to glass or stainless steel splashback is 200mm or more |
| Any plasterboard product may be used, although SafeShield is recommended for additional fire and water resistance. The wall surface must still be covered with a glass or stainless steel splashback. |
* The minimum clearance from the gas burner to the splashback must be 140mm.