Lafarge Plasterboard Australia

1. What is the 'Level of Finish' required for plastering applications?

Level 4 is generally the accepted level of finish for domestic construction. Unless otherwise specified, a Level 4 finish is the default finish for living areas. All plasterboard installation must adhere to AS 2589.1:1997 Gypsum linings in residential and light commercial construction - Application and finishing. Refer to the FWCIANZ Levels of Finish.

2. What is back-blocking?

Back-blocking is the process of reinforcing ceiling joints with cut-to-size pieces of plasterboard adhered across the back of the joint with MastaBlock Back-Blocking Cement. Back-blocking helps prevent joint cracking caused by building movement, especially in large ceiling areas. Back-blocking forms part of the plasterboard lining standard (AS 2589.1:1997), and manufacturers' guarantees/warranties may be void if back-blocking has not been carried out. All back-blocking must be completed before commencing jointing.

3. What substrates can plasterboard be fixed to?

Plasterboard can be fixed to various substrates that form wall partitions, ceilings, bulkheads or ducting arrangements. Plasterboard is most commonly fixed to steel studs, timber studs or masonry for wall partitions. Plasterboard can be fixed to ceilings and/or floor joists by either directly fixing the plasterboard sheets to the joists, or by first installing metal furring channel and then fixing the plasterboard to the furring channel. Furring channel is also used to fix plasterboard linings for suspended ceilings or as an alternate method for fixing plasterboard to masonry on walls. All methods of installation can be found in the General Installation Technical Bulletin.

4. What methods of fixing should I use to install plasterboard?

The Australian Standard AS/NZS 2589.1:1997 allows three ways to fix plasterboard to steel or timber substrates. The options are screw fix only, nail fix only, or a combination of either screw or nail with adhesive. The preferred method is to use screws or nails with adhesive. It is not recommended to use a nail fixed only system on a level 4 finish. Please refer to the General Installation Technical Bulletin or AS/NZS 2589.1:1997 for correct spacing of each method and correct screw/nail type and size.

5. What are the maximum steel/timber framing centres for plasterboard?

Maximum Framing Centres (mm)	Board Thickness	Walls	Ceilings
MastaBoard	10mm	600	450
Span 600	10mm	600	600
MastaBoard	13mm	600	600
MastaBoard	16mm	600	600

6. What is the best way to paint plasterboard once it is installed?

When installed in accordance with Lafarge Plasterboard installation guidelines, the finished surface of all Lafarge plasterboards accept most types of decorative finish: emulsion or oil based paints, stipples, enamels, textured coatings and wall papers. Matt finishes give the best appearance; gloss or sheen finishes tend to highlight any surface irregularities, as will harsh or glancing light. In order to obtain the best finish to the walls Lafarge Plasterboard recommends the following:

• Lay down the nap of any scuffed areas using MastaFinish or MastaMix jointing compounds Surface should be free of dust and other foreign matter
• Ensure that the joint treatment is thoroughly dry before applying the sealer
• Always seal over jointed and unjointed areas Use roller application for paint. Overworking of sealant coat on jointed areas may cause paint to lift. Roller application applies uniform texture over the entire surface
• Use only the best quality paints and other finishes. Use of sealers or undercoats that are water based is preferred to reduce the possibility of raising the paper linerboard nap
• Lightly sand between coats if nap is raised Apply finishes in strict accordance with manufacturers' instructions.

7. How do I finish a plasterboard joint once the sheet has been fixed?

There are only two types of joints formed when installing plasterboard - recessed edge joints or butt joints. The recessed edge joint is formed along the length of the sheets and the butt joint is formed along the width of the sheet. The finishing method is the same for both types of joints, but the width of compound coverage varies. Lafarge Plasterboard recommends the use of paper tape with a three coat compound application: two base coats (or bedding coats) and a third top finishing coat.

8. How often should I install Control Joints?

Control joints must be installed to relieve stresses imposed by structural movement including those due to excessive changes in temperature and humidity. In long, unbroken partitions of wall or extensive ceiling areas, control joints should be placed not more than 12 metres in either direction, and should be aligned with control joints in the structure or intersect doorways, light fixtures, heating vents and air diffusers.

9. What type of plasterboard do I need to use for a Fire Rating?

Only Fireshield, Multishield and GIB Toughline™ can be used in fire rated systems. Please refer to the Fire & Acoustic Technical Bulletin for wall, ceiling, encasement and ducting systems.

10. What type of lining should I use in Wet Areas such as bathrooms and laundries?

Only approved water resistant linings can be used in 'Wet Areas' and these include Watershield and MastaBoard Fibre Cement. Watershield is a water resistant plasterboard whilst MastaBoard Cement is a fibre cement board. Both are suitable for use in Wet Areas. Refer to the Water Resistant Installation Guide.

11. How can I improve the sound performance of the walls in my home for a home theatre system?

To improve the performance of your room, consider the following:

• To help reduce sound transmission through a wall - install an improved sound resistant plasterboard and wall system. Refer to the Soundshield Techncial Bulletin.
• Ensure no gaps or penetrations remain for sound to leak through in a wall by using a sealant. Doorways dramatically decrease the acoustic performance of the room. Even with the door closed, sound can still either flow under the door or still penetrate through the door if the door is of low acoustic performance. Solid core doors are recommended.
• Sound will travel into ceilings and through floors, and be transmitted to other rooms and also areas external to the house.
• Including insulation in the wall cavity between the studs will reduce sound transmission between rooms.
• Resilient mounts or channels can be installed to reduce the level of sound penetrating through the structure.
• Double separated stud walls help to reduce the level of sound penetration through a wall, by helping to de-couple the sound transmission from room to room.

Sound is a 3D pressure wave travelling through the air. It will pass from one room to another by travelling through any part of the structure of the room - walls, ceilings, doors, windows - and any gaps. From these, sound will take the path of least resistance. Therefore, the entire room and surrounding environment play a very important part in achieving the desired results.

Soundshield is a high-density plasterboard useful in resisting the penetration of lower frequency sounds, such as the sound a sub-woofer generates. Combining Soundshield with insulation will help reduce transmission of medium and high frequency sounds, such as people talking and high-pitched sounds. To achieve the best results, combine Soundshield with a Lafarge Plasterboard Acoustic System. Refer to the Soundshield Technical Bulletin.

For high performance and specialist requirements Lafarge Plasterboard recommends consultation with an acoustic engineer during specification.