The question often arises…should a plasterboard ceiling in a home be fixed directly to the underside of the roof trusses or floor joists, or should it be battened?
The Australian Standard AS/NZS2589 provides the requirements for the application and finishing of Gypsum linings in residential and commercial applications, and therefore is an appropriate starting point. Per the standard, Level 4, is the recommended general standard of finish unless prevailing conditions require otherwise, which can be accessed via the matrix provided in the standard.
Whilst the standard provides a whole raft of information around the application and finishing of gypsum linings, the fundamental principle is to ensure an acceptable level of finish is achieved and all parties agree on the expected outcomes.
Some of the more obvious criteria to consider:
- Materials of construction
- Acceptable deflection limits
- Critical lighting
- Heating, ventilation and ambient conditions
- Application – ceiling under floor, ceiling under roof etc.
All materials expand and contract due to changes in temperature; however some materials will also expand and contract due to changes in moisture (humidity) as well. It is reasonable then to match materials based on their expansion/contraction rates, or conversely separate materials when close compatibility cannot be achieved.
For this reason it is important to understand the materials of construction, and their compatibility requirements.
It is unreasonable and cost prohibitive to construct dwellings that do not move, when subjected to imposed loads, apart from the fact this may not always provide an acceptable solution.
Once we accept the building must move, it is then necessary to ensure the linings covering the structural frame can accommodate the expected movement or are appropriately isolated from this movement. Isolation is best handled by providing secondary framing members, capable of accommodating the structural movement, whilst maintaining adequate support for the linings.
The above commentary covers a very, very small portion of the factors which can ultimately determine the performance, or lack thereof, of the ceiling system. In reality, it is not possible to sit down and contemplate every possible scenario for every single project and accordingly it is best to rationalise back to a system which provides the lowest possible risk of failure at a reasonable cost.
For this reason, Rondo recommends that all ceilings in residential dwellings be battened out prior to installing the linings. Rondo provides several options of battens which when installed in accordance with our recommendations will provide an acceptable solution for normal residential construction. Furthermore, Rondo can provide design alternatives for those more complex or challenging projects.