Ceiling collapses can cause serious injury to occupants and damage the contents of the room. Sometimes there are no warning signs that the ceiling is about to fail, it should be expected that once a ceiling is installed it should last the lifetime of the home.
The Building Commission has conducted inspections of homes where large sections of ceilings have collapsed and in all of these circumstances it was noted that the plasterboard ceiling sheeting had not been installed as per AS 2589 and the plasterboard manufacturers specifications. The one constant factor that was in ALL cases was noted to be poor application of adhesive.
The following practices need to be applied and supervised effectively:
Ceiling framing members: On completion the ceiling framing members need to be true and flat, undulations should not exceed 4mm over a 1.8m straight edge. Bowed and twisted joist need to be straightened or replaced. The ends of the joists need to be well secured to minimize any lateral movement. Ensure full edge support around all openings including vents, access hole and air conditioning. Make sure there is no dirt or dust on the joist prior to placement of adhesive.
Fastening systems: Ensure the correct mechanical fasteners are used, AS 2589 states that a 30mm screw is required. The heads of screws or nails are not to be overdriven through the paper of the plasterboard. The adhesive dab needs to be 25mm in diameter and 15mm high, the dab needs to fully spread across the joist and be seen on both sides. Ensure correct placement of adhesive dabs, there should be a minimum of 200mm separation from the fasteners and the board edge with a maximum distance of 230mm centres between adhesive dabs.
Installation of Equipment in the roof space: Manufacturers specify a load of around 2kg per square meter directly onto 10mm thick plasterboard. Air-conditioning and ventilation equipment including flexible ducting is to be fully supported up off the ceiling framing and sheeting. (Refer to AS 4254 2012) Heavy fittings such as ceiling fans and large light fittings are to be supported from the ceiling framing and nnot supported by the plasterboard sheeting.
Perth Property Inspections provides building inspection services to all areas of the greater Perth region. Please call us on our free call number 1800 781 251 if you have any questions or require a building inspection. Visit our website at Perth Property Inspections