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Building? How to choose the right ceiling insulation

There is no user manual for all aspects of homeownership, from moving, to taking occupation and to maintaining and understanding common and uncommon defects. Albert van Wyk has more than 38 years’ worth of building experience and has put all he has learned into a concise, easy-to-use reference book entitled, The Proud Home Owner. He has granted HomeTimes exclusive access to republish portions of his book to help homeowners make better decisions around buying and selling, as well as maintaining their properties.


For standard ceilings 6,4mm thick boards with H-strips are used to join the boards. Brandering (38mm x 38mm timber) is nailed on the bottom of the roof trusses on which the ceiling boards are fixed. The spacing between the strips should be between 400mm and 450mm. The boards could sag when the spacing is bigger.

Suspended ceilings are installed on a metal frame work below a concrete slab when it is not practical to plaster the concrete slab or to create bulkheads.

For a smooth plastered finish, 9mm-thick boards must be used and a fibre tape should be applied over the joints, before a thin coat of Rhinolite is applied.

Ceiling insulationfibreglass insulation

This has to be installed as it is now a legal requirement and it is part of the energy saving regulations. The specification for this will be indicated on the plan and you only have to make sure that the correct product is installed.

Fibre glass products

It is available in different thicknesses: 50mm to 135mm in rolls of about 900mm wide. It will be worth the effort to look on the ceiling boards after all of the product has been spread open, because I have found that unscrupulous contractors just leave the rolls of fibreglass insulation on the ceiling.

roll of fibreglass insulationThe fibreglass sheets should not be laid over the LV transformer because it will get too hot.

Cellulose fibre

It is made of recycled materials and is 100% fire retardant, insect and rodent resistant. The product is delivered to the site in bags and then air is blown into it, or it is manually spread open on top of the ceiling boards to the required thickness.

Extruded polystyrene

The product (Isoboard) is available in sheets of different thickness, between 25mm and 80mm and in long lengths. It is suitable for extra insulation under the surface bed and can be used as a ceiling board with little or no extra insulation on top.


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