Case 2

Remedial

Repair/Replacement Guideline

The following guideline is provided to assist in the repair/replace decision making process:

• Consider the age and condition of the roof versus its expected serviceable life given the type of membrane employed.
• Calculate the number of damaged membrane area. If the roof is generally in good condition and if the number is less than about 20%, the roof should be evaluated for repair rather than replacement. Also, keep in mind that the older a roof becomes, the more maintenance it will likely require.
• Determine if there are active leaks and what their source may be. Do not assume the membrane is the leaking cause. Gutters, valleys and flashings are more likely candidates. “False leaks” can be caused by moisture condensation in the attic due to improper ventilation.
• Check the interior of the building, any moisture stains at the false ceiling. Very old, delaminating membane will hold moisture and cause adjacent members to deteriorate even if there are no apparent leaks.
• Press down hard on the membrane with your hand. Sound membrane will not be affected by the pressure. Deteriorated membrane will feel brittle and will crack. Tap on membrane that have fallen out or been removed. A full, deep sound indicates a membrane is in good condition, while a dull thud suggests a membrane in poor condition.

Alternative design – use of inverted roof

In the inverted roof system, a layer of roof covering ( concrete slabs or mineral aggregate ) is laid on top of roof insulation. Waterproofing is provided by a layer of bitumen felt below the roof insulation. The concrete roof paving slabs forms a trafficable terrace. They are laid, open jointed on a filter layer of dry sand or mineral fibre mat. This acts as a bed and filter for the rainwater. The open joints are filled with bitumen sealant. The bitumen sealant provides waterproofing and allowance for thermal expansion at the joints.