 |
 |
|
As we have read at the beginning of this section on sarking, the membrane is installed under the roof covering and its main purpose is to collect and dispose of any water which may penetrate the roof covering. The Australian Standard AS/NZS 4200.2-1994, which is the standard for "Pliable Building Membranes and Underlays", contains detailed information about how the sarking membrane should be fixed. Great care should be taken to ensure that the sarking membrane is fixed correctly otherwise its effectiveness is limited. Likewise, similar care should be taken not to damage the membrane during fixing. Sarking is laid across the roof rafters with each run overlapping the previous run below it by a minimum of 50 mm. Allow a "one rafter space" overlap where a vertical joint of the membrane is required. To ensure adequate drainage, the sarking should be layed between adjacent rafters and fixed under the tile battens. It should sag no more than the depth of the supporting batten (counter batten) and in no case is the sag to exceed 40 mm. Extend the membrane by about 50 mm over the facia and secure firmly to the top edge of the facia. Make sure that the membrane is extended over the facia enough to ensure effective water run-off. When fixing the sarking at the ridge line, carry the membrane over the ridge board.
| ||||||
