Sarking selection and installation tips for metal roofs
Sarking under residential metal roofs is popular because of the many benefits it delivers for little additional cost
Whether it’s as reflective thermal insulation, a protective second skin against burning embers in a bushfire area or as a way to control condensation, CSR Bradford has a product solution to suit your application.
Selecting the right product for sarking a metal roof:
|Extra heavy duty, polymer and reflective foil laminate
|1.5 x 30m
|1.35 x 30m
|1.35 x 60m
Vapour permeable (especially where ceiling batts >R4.1 are used)
|Highly vapour permeable, medium duty, reinforced non-woven membrane
|1.5 x 50m
|Anti-condensation roofing blanket for all climates
|Bulk insulation roofing blanket bonded to reflective foil sarking for thermal and condensation control
|1.2 x 15m
It is considered good building practice to install roof sarking parallel to the eaves (horizontal roll-out) and affix under the battens to allow water to cascade down the lap joints and provide a drying passage between the sarking and roof sheet. If roof sarking is installed from ridge to gutter (vertical roll-out) over the battens, then the following should be considered:
- Taping of the vertical overlap between roll joins is recommended to seal the side laps to prevent water spillage into the roof cavity and provide draught sealing.
- Sagging of the sarking to facilitate drainage to the gutter is required (but not more than 40mm).
- Sagging of sarking to avoid the sarking contacting the underside of the roof sheet (but not more than 40mm) is recommended to avoid temperature transfer from the roof sheet.
- All joins should be lapped 150mm and to achieve a vapour barrier, all joins, penetrations and discontinuities should be sealed.
- Creation of a continuous air space between the underside of the roof sheet and membrane is recommended to create a drying path when possible.
Please refer to the CSR Bradford installation guidance for sarking under metal roofs. Installation should always be in accordance with AS/NZS4200.2 as a minimum.
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