The minimum pitch for rooflights is 3 degrees. This is enough to ensure that water will drain off the surface of the glass and avoid ponding. Glass inherently has a degree of flex when installed flat, known as ‘deflection’ and means that without pitching the rooflight up slightly at one end, rainwater will accumulate and begin to ‘pond’ on the glass. When this evaporates it can leave unsightly marks and stains behind. If you are unsure, the rooflight manufacturer should provide drawings to indicate minimum kerb heights.
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