What size shade sail do I need, and how high should it be?

Sizing depends on the area you want covered, the shape of the space, and how many fixing points are practical. As a general principle, a shade sail should be pulled taut across a shape with three, four, or more points, angled so no two sides are parallel and no two edges are the same length, since this asymmetry is what lets the fabric hold tension properly rather than sagging.

Height is a balance: too low and the sail feels oppressive and blocks airflow; too high and it loses effectiveness at blocking low-angle morning and afternoon sun. A workable starting point for most patios is around 2.4 to 3 metres at the low corner, rising higher at the opposite corners for drainage fall, though the right numbers depend on your specific structure and fixing points. This is exactly the kind of detail that benefits from a site visit rather than guesswork, which is why WeatherSafe WA’s free measure and quote includes working out sizing and height on site.