The most common shade sail mistake isn't the colour or the shape. It's the size. A sail that is too big can't be tensioned, and a sail that is too small leaves you with long gaps and a lot less shade than you expected. The good news: getting it right takes five minutes, a tape measure and a second pair of hands.
1. Find your fixing points first
Before you measure anything, decide where each corner will attach. A shade sail pulls hard on every corner, especially in wind, so each fixing point needs to be solid: a masonry wall, a structural beam, a steel or timber post set in concrete, or a large, healthy tree. Gutters, fascia boards and thin cladding are not fixing points.
A triangle needs three points. A square or rectangle needs four. If you only have two solid points, you'll need posts for the others, and if you're not sure a wall or beam is strong enough, ask a qualified tradesperson.
2. Measure between the fixing points
- Measure the straight-line distance between each pair of neighbouring fixing points, at the height the corners will sit.
- On a four-point layout, also measure both diagonals. If the two diagonals are very different, your points don't form a true rectangle, and that's worth knowing before you order.
- Write every measurement down with a quick sketch. You'll thank yourself later.
3. Leave room for the fittings
This is where most people go wrong: the sail must be smaller than the space between your fixing points. You need room for the carabiners and turnbuckles that tension each corner. As a guide, allow 15–30 cm between each corner of the sail and its fixing point.
Example: if your fixing points are around 4 m apart, look at a sail of around 3.6 m on that side.
4. Remember the curved edges
Most shade sails have slightly curved edges so they can be tensioned flat and tight. That means the shade on the ground is a little smaller than the listed size of the sail. If you need to cover a specific table or play area, go for the size that gives you a margin.
5. Plan the heights
Corners at different heights look better and work better. On a square or rectangle sail, put two high corners on one diagonal and two low corners on the other: the twist keeps the fabric tight and lets rain run off. On a triangle, fix one corner lower than the other two. Our installation guide covers slope and tension in detail.
6. Think about where the sun comes from
In Australia, the midday sun sits in the north and the hottest afternoon sun comes from the west. If you mostly use your outdoor area in the afternoon, position the sail on the west side of it. The shadow moves through the day, so measure for the time you'll actually be outside.
Not sure about your numbers?
Send us a photo of your space and your measurements through our free Size Check. We'll reply by email with the size we recommend and a total price including delivery.
This article is general information, not engineering advice for your site. Check with your local council whether your installation needs approval.