The right size and slope for a shade sail
Measuring up for a shade sail looks simple, and it is, as long as you get three things right: leave enough tensioning space, position the fixing points correctly and give the sail enough slope.
Do that and your sail hangs taut, the water runs off and the fabric cuts through the wind instead of flapping. In this guide you'll find how much space a standard size needs, how to measure up for a made-to-measure sail and which slope to aim for.
Tell us about your situationWhat you'll find below
Start with the question of whether you're working with a standard size or a made-to-measure sail. The rest of the guide follows from there.
A shade sail in a standard size
Looking for a sail in a standard size? Then you need enough free space to install the sail and bring it up to the right tension. You can also work the other way around: start from the space you have and check which standard size fits into it.
With a standard size the dimensions of the sail are fixed. So you adjust the fixing points to the sail, not the other way around.
How much free space do you need?
Between every corner of the sail and its fixing point, allow for:
The distance may differ from corner to corner, as long as you stay within those limits everywhere.
You need that minimum of 35 cm to be able to tension the sail properly. Place the fixing point more than 100 cm from the corner and the tensioning run becomes too long: in strong wind the sail can move and flap more, with a greater risk of damage to the fabric or the fixings.
A sail of 400 x 400 cm
A shade sail of 400 x 400 cm needs a space of at least 470 x 470 cm and at most 550 x 550 cm:
In the drawing the sail hangs 35 cm from the poles on the left-hand side and 100 cm on the right-hand side. The distances between the fixing points then become:
Anchoring with poles at 90° or 80°
Working with existing poles? Then your fixing points are already set. In that case, check whether they sit at the right distance to tension your chosen sail properly.
Installing new poles? Then the right position depends on the angle: upright at 90° or leaning outwards at 80°. That applies to aluminium and wooden poles alike, and to standard sizes as much as to made-to-measure sails.
Pole at 90°
An aluminium or wooden pole installed upright at 90° stands at least 35 cm and at most 100 cm from the corner of the sail. You need that space to tension the sail properly.
Ignore that distance and either the sail won't come up taut enough, or the tensioning run becomes so long that the sail starts to move in the wind.
Pole at 80°
An aluminium or wooden pole leaning outwards at 80° can have its foot closer to the dimensions of the sail. The lean creates roughly 35 cm of extra distance at the fixing point.
That means the foot of the pole can sit level with the corner of the sail, or up to 75 cm further out.
A made-to-measure shade sail
Our standard sizes fit plenty of situations, but not every one. With a made-to-measure shade sail we match the shape and the dimensions to the fixing points you have. Ideal for an irregular layout, or whenever you want the sail to follow your space as closely as possible.
Wherever we can, we design the sail as close to the fixing points as possible, with a minimum distance of 35 cm between the sail and each point. Only where there's no other option do we adjust the length of the tensioning run to bridge larger distances. The difference with a standard size: there you move the points, here the sail moves with you.
A–B 547 cm | B–C 565 cm | C–D 510 cm | D–A 478 cm
Differences in height help determine the slope and the final shape of the sail.
A 300 cm | B 225 cm | C 290 cm | D 235 cm
A–C and B–D serve as a check: if they don't match your other measurements, there's a measuring error somewhere.
No suitable measuring tool? Request a tape measure below.
Check your measurements
Enter the distances between your fixing points (in cm). The calculator checks whether your measurements add up to a valid shape, works out the diagonal and the area, and compares them with your own check measurement.
Our sails go up to 700 cm per side for a triangle and 800 cm for a quadrilateral, with a maximum area of 49 m². Above that, or below 250 cm? There's still a solution, but it's best we look at it together.
Getting the slope right
A shade sail gives you pleasant shade, but it also has to cope with rain and wind. That's where the slope comes in: with the right angle the water runs off, the wind load drops and the sail stays taut.
Below you'll find the options, from a flat installation to the two ways of sloping a four-cornered sail.
A flat shade sail
Installing a sail flat is possible, but only in ideal conditions: sunny days, little or no wind and no chance of rain. It looks sleek and modern, but without a slope rainwater has nowhere to go. That leads to pooling water and needless strain on the sail and the fixing points.
We therefore only recommend a flat installation for temporary set-ups or in a dry climate. If you want your sail to last and keep performing, a sloped installation is always the better choice.
The risk of pooling water
With a flat installation, rain quickly starts to pool. Even breathable fabrics don't let water through fast enough, and waterproof fabrics don't let anything through at all.
That creates pockets of water which put excessive strain on the sail and can tear it. A pocket just a few centimetres deep already weighs tens of kilos. That's something to avoid at all times.
The right slope
A shade sail is best installed with a slope of 25 cm per running metre, measured from the highest to the lowest point.
So a 4 x 4 m sail is best hung with two high fixing points at 3 m and two low ones at 2 m — that's a drop of 4 × 25 cm. This gives you good water run-off and optimal tension in the sail.
Work those heights out before you choose your poles. A 6 x 6 m sail needs 150 cm of height difference: with 3-metre poles your lowest point would sit at just 150 cm. In that case you're better off with 4-metre poles.
Different slope configurations
With a triangular sail it's straightforward: you drop one corner and the slope is there.
With a four-cornered sail you have two options. You lower two fixing points along the same side, or you lower two opposite corners. With that second option you spread the height difference over both points, so you don't have to drop as far.
- Two low points along the same side | for 4 x 4 m: two points at 300 cm, two at 200 cm
- Two low points diagonally opposite each other | for 4 x 4 m: two points at 300 cm, two at 250 cm
Water and wind
When positioning your sail, take external factors such as wind and rain into account. The prevailing wind direction matters most.
Ideally, place the lowest point or points in the direction the wind blows, not against it. That reduces the wind pressure on the sail and stops rain being blown underneath it.
Make sure the sail is always properly tensioned as well. A poorly tensioned sail flaps in strong wind and passes the shock loads on to the fixings, which can tear the fabric or work the anchor points loose. The tauter the sail, the better it cuts through the wind and the longer it lasts.
Frequently asked questions about size and slope
How much space do you leave between the poles and the sail, how much slope do you need, and what if your space isn't perfectly square? The answers to the questions we get most often about measuring up for a shade sail.
Allow at least 35 cm and at most 100 cm per corner between the sail and the fixing point. So for a sail of 400 x 400 cm you need a space of at least 470 x 470 cm and at most 600 x 600 cm. That space isn't a margin, it's the room you need to tension the sail properly.
An upright pole (90°) goes 35 to 100 cm from the corner of the sail. A pole leaning outwards (80°) gains roughly 35 cm at the fixing point, so its foot can sit level with the corner of the sail, or up to 75 cm further out.
How do you work out the right size for your shade sail?
The size of a shade sail is not the size of the space you want to cover. Between every corner of the sail and its fixing point you need room to tension the sail: at least 35 cm and at most 100 cm. So a sail of 400 x 400 cm calls for a space of at least 470 x 470 cm and no more than 600 x 600 cm.
That tensioning space isn't a margin you can leave out. Hang the sail too close to the pole and you'll never get it taut; leave too much room and the tensioning run becomes so long that the sail starts moving in the wind. So always measure the space you have first, and only then choose your size.
Where do you position the poles for your shade sail?
The position of your poles depends on the angle you install them at. An upright pole (90°) goes 35 to 100 cm from the corner of the sail. A pole leaning outwards (80°) gains roughly 35 cm at the fixing point: its foot can then sit level with the corner of the sail, or up to 75 cm further out.
Working with an existing facade, a wall plate or a ground fixing instead of poles? The same rule applies: the fixing point sits 35 to 100 cm from the corner of the sail.
How much slope does a shade sail need?
Never hang a shade sail flat. Allow 25 cm of slope per running metre, measured from the highest to the lowest point. For a sail of 4 x 4 m that means two fixing points at 3 m and two at 2 m.
Without a slope, water sits in the lowest fold during a heavy shower. A pocket like that quickly weighs tens of kilos, pulls the sail out of shape and strains the fixing points. With a waterproof sail the slope is the only thing carrying the water away; with a breathable sail most of the water runs through the fabric, but you still need slope for the tension and for the last of the water.
Having a shade sail made to measure
If your space isn't square or rectangular, we'll make the sail to measure. In our own production facility in Belgium we cut and sew every made-to-measure sail to the dimensions you send us.
What we need from you:
Use a tape measure or a laser distance meter if you can. Not sure about your measurements, or about the size you need? Get in touch through the form below we'll go through the figures with you.
A direct answer
Have your measurements checked
Send us your dimensions, a sketch or a few photos of your fixing points. We'll check the sizing, the tensioning space and the slope before you order. No suitable measuring tool at hand? Request a tape measure here and we'll look at how to help you further.
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