How deep should a shade sail post be?
As a rough trade guide, a standard 6.5 m galvanised steel shade sail post goes 1.2 to 2.2 m into the ground, leaving 5.3 to 4.3 m above ground. Small sails on sheltered sites with a large footing sit at the shallow end; exposed sites and bigger sails need the deep end. A 3.25 m half post goes 0.9 to 1.2 m deep.
This is not engineering advice. Final depth depends on sail size, wind region and soil. An engineer signs off larger jobs, schools, childcare centres and public spaces, and many councils need a permit for shade structures.
Post depth tables: in the ground vs above ground
How much post ends up above ground from standard 6.5 m pipe lengths, with an estimate of the steel cost buried in the footing vs standing above it.
Full 6.5 m post
| In ground | Above ground | Steel in ground* | Steel above* | Typical use |
|---|---|---|---|---|
| 1.2 m | 5.3 m | $55–70 | $230–310 | Small sail, sheltered site, large footing |
| 1.5 m | 5.0 m | $65–90 | $220–290 | |
| 1.8 m | 4.7 m | $80–105 | $205–275 | |
| 2.2 m | 4.3 m | $95–130 | $190–250 | Exposed site or bigger sails |
Half post (3.25 m)
| In ground | Above ground | Steel in ground* | Steel above* |
|---|---|---|---|
| 0.9 m | 2.35 m | $40–55 | $105–135 |
| 1.0 m | 2.25 m | $45–60 | $100–130 |
| 1.2 m | 2.05 m | $55–70 | $90–120 |
* Estimate only: the share of the pipe price that sits in the ground and above it, for NB100 medium-wall galvanised pipe at typical supplier prices (October 2026, GST inclusive). Prices vary by region and supplier, so check with your local steel supplier.
- A larger, wider footing (typically 450–600 mm diameter) allows a taller post above ground.
- Final depth depends on sail size, wind region and soil. An engineer signs off larger jobs.
- Pads cover the bottom of the post only: from the ground up, stopping below the lowest fixing.
Covering the bottom of the post? Pads come in 1.8, 2.0 and 2.4 m to suit the height up to your lowest fixing: see post padding sizes or order post pads.
Typical galvanised pipe prices
A 6.5 m length of medium-wall NB100 (114.3 mm) galvanised pipe typically costs $285–380 in Australia (October 2026, including GST). Most suppliers sell 6.5 m lengths, and many will cut a half length for a small cutting fee.
| Size | Wall | Per metre | Full 6.5 m length | Half 3.25 m |
|---|---|---|---|---|
| NB100 114.3 mm | Light 3.6 mm | $35–43 | $230–280 | $115–140 |
| Medium 4.5 mm | $44–58 | $285–380 | $145–190 | |
| Heavy 5.4 mm | $63–65 | $410–420 | $205–210 | |
| NB125 139.7 mm | Light 3.5 mm | $42–52 | $270–340 | $135–170 |
| Medium 4.9–5.0 mm | $59–80 | $385–520 | $195–260 | |
| Heavy 5.4 mm | about $78 | about $505 | about $255 | |
| NB150 165.1 mm | Light 3.5 mm | about $61 | about $395 | about $200 |
| Medium 4.9–5.0 mm | $71–87 | $460–565 | $230–285 |
A guide only: check with your local steel supplier. NB150: Structural 168.3 mm (e.g. 4.8 mm wall) is priced by quote. Expect a similar price per kilo to 165.1 mm medium. Pipe colour codes on the end: light yellow, medium blue, heavy red.
Concrete per footing (rough estimate)
A 450 mm hole 1.2 m deep takes about 0.19 m³ of concrete, roughly 21 bags of 20 kg premix. One bag makes roughly 0.009 m³ (about 108 bags per m³). For more than about 0.3 m³, a small pre-mixed truck load is usually easier.
| Hole depth | 300 mm dia | 450 mm dia | 600 mm dia |
|---|---|---|---|
| 0.9 m | 0.06 m³ ≈ 7 bags | 0.14 m³ ≈ 16 bags | 0.25 m³ ≈ 28 bags |
| 1.0 m | 0.07 m³ ≈ 8 bags | 0.16 m³ ≈ 18 bags | 0.28 m³ ≈ 31 bags |
| 1.2 m | 0.08 m³ ≈ 10 bags | 0.19 m³ ≈ 21 bags | 0.34 m³ ≈ 37 bags |
| 1.5 m | 0.11 m³ ≈ 12 bags | 0.24 m³ ≈ 26 bags | 0.42 m³ ≈ 46 bags |
| 1.8 m | 0.13 m³ ≈ 14 bags | 0.29 m³ ≈ 31 bags | 0.51 m³ ≈ 55 bags |
| 2.2 m | 0.16 m³ ≈ 17 bags | 0.35 m³ ≈ 38 bags | 0.62 m³ ≈ 68 bags |
Fittings and finishing
A few small details help a galvanised post last for decades.
Cap the top
Fit a galvanised post cap. An open pipe collects rain, which sits inside and slowly rusts the post from the inside out, usually at ground level where you can't see it. Caps welded on before galvanising are neatest. Push-on caps suit existing posts.
Fixing points
Weld-on padeyes or eye plates are the strongest and tidiest, best welded before the post is galvanised. Bolt-on shade sail post brackets and collars are easy to fit later and let you adjust the height. General fencing pipe clamps are fine for gates, rails and signs, but use fittings rated for shade sail loads at the sail corners.
Touch up cuts and welds
Cutting, drilling or welding after galvanising removes the zinc. Wire-brush the area and apply two coats of zinc-rich cold galvanising paint.
Let water out
A small drain hole near the base (above the concrete) lets condensation escape. Finish the concrete with a slight dome so water runs away from the post instead of pooling against it.
Sail loads, engineering and permits. Wind on a shade sail puts large forces on posts and footings. For big sails, exposed sites, schools, childcare centres and public spaces, have a structural engineer size the posts and footings. Many councils need a building permit for shade structures over a certain size. Rules vary by state and council, so check with your council before you build.
Shade sail post questions
How deep should a shade sail post be?
As a rough trade guide, a full 6.5 m galvanised steel post goes 1.2 m, 1.5 m, 1.8 m, 2.2 m into the ground, leaving 5.3 m, 5.0 m, 4.7 m, 4.3 m above ground respectively. Use the shallower end only for small sails on sheltered sites with a large footing, and the deeper end for exposed sites or bigger sails. Final depth depends on sail size, wind region and soil, and an engineer signs off larger jobs.
How deep should a half-length (3.25 m) shade sail post be?
A 3.25 m half post typically goes 0.9 m, 1 m, 1.2 m into the ground, leaving 2.35 m, 2.25 m, 2.05 m above ground respectively. Half posts suit low sails and fixing points such as playground and pergola corners.
How wide should a shade sail post footing be?
Footings for shade sail posts are typically 450–600 mm in diameter. A larger, wider footing allows a taller post above ground. An engineer specifies the footing for larger sails, exposed sites and public spaces.
What size steel post is used for shade sails?
Round galvanised steel pipe is standard: NB100 (114.3 mm outside diameter) is the most common for residential and small commercial sails, with NB125 (139.7 mm) and NB150 (165.1 mm or structural 168.3 mm) for bigger sails and taller posts. The engineer’s design decides the size and wall thickness.
How much concrete does a shade sail post footing need?
A 450 mm diameter hole 1.2 m deep holds about 0.19 m³ of concrete, roughly 21 × 20 kg bags of premix. A 600 mm hole 1.5 m deep holds about 0.42 m³ (about 46 bags), where a small pre-mixed truck load is usually easier.
Need padding for finished posts? Order post protector pads, or read about padding for childcare, schools and playgrounds.