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Design and Project Services for Shade Sails

Design Shade Sails that work, look good and provide value for money.

Shade Sail Design Guidelines for structures that work, look good and provide long-lasting shade.

Design guidelines are a crucial part of the implementation of Shade Structures, to ensure maximum serviceability.

Shade Sails design guidelines
The purpose of this page is to provide the ‘layman’ of Shade Sail design with in-depth Shade Sails guidelines and knowledge. This is so that anyone can design shade sails that work, look good and provide value for money.

It is typically aimed at schools, councils, builders and architects, who want to install small-to-medium Shade Sails for government and private projects. It doesn’t cover in detail any highly specialised structures (like large tensile membrane structures, car park structures or membrane facades).

Shade Sails are a great way of covering large areas in an attractive, functional and economical manner. When designed and built properly, Shade Sails are a permanent solution. There are several frequently raised questions, and it would be best to address these first:

Q Are shade sails temporary structures?

A No. While a Shade Sail can be removed if required, the structures are typically designed to be a permanent fixture and are engineered to withstand the same wind and storms as the surrounding buildings. A properly designed and certified structure that is correctly maintained will not ‘blow away’ or ‘fall down’ in any normal storm. Life expectancy on a Shade Structure is typically 15+ years.

Q Do you have many problems with vandals?

A No. Structures are designed to be vandal resistant. While a determined vandal can damage almost anything, the intent is to make the structures too difficult to vandalise, so the vandals go elsewhere. This is achieved with minimum height clearances and anti-vandal climbing devices on columns, fire retardant shade cloth and smart column location.

Design standards
Unfortunately there are very few national and international standards which directly apply to Shade Sail design guidelines. There are a number of Australian Standards and also sections of the National Construction Code (NCC) which apply to projects, and Greenline advises that a professional, i.e. building certifier or architect, be involved, to identify and ensure compliance with all standards and codes. Some of the common standards and codes are:

Shade specific and general construction

• AS 1170 – structural design actions

• AS 3600 – concrete structures

• AS 3610 – formwork for concrete

• AS 1671 – steel reinforcing materials

• AS 1554 – structural steel welding

• AS 1627 – metal finishing

• AS 4100 – steel structures

• AS 4174 – synthetic shadecloth

• AS 2001 – methods of test for textiles

• AS 1530 – methods of fire tests on building materials, components and structures

Carpark

• AS 2890 – facilities

Lighting

• AS 3000 – electrical installations

Playgrounds & parks

• AS 4685 – playground equipment

• AS 4486 – playgrounds & playground equipment

Key design criteria for Shade Sails
There are a number of key design criteria to consider when specifying or building a Shade Sail structure:

• Engineering

• Steelwork selection and heights

• Steelwork detailing

• Coverage of area

• Size of sails

• Heights of sails

“When designing structures, try to keep the length of the sail to not more than 70% larger than the width.

Area usage

Key items to define are the purposes of the structure:

• What area is to be covered?

• What times of the day/year to be covered/not covered? Sometimes it can be uneconomical to cover a full playground for all          daylight hours (eg. 8am to 4pm) as the shadow from the Shade Sails moves drastically across the ground throughout the day,      and covering a 100m² area might require a shade 3 or 4 times that size to provide continuous shade. Consideration should          also be given to adjoining buildings/trees which can provide shade in the area. Overshadowing of adjoining properties/areas      should also be considered.

Shade Sails column location
Shade Sail designs should consider column location. Shade Sails do not have to have a regular or symmetrical plan area, but there are certain limits as to how irregular a structure could be. When designing structures, try to keep the length of the sail to not more than 70% larger than the width. Keep the larger diagonals to within 200% of the shorter diagonals. Typical minimum/maximum spans are as follows:

Material                                                              Minimum                                  Maximum

Light/residential duty shadecloth (>320gsm)         4m                              7m Medium shadecloth (320 – 370gsm)                                                                                                                             6m                              14m Heavy shadecloth (370 – 400gsm)                                                                                                                             8m                              20m

When placing columns, consider usage of the area and surrounding structures & buildings – key items to consider:

• Fall zones of playground equipment

• Pedestrian flow

• Services, i.e.: sewer, power, water, data below ground, and power lines above the ground (contact DBYD 1100)

• Proximity to retaining walls, trenches etc.

Shade Sail heights
Shade Sails require minimum ‘height difference’ or ‘fall’ across the sail, to maintain tension and look good. Typically, a four post Shade Sail has two high and two low points, diametrically opposed to create a ‘saddle’ or ‘Hypar’ (hyperbolic paraboloid) shape. A ‘Skillion’ shape can work, but exerts greater forces onto the columns and does not maintain tension as well. A typical guide for minimum height difference is: Minimum height difference (m) = longest diagonal (m) ÷ 7
Shade Sail heights
Also, as part of critical design guidelines, attention should be paid to the height of the infrastructure below ,and adjoining, the proposed Shade Sail. Special consideration should be given to playground equipment and climbing equipment, to ensure that the sail remains out of reach of the users. There are no standards for clearance above the structure (except the NCC, which states that all structures should provide greater than 2100mm head height) but Greenline design guidelines recommends the following minimum clearances:
Steelwork selection
Selection of the right type of columns is critical to the final appearance and longevity of the structure. CHS columns are the most common and work the best.
Column detail
It is important that columns have welded caps and lugs, to prevent moisture entering the column and rusting it out.
Columns
Columns are typically installed on a lean (or rake). The reason for this is for both aesthetics and functionality. Shade Structures are designed using high deflection analysis software. Columns are designed to deflect (bend) within a given allowance, as per structural designs. This means that columns installed ‘plumb’ have the capacity to deflect inwards, giving the appearance of ‘falling over’. While this is not the case, deflection is not noticeable when columns are installed with a slight lean.
Footing detail
Shade Sails typically have wet-set foundations. If baseplated designs are used, ensure that the baseplate and hold-down bolts are concealed well below the finished ground level (generally 150mm below). See also ‘footing types’ for more info.
Column lean
Columns typically are installed with between 2.5° and 5° of lean. Columns are leaned away from the direction of pull, which is typically the approximate centre of the sail.
Column protective coatings
There are three main types of protective coating used on Shade Structure steelwork:

1. Powdercoat

2. Hot dip galvanising

3. Two-pack paint

Footing types
A bored pier is the most common method for construction of Shade Structure foundations in eastern Australia. A bored pier footing relies on the lateral strength of the soil to counter the moment forces applied onto it. Bored piers can be impractical in sandy soil (low cohesion of the soil makes the sides of the footing ‘cave in’) or rocky sites (too hard to dig). These sites can call for pad-style footings, which typically require significantly more concrete than piers.
Geotechnical Report
A geotechnical report can be conducted to determine the soil type and best footing type. Other items to pay attention to are the water table (a high water table can cause problems with excavation) or highly reactive soils (soils that move a lot with changes in moisture level).
Shade Sail attachment points
Shade Sail attachment points
Shade Cloth detailing
Shade Sails should be manufactured from a commercial grade shadecloth. There are a number of good brands available; Greenline recommends the following:

Parasol Protex – excellent shade mesh for small to medium structures (up to 200m² per cover); available in 10 fire retardant colours. UVR block of between 88.7% and 94.4%. Nominal 325gsm. 10 year UV warranty.

Architec 400 – excellent shade mesh for medium to large structures, available in 11 colours. UVR block of between 87.7% and 96.0%. Nominal 400gsm. 12 year UV warranty.

UVR block requirements: The only standard calling for minimum UVR block applies to childcare centres and it calls for minimum 94% UVR block. The small difference in UVR block between colours doesn’t make any difference to performance and is not noticeable to users of the area. Most shadecloths are tested un-tensioned anyway, and will open up slightly once installed.

Fire Retardant: Most shadecloths have some degree of fire retardancy. The test is conducted under AS 1530 part 2 and part 3. The actual standard does not have a ‘pass’ or a ‘fail’ but just is a recognised method of determining the fire retardancy level of a particular shadecloth.

Note: ‘Fire Retardant’ shadecloth means that the cloth shouldn’t burn without a heat source. The cloth will still melt when a flame is applied, but shouldn’t continue to burn once the flame is withdrawn. Obviously if you have a bush fire going through the area, the sail is still going to burn down!

NOTE:

Information in this publication is subject to copyright and is intended as a guide only. Greenline cannot take any responsibility for any loss or damage arising out of use of the information supplied herein.

UV stabilised PTFE thread.
It is important that sails are sewn with UV stabilised PTFE thread. ‘Standard’ cotton threads are not UV stabilised and can deteriorate quickly. Sails need to be designed and manufactured to take the loads applied onto them, including specialised seams and ‘doublers’ or double-thickness fabric reinforcing.
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