Shade cloth structures
Several forms of shade cloth structures are available
including span structures (such as the case study on
page 20), peaked sail structures, cantilever structures
as pictured below and tent like structures with large
for maximum effectiveness
and useful life
For dairy cattle, use shade cloth which blocks at least
80% of sunlight, with a minimum 300 gsm (grams per
square metre). Green or black coloured material is
preferred. Shade cloth fabric should last at least 10
years. Higher quality and tighter weave fabrics last
longer but cost more.
Shade cloth fabric can deteriorate relatively quickly with
exposure to sunlight, dust, accumulated debris and
water. Flexing will encourage deterioration and wear as
well as failure or loosening of connections. Shade cloth
is also prone to bird, insect and rodent attack and areas
not able to be hosed down or easily inspected for
maintenance are particularly prone.
Note: Cows are also not keen on going from bright
areas to dark areas and prefer dappled shaded
spaces to dark spaces, so they tend to get used to a
shade cloth structure more quickly than a solidroofed
structure, provided the cloth is not billowing
or flapping noisily.
Fastening fabric to posts
Shade cloth must have sufficient tension applied to it to
prevent the cloth from damage during windy conditions.
The flexible and adjustable connections between the
fabric and the support posts are therefore critical
The shade cloth fabric can be held to posts in different
ways, ranging from load-carrying straps to chains and
u-bolts and in the most advanced form adjustable
cables and turnbuckles.
How long the connection lasts usually depends on how
well it distributes the point load at the stanchion to the
fabric. Reinforcing cables and seams help.
If excessive flexing of fabric is permitted the flapping
can generate unacceptable noise during wind events
which can disturb cows and irritate people. However,
compared to metal frames and buildings, shade cloth
structures suffer minimal temperature or water related
If a cable or cable connector fails due to overtensioning,
it can cause instantaneous and catastrophic
Turnbuckles for tensioning cable supported shade cloth
structures are prone to loosening or failure through
repetitive loading so they should be inspected regularly
and tightened or replaced.
Chain connections should be avoided. In the event of
overstress, breakage of a link can lead to the launch of
a projectile whereas a cable will fray or unravel, allowing
time for repair, replacement or escape from injury.
Shade cloth structures can become a hazard if
damaged by storms. Blown cladding can provide
serious injuries whilst broken cables and unsecured
shade cloth can whip.
Different fastening methods.
Support posts and foundations
Ensure structural grade steel is used. For rigid framed
and flexible shade cloth structures the wind loads, dead
loads and live loads imposed on the structure need to
be transferred through the structure into the ground.
The foundations which secure each post to the ground
are therefore critical structural components.
Deep, concreted footings are essential as the posts are
subject to a ‘bending moment’ and need to transfer
stresses into the ground, as well as to stop the structure
lifting. Each post should be rigidly attached to a wide
steel plate which is mounted on the foundation using
bolted connections. Galvanised and threaded starter
bars extending from the footing reinforcement are better
for holding the plate than dynabolts.
Apart from central supports these posts usually lean
against the applied horizontal load to maintain the
tension rather than being vertically upright. They need to
be free standing in a farm situation. Guy cables must be
Deep footings should be left to cure for an extended
period before bearing any load.
Avoid collisions between animals and vehicles with
posts, cables and cladding. If possible, position posts
outside the animal traffic area so they are not in contact
with manure and water or interfere with washing (If are
located in the yard, place a raised concrete or PVC
sleeve around the pipe to reduce corrosion potential).
If the shade cloth is suspended too high, it will limit the
area of shaded footprint.
A minimum height of 4.0 m is recommended to ensure:
cows do not interfere with it and are happy to walk
under it (Low shade cloth structures can put cows
off entering an area)
effective installation and use of sprinklers and fans
machinery can readily traffic the area without risk of
tearing it or burning holes in it with their exhaust pipe
adequate airflow underneath the structure.
The height of the structure, the angle of winter and
summer sun and the required area of shaded footprint
govern the orientation of the shade structure – northsouth
or east-west. If the structure is aligned east west
the passage of the sun will generally ensure that the
northern side of the structure is more exposed to
sunlight than the southern.
Drainage from shade cloth must be considered,
particularly if the paving is earth. Ideally, any drainage
should be directed to formed drains rather than earth
that is subject to animal traffic.
WEAKNESSES IN shade
usually associated with:
- cyclic loading conditions
- lack of fabric strength
- inadequate fabric reinforcement at connections
- connections to stanchions which are prone to fatigue
- failure of footing connections, leading to loose posts
- spans which can lead to billowing
- corrosion of metal
- degradation of fabric
- rain, hail or debris accumulating on top of the
Stresses on shade cloth
A shade cloth structure must be strong enough to
withstand three types of load: ‘wind load’, ‘dead load’
and ‘live load’.
Wind load is usually the largest load carried by a
light-framed agricultural or industrial building taking the
form of a tensioned shade cloth or a rigidly clad framed
Wind loads impose unbalanced forces on a shade
cloth, generating ripples or waves that may lead to
premature failure of fabric or other components. This
problem can be alleviated by ensuring that the shade
cloth is adequately tensioned.
Horizontal wind loads can also contribute to structural
failure. If the angle of inclination of a roof or shade cloth
is 15° or so, it will generate lift (The roof behaves like the
leading edge of an aircraft wing). Lift can be minimised
by either flattening the inclination of the roof or shade
cloth to between 10 and 14° or installing it with an
inclination in excess of 20°. Roof angles of 15 to 18°
should be avoided.
Sailcloth structures are particularly prone to ripping in
response to high wind loads, inadequate fabric
strength, lack of structural reinforcement and excessive
spans which can lead to billowing.
Dead load refers to the weight of the structure
(downward force due to gravity) which must be
withstood by the posts. Bracing in frames or cables
supporting shade cloth are usually employed to ‘stay’ or
Posts supporting shade cloth are frequently installed at
an angle to help provide tension but this can also
contribute to instability when the cable support is
While the dead load of a metal clad framed structure is
high by comparison with a shade cloth structure, the
load imposed by shade cloth should not be
underestimated, particularly if the loading is not well
distributed. Cloth impregnated with dust or supporting
leaves, twigs, hail, ponded water or wetted from
beneath by sprinklers can also be quite heavy and the
cables and connections which form the structural
system are not light.
Live load refers to brief, temporary loads such as those
associated with someone on a roof, hailstones or rainfall
cascading down a roof, water pooling on the canopy or
being shed through or from shade cloth.
If metal clad frameworks and shade cloth structures are
not designed to carry human traffic it is not surprising
that failure occurs when they do. Safe OH and S
practice must restrict access to these structures.
While shade cloth is designed to pass some light and
air as well as water it is not unusual for some of the
gaps in the mesh to be clogged. If the mesh gets
clogged and water pools, an excessive live load is
possible which can lead to fabric failure at best or
structural failure at worst.
If you intend to install a shade
structure, consult a
registered builder or structural engineer who
understands how to design and build a structure which
will withstand these loads. Alternatively , if you are
buying a package shade cloth structure ensure that
structural computations are supplied, the installers are
experienced and local building regulations are met.
ADVANTAGES OF a shade
over a solid-roofed shade structure:
- Lower cost (less than half that of a solid-roofed
structure covering the same area).
- You have the option of removing the shade cloth
in the cooler months of the year. (Ensure that you
store the fabric to protect it from vermin.)
- If fabric degrades or is damaged it can be easily
replaced with better material and the connections
upgraded to better reflect farm needs.
- If severe storms are forecast, the fabric can be
furled or removed to limit damage.
- If well designed, installed and maintained there is
no greater risk of failure of these structures
compared with other farm buildings.
- Different types of fabric offer different degrees of
- Technological developments are rapidly leading to
better fabrics and connections and longer lasting
- If well made, the posts and foundations are long
- It is possible to extend shade cloth structures
without the same attention to drainage that a
solid-roofed structure requires.