Infrastructure
Design considerations
Solid-roofed shade structures
Solid-roofed structures may have a pitched roof or a flat roof.
Design considerations
for maximum effectiveness
and useful life
Roofing material
Roof material may be aluminium or white galvanised
iron sheets to increase the rate of solar reflection. This
should last at least 25 years.
Roof height
For good machinery access, the roof height should be
at least 3.7 metres at its lowest point and at least
4.5 metres at the shed centre (for entry/exit).
Roof pitch
Lower roof pitch results in slower air movement
(e.g. 1:4 pitch or less). Steeper roof pitch results in
greater air movement (e.g. 1:3 pitch is suggested for
warmer climates).
Enclosing a shelter using sheeting, a blind or even a
furled shade cloth can contribute to significant
horizontal wind loads which can 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 to between 10 and 14° or installing it with an
inclination in excess of 20°. Roof angles of 15 to 18°
should be avoided.
Ridge opening
Provide a continuous open ridge to promote air movement
(i.e. convective heat dissipation via the ‘stack effect’).
Recommendations for open ridge space:
- 50-75 mm/3.0 m of shed width (DPC et al 2009).
- 300 mm + 50 mm per 3 m width for sheds greater
than 6 m wide for northern Australia (Davison et al
1996).
Eave overhang
The recommended overhang for open-sided sheds is
900 mm. Eave overhang is dependent on feedpad/
freestall configuration, and on eave height and degree
of protection required.
Guttering and downpipe design
As per state plumbing code (engage a qualified design
engineer).
Orientation – east-west or north-south
With an east-west orientation, and an area of 2.5 to
3 m2/cow, part of the floor area under the roof will be in
shade all day. Extending the floor about one third its
length on both the east and west to 3 to 4 m2/cow will
place feed and water troughs under shade at all times,
which will encourage intakes. More dung will be
dropped in the shaded area, which will need frequent
cleaning to avoid the risk of mastitis. East-west
orientation, therefore, works best for concrete floors.
If concrete is too costly, the north-south orientation
works best. It works well for a compacted clay or gravel
floor because the sun strikes every part of the floor area
under and on either side of the roof at some time during
the day. This helps to keep the floored area dry and
restricts pathogen build up. A shaded area of
2.5 to 3 m2/cow is adequate if feed and water troughs
are placed away from the shaded area. In regions where
temperatures average 30°C or more for up to 5 hours/
day during some period of the year, the east-west
orientation is deemed more suitable.
Shed profiles at 9 am, noon and 3 pm
at four different times of the year.
Effluent management system
An effective system for handling effluent and run-off is
essential, otherwise cow comfort, health and production
may be compromised. Refer to section 8.0 – Guidelines
for Victorian Dairy Feedpads and Freestalls (DPIV 2009).
|
Solid-roofed structures need to
comply with
regulatory authorities, e.g. a local council building
permit is required.
|
Winter and summer sunshine angles
Winter and summer sunshine angles are important, as they determine
how
much of the floor area receives sunshine
at some time during the day, given a shed’s roof height and width. Seek
professional advice.
Example:
Note the position of water trough,
grooving to help prevent cow's slipping,
water run-off from the roof to
lane, high eaves and pitched roof to facilitate
ventilation. The shed
run north-south to use sunlight to dry cow standing areas.
Note the poor drainage due to the
lack of slope. The freestall shed has
fans and sprinklers but is not
linked to good drainage -
a recipe for high mastitis levels.
Note that the sprinklers above the
feed line spray onto the cows’ backs.
The feedpad runs north-south and
has a sloping roof to reduce the
western sun projecting into the cow
resting area.
This roof slope is 18° with a 500
mm vent at the apex. Eaves are 4.3 m
high, and 6.9 m at apex. The shed
runs north-south with 3% slope on
patterned cement floor. Feed troughs
are 1.2 m wide inside, 400 mm
high and 100 mm thick.
Sprinklers could be fitted above head
lock stalls or at the back of
the cow alley in the shed.
