ShedSafe Shed Specification Module 2014-15

1. SHEDSAFE SHED
SPECIFICATION MODULE
2014-15

2. INTRODUCTION
ShedSafe is an independent third party
accreditation program that covers engineering
design , documentation and building specification
for cold formed steel portal frame sheds.
ShedSafe provides Accreditation, for both
manufacturers and shed sellers.
A shed seller can only qualify if they sell sheds
supplied by an ShedSafe accredited
manufacturer as listed on the ShedSafe website
www.ShedSafe.com.au

3. INTRODUCTION
Does completing this module mean your
business is ShedSafe Accredited?
 No. Shed sellers apply for ShedSafe
Accreditation by completing the online
application form, reviewing this Specification
Module, and successfully completing the
Building Specification Questionnaire.
 ShedSafe Accreditation approval is subject to
the program Terms and Conditions, including
payment of annual fees and complying by the
program style guide.

4. DISCLAIMER
Every effor t has been made and al l reasonable care taken to ensure
the accuracy of the mater ial contained in this module. However, to
the extent permi t ted by law, the Authors, Edi tors and Publ ishers of
this Program: (a) wi l l not be held l iable or responsible in any way;
and (b) expressly disclaim any l iabi l i ty or responsibi l i ty for any loss
or damage costs or expenses incur red in connect ion wi th this
Program by any person, whether that person is the purchaser of this
Program or not . Wi thout l imi tat ion, this includes loss, damage,
costs and expenses incur red as a resul t of the negl igence of the
Authors, Edi tors or Publ ishers. Should exper t assistance be
requi red, the services of a competent professional person should be
sought .

5. SHED
SPECIFICATION
The shed seller is the best person to obtain
the intended building use, location & site
information to generate the appropriate shed
specification.
The proposed specification should be
confirmed by as correct before the building is
ordered.

6. SHEDS AND
NCC BUILDING CLASSES

7. WHAT IS THE NCC ?
 The National Construction Code (NCC) is managed by
the Australian Building Codes Board (ABCB) on
behalf of the Australian Government and State and
Territory Governments. The NCC has been given the
status of a building regulation by all States and
Territories. This means it is a regulation.
 The goal of the NCC is to enable the achievement of
nationally consistent, minimum necessary
standards of relevant, health, safety ( including
structural safety and safety from fire), amenity and
sustainability objectives efficiently.
 www.abcb.gov.au

8. SHEDS & BUILDING CLASSES
 The NCC defines buildings into 10 Building
Classes.
 Sheds generally fall into class 6,7,8,9 & 10a.
 Class 1 buildings are houses. Numerous
changes are required for a Class10a (non-habitable)
shed to comply with the NCC as a
Class 1 habitable structure.

9. GARAGES AND SMALLER SHEDS
 Class 10a sheds are generally garages and
smaller storage sheds

10. FARM SHEDS
 Where used only for storage purposes, farm sheds
are usually Class 10a. (some local authorities
classify as Class 7)

11. SHED USED FOR BUSINESS
 Where selling to the public takes place, Class 6
would apply. If wholesaling, Class 7. If used for
manufacturing, Class 8.

12. SHELTERS
 Generally people shelters are Class 9b.

13. NON-HABITABLE SHEDS
 A Class 10a shed is not required to meet the
Class 1a Housing performance criteria for a
number of factors including the serviceability &
water tightness thus a 10a shed it not compliant
as a house.

14. BUILDING
IMPORTANCE
LEVELS

15. NATIONAL CONSTRUCTION CODE
IMPORTANCE LEVELS
 The NCC assigns four different
building Importance Levels for
structures.
 The assigned Importance level is
consistent with the consequences of
building failure and the risk to human
life (or property).

16. IMPORTANCE LEVELS
 Level 1- (lowest level) Buildings or structures
presenting a low degree of hazard to life and other
property in the case of failure.
 Level 2- Buildings or structures not included in
importance levels 1, 3 or 4.
 Level 3- Buildings or structures that are designed to
contain a large number of people.
 Level 4- (highest level) Buildings or structures that are
essential to post-disaster recovery or associated
with hazardous facilities.
 Note: The Building Regulator (Certifier ) has the final
call on the Importance level.

17. IMPORTANCE LEVELS
 Farm sheds remote from other habitable
buildings are usually Level 1
 Suggested distance to other habitable
structures is 200m
 A group of farm sheds may all be level 1
 School Shelters (with more than 250
students) are required to be Level 3.

18. IMPORTANCE LEVEL 4
 The NCC Guide advises Importance Levels
must be assigned on a case by case basis
(NCC Guide Table B1.2a)
 Emergency service buildings including fire
fighting equipment sheds are generally
Importance Level 4, however a lower level may
be assigned by the builder certifier depending
on its actual use.

19. THE BUILDING IMPORTANCE LEVEL
DETERMINES THE REGIONAL WIND SPEED
 The NCC requires that regional wind speeds of
specific probability be used for building design.
ANNUAL PROBABILITY
OF EXCEEDANCE &
IMPORTANCE LEVEL
REGIONAL WIND SPEED
M/S (meters per second)
Region A Region B Region C Region D
1:100 (IL1) 41 48 - -
1:200 (IL1) - - 64 79
1:500 (IL2) 45 57 69 88
1:1000 (IL3) 46 60 74 94
1:2000 (IL4) 48 63 77 99

20. WIND SPEEDS

21. WIND DESIGN CODES FOR SHEDS
 There are currently two Wind Codes used in
Australia for design of wind actions.
 AS/NZS 1170.2 Wind Actions Code
 AS4055 Wind Loads for Housing
 Building Certifiers tend to be familiar with
AS4055 due to its use for most houses.
 A certifier cannot reject a shed designed
using AS/NZS1170.2

22. AS/NZS1170.2
 AS/NZS1170.2 is the principal Wind Actions
Code and is applicable for all classes of
buildings.
 Offers flexibility for designers and allows for
a greater range of wind speeds than
AS4055
 Is applicable to Importance Levels 1,2,3 & 4

23. AS4055 WIND LOADS FOR HOUSING
 AS4055 Wind Loads for Housing is a Wind
Code developed for housing and can only be
used for Class1 and Class10a structures.
 AS4055 has a limited scope (housing &
smaller sheds) and geometry (length, width
(16m), height & roof pitch). AS 4055 is only
applicable for structures with an Importance
Level of 2.
 Wind classifications are:
 N1 (34m/s) N2 (40m/s), N3 (50m/s) N4 (61m/s)
 C1 (50m/s) C2 (61m/s) C3 (74m/s).

24. WHY IS WIND AN ISSUE FOR SHEDS?
 Wind forces are generally the governing factor
when designing a shed, especially in medium
and high wind regions.
 It is essential to establish the site wind speed
for the intended site of the shed.
 If the site wind speed is understated, there is a
increased risk of building failure.
 If the site wind speed is over stated, the shed
may be designed to a higher specification than
is required and have more steel than is required.

25. THE RELATIONSHIP BETWEEN SITE
WIND SPEED & DESIGN PRESSURE

26. CORRECT SITE WIND SPEED IS ESSENTIAL
TO DETERMINE THE DESIGN OF THE SHED
 As the Wind speed increases, the Wind
pressure (KPA) increases at a
disproportionate rate.
(as seen on previous slide)
 When entering the details to your software
program, the input factors will determine
the site wind speed...the higher the
pressure, the stronger the shed needs to
be.

27. DIFFERENCE BETWEEN REGIONAL
WIND SPEED AND A SITE WIND SPEED
 The SITE wind speed is determined based on the
topographical factors specific to that site.
 The site wind speed is often BELOW the regional
wind speed as the terrain category classification,
and shielding (if applicable) reduce the site wind
speed.
 If the site is on a hill the topography effects would
INCREASE the site wind speed and in some
cases it may exceed the Regional Wind Speed.


28. CORRECT
SPECIFICATION
OF A SHED

29. WHAT INFORMATION NEEDS TO BE
OBTAINED FROM THE PURCHASER ?
 WIND REGION Where will the shed be built? Some sheds are
built far from where they are purchased. Will it be subject to
extreme conditions, i.e. snow, cyclones?
 USE & IMPORTANCE LEVEL What will the shed be used
for?
 TERRAIN What is the surrounding area generally like –
acreage, suburban, or rural?
 TOPOGRAPHY Will the shed be built on or near a hill, slope
or escarpment? If so this will affect the specification.
 SHIELDING Is the shed located in a Suburban area ?

30. WIND REGIONS AS PER
AS/NZS1170.2.2012
There are four wind regions in Australia- A ,B, C & D

31. TERRAIN CATEGORY –
CONSIDER TERRAIN 500M IN EVERY DIRECTION
TC1.5
Open water surfaces
subject to shoaling
waves.
Examples are near
shore ocean water,
large lakes and
unenclosed bays.

32. TERRAIN CATEGORY –
CONSIDER TERRAIN 500M IN EVERY DIRECTION
TC 2
Open terrain including
grassland with
well-scattered
obstructions having
heights generally from
1.5 m to 5 m with no
more than2
obstructions per
hectare.
Examples are open
farmland

33. TERRAIN CATEGORY –
CONSIDER TERRAIN 500M IN EVERY DIRECTION
TC 2.5
Terrain with a few
trees or isolated
obstructions, or fewer
than 10 buildings per
hectare.
Examples are
developing outer
urban areas or
acreage

34. TERRAIN CATEGORY –
CONSIDER TERRAIN 500M IN EVERY DIRECTION
TC 3
Terrain with numerous
closely spaced
obstructions having
heights generally
3m to 10m.
The minimum density
of obstructions shall
be at least equivalent
to 10 house-size
obstructions per
hectare.

35. TOPOGRAPHY
 The Topography Multiplier is a local
geographic effect. It increases the design
wind speed based on the gradient upwind of
the site.
 Google Earth is useful to evaluate topography.
WIND

36. TOPOGRAPHY (SIMPLIFIED)
 Some shed software programmes offer options
for topography including:
 Halfway up a hill
 Top of hill
This specifies a topography factor >1.0
 If the topography factor is >1.0, the suitability
of the site wind speed nominated should be
confirmed by a suitably qualified person

37. SHIELDING- SUBURBAN SITES
The Shielding Multiplier is a local development effect .
It reduces the design wind speed by taking into account
the protection afforded by upwind local buildings. A
Shielding Multiplier of 1.0 should be applied outside
suburban areas unless a lower value is justifiable.
On suburban sites where all adjoining allotments are fully
developed and the average upwind gradient is less than
0.2, a Shielding Multiplier of 0.85 may be applied as
suggested in AS/NZS 1170.2 Supplement 1.
A suburban site is defined as a fully developed area with
a number of rows of streets.

38. SHIELDING
 Structures used to provide shielding must be
the same or greater height than the shed they
are intended to provide shielding.
 Structures that provide shielding must be
located < 20h from shielded building i.e. a 4m
high shed requires shielding structures with
80m ( 4m x 20)
 Average Height of shed. The average height
as defined in AS/NZS1170.2 is the average of
the overall shed height and the eaves (gutter)
height.

39. FULL, PARTIAL & NO SHIELDING
 Full shielding would apply where there are a
two rows or more of developed structures
on all sides the shed.
 Partial Shielding would apply if there is one
row of structures on all sides.
 A shed built on a site that adjoins an open
area or parkland would have no shielding

40. SHIELDING
 For wind code AS/NZS1170.2 only permanent
buildings provide shielding, trees and
vegetation don’t provide shielding.
 You can only apply shielding IF you are
certain of the structures surrounding the
proposed site
Shielding is generally only applicable in
suburban areas

41. SPECIFICATION INFORMATION
 The following information should be
shown by all on engineering plans and
quotations:
 Importance Level
 Wind Region
 Site wind speed in m/s
 Terrain Category
 Topography factor
 Shielding factor
 Internal Pressure Co-efficient

42. EXTREME
CONDITIONS

43. EXTREME CONDITIONS
In cyclonic areas
(Regions C & D) wind
forces are much stronger.
Specific design rules
apply to claddings and
openings.
In alpine areas, sheds are
be required to resist snow
loading.

44. ALPINE AREAS
 There are 4 alpine or sub-alpine regions in Australia
 In these areas, snow build-up on roofs can lead to
structural collapse.
 Structures can be designed to resist this load, or to
shed snow to reduce loads
Classification Area Description Alpine Altitudes Sub-alpine
Altitudes
AN Northern Tablelands
(Guyra area)
NA Above 600 metres
AC Central Tablelands
(Blue Mountains)
NA Above 600 metres
AS Southern Tablelands
(Snowy Mountains)
Above 1200 metres 600 to 1200 metres
AT Tasmania
(Central Highlands)
Above 900 metres 300 to 900 metres

45. CYCLONIC AREAS
 Sheds built in the cyclonic Wind regions C and
D are subject to high wind loads and the risk
of being subjected to impact from debris
during a cyclone of storm.
 The Wind Code AS/NZS1170.2 requires sheds
built in cyclonic regions to be designed for a
“Dominant Opening", unless the whole building
envelope has test certificates to resist wind
driven debris.

46. DOMINANT OPENING
 A dominant opening occurs when part of the
structure fails, i.e. roller door, plastic roof
sheeting, cladding or is caused by impact
from flying debris.
 A dominant opening does not need to be
large, an open vent may be sufficient to
cause a build up of internal pressure.

47. ROLLER
DOORS

48. ROLLER DOORS AND
LARGE ACCESS DOORS
 Garage Door and Other Large Access Doors
standard AS/NZS4505:2012 was recently revised
and published in February 2013.
 The design wind pressures used in this standard
are consistent the two wind loading codes
AS/NZS1170.2 and AS4055, this was previously
not the case.
 This means that doors complying with the
standard can withstand the same wind rating as
the shed in which it is installed.
 AS/NZS4505:2012 is applicable to all wind
regions A, B, C & D

49. DOORS IN CYCLONIC REGIONS
 Roller and large access doors supplied in
Cyclonic regions are required by the
National Construction Code to meet the
requirements of AS4505.
 Loads on door in cyclonic regions are
significant and door mullions need to be
designed to resist these forces.

50. SHEDSAFE SHED SPECIFICATION
MODULE 2014-15
COMPLETION
 Thank you for reviewing this module.
 Please complete the Questionnaire on
the ApplyShedSafe.com.au website.
 Upon successful completion of the
questionnaire, you will receive a
Certification of Completion.