SHEDSAFE SHED

SPECIFICATION MODULE

2014-15

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

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.

INTRODUCTION

Every effort has been made and all reasonable care taken to ensure

the accuracy of the material contained in this module. However, to

the extent permitted by law, the Authors, Editors and Publishers of

this Program: (a) wil l not be held l iable or responsible in any way;

and (b) expressly disclaim any l iabil i ty or responsibil i ty for any loss

or damage costs or expenses incurred in connection with this

Program by any person, whether that person is the purchaser of this

Program or not. Without l imitat ion, this includes loss, damage,

costs and expenses incurred as a result of the negligence of the

Authors, Editors or Publishers. Should expert assistance be

required, the services of a competent professional person should be

sought.

DISCLAIMER

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.

SHEDS AND

NCC BUILDING CLASSES

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

WHAT IS THE NCC ?

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 .

SHEDS & BUILDING CLASSES

GARAGES AND SMALLER SHEDS

Class 10a sheds are generally garages and

smaller storage sheds

Where used only for storage purposes, farm sheds

are usually Class 10a. (some local authorities

classify as Class 7)

FARM SHEDS

Where selling to the public takes place, Class 6

would apply. If wholesaling, Class 7. If used for

manufacturing, Class 8.

SHED USED FOR BUSINESS

Generally people shelters are Class 9b.

SHELTERS

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.

BUILDING

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).

NATIONAL CONSTRUCTION CODE

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.

IMPORTANCE LEVELS

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.

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.

IMPORTANCE LEVEL 4

The NCC requires that regional wind speeds of

specific probability be used for building design.

THE BUILDING IMPORTANCE LEVEL

DETERMINES THE REGIONAL WIND SPEED

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

WIND SPEEDS

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

WIND DESIGN CODES FOR SHEDS

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

AS/NZS1170.2

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).

AS4055 WIND LOADS FOR HOUSING

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.

WHY IS WIND AN ISSUE FOR SHEDS?

THE RELATIONSHIP BETWEEN SITE

WIND SPEED & DESIGN PRESSURE

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.

CORRECT SITE WIND SPEED IS ESSENTIAL

TO DETERMINE THE DESIGN OF THE SHED

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.

DIFFERENCE BETWEEN REGIONAL

WIND SPEED AND A SITE WIND SPEED

CORRECT

SPECIFICATION

OF A SHED

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 l ike –

acreage, suburban, or rural?

TOPOGRAPHY Will the shed be built on or near a hil l, slope

or escarpment? If so this will affect the specification.

SHIELDING Is the shed located in a Suburban area ?

WHAT INFORMATION NEEDS TO BE

OBTAINED FROM THE PURCHASER ?

There are four wind regions in Australia- A ,B, C & D

WIND REGIONS AS PER

AS/NZS1170.2.2012

TC1.5

Open water surfaces

subject to shoaling

waves.

Examples are near

shore ocean water,

large lakes and

unenclosed bays.

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

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

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.

TERRAIN CATEGORY –CONSIDER TERRAIN 500M IN EVERY DIRECTION

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.

TOPOGRAPHY

WIND

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

TOPOGRAPHY (SIMPLIFIED)

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.

SHIELDING- SUBURBAN SITES

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.

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

FULL, PARTIAL & NO 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

SHIELDING

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

SPECIFICATION INFORMATION

EXTREME

CONDITIONS

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.

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

ALPINE AREAS

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

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.

CYCLONIC AREAS

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.

DOMINANT OPENING

ROLLER

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

ROLLER DOORS AND

LARGE ACCESS DOORS

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.

DOORS IN CYCLONIC REGIONS

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.

SHEDSAFE SHED SPECIFICATION

MODULE 2014-15