Shed Talk

Here we talk about the technical side of the shed and the slang used in the industry. Our aim is to provide information to assist you in buying your new building. If you have any question please don’t hesitate to call us, and one of our authorised agents will be happy to assist you.

Site Specific Engineering

Many shed suppliers will supply you with generic engineering which covers all areas with no consideration to terrain and shielding of the building. Site specific engineering ensures the building is designed for your area and location giving you peace of mind and assurance that the building you purchase is fit for purpose. Many local authorities around Australia will not accept engineering unless it is site specific.

Wind speed

Wind speed may be referred to in many ways. W33 , W41, W50, W50C or N1, N2, N3 and N4 are all superceded methods of stating winds speed. Anyone quoting these wind speeds are not keeping up with current engineering requirements as set out by the Building Code of Australia (BCA).

Wind speed is measured in metres per second (m/s), N40 – N50 – N60 are the new wind codes all building should be designed to (example N40 = wind speed of 40 metres per second m/s).

How is strength determined?

Strength of the building can be determined many ways. The rule of thumb used in the shed industry is the weight of the building. When getting quotes always ask what the weight of the building is, the kit that weighs more for the same size building will indicate it has heavier steel components than the kit that is lower in weight. Generally, the kit that is heavier in weight will be stronger and may cost more.

What is the gable end?

The gable is the end of the building which shows the roof pitch and highest point of the structure. The gable end can also be called the end wall. 

What is the span?

Span refers to the gable/skillion end of the shed and indicates the width of the building.

What is roof pitch?

Roof pitch is the angle the roof falls from the ridge to gutter. The available roof pitch options include: 

  • Gable Sheds: 10°, 15°, 20°, 25°, 30°
  • Skillion Sheds: 6°, 12°
  • Gable Carports: 10°, 15°, 20°, 25°
  • Skillion Carports: 6°

What is the apex?

Apex refers to the top of the roof and is also known as the ridge.

What is a rafter?

Rafter refers to the beam that follows the pitch of the roof from the apex to the gutter. Rafters are a major structural component that supports the roof.

What is a column?

Column refers to the section that fixes to the floor with a bracket and bolts to the rafter with a bracket. Columns are major structural component that supports the roof and walls.

What is the knee joint?

The knee joint is the point where the column and rafter are joined by the knee bracket or knee plate. 

What is the apex joint?

The apex joint is the point where the left and right rafter are joined by the apex plate. The further the bracket wraps around the rafters, the stronger the joint is.

What is a portal frame?

Portal frame refers to both columns and rafters bolted together using knee plates and an apex plate. Multiple portal frames can be joined to create a shed or building. 

What does building length mean?

Length of the building is determined by the distance from one gable end to the other gable end. It is determined by the number of bays multiplied by the width of the bays. As an example, you may have a 9 metre long building made up of 3 bays at 3 metres each.  

What is a bay?

Bay of the building is determined by the distance from one portal to the next portal. Number of bays multiplied by the bay widths determines the length of the building. 

What is the building height?

Height of the building is from bottom of column to the top of the eave purlin along the length of the building. In a skillion roof building there will be a high side and a low side when discussing height. 

What is barn height?

Barn height is determined by two heights, outer wall and inner wall. The inner wall is the main body/tower of the barn whereas the outer walls are the enclosed awnings of the barn.

Does the roof pitch change on a barn?

The roof pitches on a barn can be the same or you can also have a higher roof pitch on the main body of the barn and a lesser pitch on the awnings. We even offer skillion roof barns. 

What is clear span?

Clear span is the distance from column to column without any internal post supporting the roof.

How far can I span?

With our pre-engineering we can span from 3 metres to 30 metres. The maximum span possible on your site will be determined based on your specific design criteria.

What is a purlin?

In the shed industry purlins refer to the steel roof battens that span across your portals to support the roof sheets. The more purlins you have, the stronger the building becomes.

What is an eave purlin?

The eave purlins run the length of the building and provides a fixing point for the wall and roof sheeting.

What is a girt?

In the shed industry girts refer to the steel wall battens that span across the portals to support the wall sheets. The more wall girts, the stronger the building.

What is a mullion?

Mullions are support columns for the gable end (end walls) and roller doors. Referred to as front wall mullions, back wall mullions and roller door mullions, wall girts can only span a certain distance. The engineer inserts a mullion to share the load of the wall it is supporting in the gable ends.

What is a header?

The header refers to a beam running across an opening of a window, door or roller door. It is used to attach sheeting and give additional strength to the opening.

Do I need bracing?

Bracing is very important to the structure of your building and is determined by wind loading, terrain and location of the building. The amount of bracing required will be determined by Steel Buildings Australia and the Engineer.

What is TCT?

TCT stands for Total Coated Thickness and is the thickness of the base metal after it is coated with colour. TCT sizes in the shed industry are as follows .42TCT - .47TCT - .53TCT. Any other size may indicate imported steel.

What is BMT?

BMT stands for Base Metal Thickness and is the thickness of the material before it is coated. BlueScope BMT sizes in the shed industry are as follows: .35BMT, .42BMT, .48BMT. Any other size may indicate imported steel.

What are flashings?

Flashings are used to cover sheeting were it meets at a corner. Flashings will weatherproof the building. Some companies don’t use corner flashings, they expect you to bend high tensile sheeting around the corner of the building. 

What is a C or Z section?

C/Z Sections are used extensively in the shed industry to make the main frame of the building and mezzanine floors. The span (width) of the building and wind loading will determine the size of C/Z section used.

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