A glossary of terms frequently encountered in this document section is to further help you describe the building you want to design or understand what you are purchasing. Pass comment below if you have a question about a term that’s not listed or you wish to suggest an addition or edit to the glossary.

What is:

Apex = the point where the two slopes of the roof meet at the ridge. The tallest point of the building.

BMT = Base Metal Thickness is a term to describe the thickness of the metal used not including coatings or paint. The thickness of your sheeting will affect the price of your building. Thicker sheeting costs more.

BOM = Bill of Materials, In the building Industry a bill of materials or B.O.M is a list of the components, parts and the quantities of each needed to construct the end product.

Cee section = steel purlin that is shaped in a C. Portal Frames are often constructed with them. Wall Girts and Roof Purlins often use Cee section.

Column = vertical steel post usually a Cee section that is part of the main building frame and supports the rafters and eave purlins.

Cross Bracing = steel strap or threaded rod bracing used on larger buildings or buildings in higher wind.

Diaphragm Bracing = refers to the bracing effect that the roof and wall sheeting have on the building. Smaller buildings only require the bracing effect of the sheeting in certain regions.

Downpipes = usually supplied with most building kits in the form of rectangular Colorbond or Zincalume pipes. If you are planning to run your rainwater from the building to a tank straight away then you may consider asking for these to be taken out of the kit and use Poly pipe instead.

Eave = found at the lower edge of the roof slope usually at the top of the side walls and where the gutters are normally located. Eave height is another method to describe the height of the building.

Engineering = when purchasing a building you should be issued with documents that certify the structural integrity of your building. This engineering should be generated specifically for your building, based on your site conditions and use of your building and are required for certification processes by council or a private certifier.

Engineering Step = changing a span or wall height affects the required engineering. As these change in size so does the engineering and therefore the size and thickness of structural materials. The change from one thickness or size of a structural member to another is referred to as a step or engineering step. 

Frame = the main structure of your building to which the cladding/sheeting and the doors and windows are attached to.

Importance Level = the level of consequences in the event of a building failure.  

PA door = Personal Access door.

Portal Frame = the section of your building consisting of your 2 columns, 2 rafters, 1 apex and 2 knee brackets. The area between two portal frames is called a bay.

Purlin = a horizontal structural member that supports the roof sheeting. In buildings they are usually a Cee or Zed section.

Pitch = see roof pitch.

Rafter = a rafter is a sloped beam, usually Cee section, that extends from the ridge or apex down to the eave and connects to the column usually at the eave, designed to support the roof and its associated loads.

Roof Pitch = The angle or slope of the roof sheeting, 10 and 15 degree roof pitches are the most common in Domestic garages. Your building supplier will likely have more options available.

Site Specific Engineering – This ensures your home will be designed to accommodate the land it’s going to sit on. Engineers will look at the topography of the ground, the terrain of surrounding areas, and local weather conditions before signing off on any project.

Skillion = single low pitch roofed structure.

Span = in building talk it’s usually the distance between two main columns and is most often referenced as the width of the building across the end wall (gable end of building). Also refers to covering the distance between 2 points.

TCT = Total Coating Thickness is a term used to describe the overall thickness of a coloured or coated sheet steel like Colorbond. This figure includes the Base Metal Thickness plus the paints or coatings.

Tek screw = usually a self tapping self drilling screw with a Hex head. They come in various sizes and are used in various situations on your building. You should ensure that the ones that are used on the walling and roofing and flashings have a neoprene washer for waterproofing. 

Terrain = refers to the surroundings where you will build.

Wind Speed = Wind speed is a common factor in the design of structures and buildings around the world. The wind speed is a governing factor in the design of a structure and is used by professional engineers and designers. 

Zed section = Z shaped profile steel purlin often used as roof purlins and wall girts due to their ability to lap.