Carports at the side of a dwelling and fire rating requirements

There is a lot of confusion when I talk to people about when you can place a carport at the side of a dwelling, and how the fire separation from the boundary works.

As a general rule, the National Construction Code handles all this, and if your building is setback greater than 900mm from the side boundary then you don’t require fire rated walls, but if you are closer than 900mm then you do.

Carports though have an exception in the National Construction Code. It is a little bit convoluted on how this is calculated though.

The actual definition of this is outlined below, taken straight from the NCC:

3.7.2.6 Open carports

(a) A Class 10a carport is exempt from complying with 3.7.2.5(a) if—

• (i) It has two or more sides open and not less than one third of its perimeter open; and
• (ii) For the purposes of (i), a side is considered to be open if the roof covering adjacent to that side is not less than 500 mm from another building or allotment boundary; and
• (iii) It has a polycarbonate or non-combustible roof covering; and
• (iv) Any ceiling lining and wall cladding, including gables, is non-combustible (see Figure 3.7.2.7); and
• (v) It does not provide direct vertical support to any part of the Class 1 building; and
• (vi) In the case where it has a common roof structure with the Class 1 building and the carport does not have a ceiling (See Figure 3.7.2.8), the opening between the top of the wall of the Class 1 building and the underside of the roof covering is infilled with—
  • (A) a non-combustible material; or
  • (B) construction clad with non-combustible material on the carport side.   

I have added “Figure 3.7.2.7 Identifying an open carport” and “Figure 3.7.2.8 Requirements for non-combustible infill panels to carports” below (sources National Construction Code).

I’ll unpack some of the points above for clarification.

Starting with Point (i) and (ii):

A carport can be built right to the boundary and not require to be fire rated (can be made of timber), if two sides and one third of the perimeter are “open”. Now, according to the NCC, even though the side located on the boundary is open (only has timber posts), it is considered “closed” if the roof sheeting is closer than 500mm to the side boundary.

The side attached to the house is considered “closed”.

If you add a roller door or infill a wall, this side is then considered “closed” as well.

So if you put this together, if you have 3m of room between your dwelling and the side boundary where the carport will be located, then as long as the front and back of the carport are “open” (don’t have roller doors, gates or part walls infilled), then the carport and it’s roof covering can be placed right on the boundary as long as the carport doesn’t exceed 6m in length.

This way you tick the two sides being open (front and back) and the one third of the perimeter of the carport, 3m front + 3m back = 6m “open”, and the total perimeter of the carport is 3m front + 3m back + 6m closed side on the boundary + 6m closed side against the dwelling = 18m.

This is explained in the NCC “Figure 3.7.2.7 Identifying an open carport” below.

There is a way around this though if you would like to have the carport extend longer than 6m. In this instance you would either step the carport in 500mm from the side boundary, or you can step the roof sheeting in, and still have the posts and rafters right on the boundary. An example of this is shown in the figure “Roof sheeting stepped in 500mm” below.

Points (iii) and (iv):

The definition of non-combustibility in the National Construction code if below

Non-combustible means—

1. applied to a material — not deemed combustible as determined by AS 1530.1 — Combustibility Tests for Materials; and
2. applied to construction or part of a building — constructed wholly of materials that are not deemed combustible.

Generally, this means the roof sheeting, gable material, and any ceiling lining needs to be non-combustible and generally not made of timber. Eave material such as hardiflex, tiles and colorbond roof sheeting, and any composite weatherboards are considered non-combustible.

Point (v):

Simply put, the carport can’t have a room over or anything like that. The dwelling it is attached too would need to be able to stand independently if the carport was taken away.

The figure “Carport providing vertical support” below shows a development with a room over the carport. As such, this carport needs to be set back 900mm minimum from the side boundary as it is providing vertical support for the dwelling, or in the case of the figure shown, the carport needs to have a fire rated wall (in this case a brick wall).

Point (vi):

The above generally refers to a skillion roof carport. If the carport has the main roof of the dwelling extend out over the carport, then the same conditions apply as above, but extra fire rating is required where the carport roof attaches to the existing dwelling.

This is shown below in figure “Figure 3.7.2.8 Requirements for non-combustible infill panels to carports”.

Hope this gives some clarifications on when and where carports can be built to the boundary without being fire rated.

If you have any questions regarding this, please don’t hesitate to contact us.