Attic Conversions near you

Part 10.3 of the Housing Provisions sets out room heights, and clause 10.3.1(1) gives the general rule: not less than 2.4 metres in a habitable room other than a kitchen, 2.1 metres in a kitchen, and 2.1 metres in a bathroom, laundry, sanitary compartment, corridor, passageway or garage. Stairways, ramps and landings require 2.0 metres measured vertically above the nosing line.

Sloping ceilings are treated separately. For a habitable room in an attic, the requirement is a height of not less than 2.2 metres for at least two-thirds of the floor area. For other habitable rooms with a sloping ceiling the figure is 2.4 metres over two-thirds of the floor area, and for non-habitable rooms it is 2.1 metres over two-thirds.

The measuring rule matters as much as the height. Clause 10.3.1(2) provides that when computing the floor area for the sloping ceiling requirement, any part with a ceiling height of less than 1.5 metres is not included. That has a useful consequence: the low triangles under the eaves are excluded from the calculation rather than counting against you, which is why a well-shaped attic can pass a test that seems impossible at first glance.

A prefabricated truss is engineered as a whole. The top chords carry the roof, the bottom chord carries the ceiling and ties the two rafters together against spreading, and the webs transfer load between them. Cutting a web, or removing a bottom chord to open up the space, does not simply weaken the truss; it changes the way loads travel through the entire roof and can push a spreading force out onto walls that were never designed to resist it.

Converting a trussed roof therefore means designing and installing a replacement structure, typically steel or engineered timber beams that pick up the roof loads and a new floor system that carries the occupied space. Volume Two clause H1D6 lists the deemed-to-satisfy route for framing, referencing AS 1684.2, AS 1684.3 and AS 1684.4 for residential timber framing, AS 1720.1 and AS 1720.5 for timber design, AS 4100 for steel, AS/NZS 4600 for cold-formed steel and the NASH Standard for steel framing. Any solution outside those documents is a performance solution, which needs an engineer and a building surveyor's acceptance.

This is the point where many attic projects stop, and stopping is a legitimate outcome. A dormer and a staircase in a conventionally framed roof is a renovation. Replacing a trussed roof is closer to adding a storey.

The honest comparison is not attic against nothing; it is attic against the alternatives for the same money. A roof conversion keeps the building footprint unchanged, which is valuable on a small block and in a council area with tight site coverage controls, and it leaves the garden alone. Against that, it is constrained by a geometry you did not choose, it swallows a substantial chunk of the floor below for a staircase, and in a trussed roof it carries structural costs that a ground-floor extension does not.

A useful test is to price the staircase and the structure first, before any thought is given to finishes. If those two items alone approach what a modest ground-floor addition would cost, the attic is probably the sentimental choice rather than the rational one. If the roof is conventionally framed, the pitch is generous and there is an obvious place for a stair, the arithmetic often goes the other way.