Planning an open plan renovation in Adelaide

Floor plans and approval questions for an open plan renovation

Whether an open plan renovation requires development approval, and which consents are involved, is confirmed for that address with the council and, for building rules consent, with the building certifier where one is engaged.

Where a development application is lodged, PlanSA’s development application checklist states, under floor plans, that “alterations to existing buildings should indicate proposed changes to the structure and what is being retained.” Separately from any application, the brief for an open plan renovation can set out where the kitchen, dining and living areas end up, how people move through them, and where storage that sat against the old wall goes.

• Structural renovations and extensions
• Home extensions in Adelaide

Beams and posts when opening up a wall

YourHome states that “you will need a qualified structural engineer to design any structural modifications.” Where a wall between two rooms carries roof, ceiling or floor load, the engineer’s design sets what replaces it, described in general terms as a beam across the opening, the supports at each end, and whether the footings beneath them need to be new or strengthened. Whether a whole wall comes out or a wide opening is formed in it is part of the same design question.

The note on removing a load-bearing wall covers how load-bearing walls are identified, what replaces them, and whether a beam can sit within the ceiling.

• Removing a load-bearing wall in Adelaide

Knocking walls through in a villa, bungalow or 1950s–60s house

The age or style of a house does not say on its own how a particular wall was built or what it carries; that is established by looking at that house. What the era does bear on is materials. SafeWork SA’s guide for home renovators states that a home built or renovated before the mid-1980s is “highly likely” to have asbestos-containing products, between the mid-1980s and 1990 “likely”, and after 1990 “unlikely”, and lists the kitchen, bathroom, laundry and under-floor coverings among the places they are found.

SafeWork SA advises: “If in doubt, get the material tested or assume it is asbestos.” Establishing that before a wall or floor covering is disturbed is part of planning the work.

Plumbing, electrical and gas services in the wall

A kitchen wall can carry water supply, drainage and a gas line as well as wiring. The South Australian Government’s page on planning a new home or renovation advises: “always use licensed tradespeople for building, electrical, gas and plumbing work.”

If the renovation relocates a sink, dishwasher or gas cooktop, the new positions need suitable routes for drainage and supply. An island needs services under or through the floor only where its design includes serviced fixtures, and that is a different job on a timber floor than on a concrete slab.

Floor level differences and ceiling heights between rooms

Two rooms that were built separately may not share a floor level, a floor structure or a finish. Whether they are brought level, joined with a threshold or replaced as one surface is a design decision made with the condition of the floor framing in view.

Ceilings raise the same question. Clause 10.3.1 of the NCC 2022 Housing Provisions sets heights of not less than 2.4 m in a habitable room excluding a kitchen and 2.1 m in a kitchen, and for a habitable room other than an attic with a sloping ceiling or projections below the ceiling line, 2.4 m over two-thirds of the floor area (parts lower than 1.5 m are not counted). How a bulkhead over a new beam is treated under these provisions, which provisions apply to altered rooms, and under which edition, is for the building certifier or council assessing the work.

Natural light and ventilation when rooms are combined

Clause 10.5.1 of the NCC 2022 Housing Provisions requires natural light to all habitable rooms. Clause 10.5.1(2) sets it by aggregate light transmitting area, “measured exclusive of framing members, glazing bars or other obstructions”: windows of not less than 10% of the floor area of the room, roof lights of not less than 3%, or a proportional combination of the two. Clause 10.5.1(4) allows light to come through glazed panels or openings from an adjoining room, with light transmitting area tests set against the room lit and against the combined floor area of both rooms. Clause 10.5.1(5) allows those areas to be reduced “as appropriate if direct natural light is provided from another source.”

Clause 10.6.2(b) sets separate conditions for natural ventilation through an adjoining room: neither room may be a sanitary compartment, the opening between them must have a ventilating area of not less than 5% of the floor area of the room to be ventilated, the adjoining room must have a ventilating area of not less than 5% of the combined floor areas, and those areas may be reduced where direct natural ventilation is provided from another source. Moving walls changes which rooms these provisions are measured against, for the opened space and for the rooms left behind. Which provisions apply to an altered room, and under which edition, is for the building certifier or council.

• NCC 2025 in South Australia: which edition applies

Heating, cooling, sound and sightlines in an open plan space

Two rooms that could be heated or cooled separately become one space that cannot be closed off in part. YourHome’s heating and cooling guidance notes that “zoned systems cool only occupied areas and allow different conditioning in living and sleeping areas”, and its renovation guide lists “creating zones for efficient heating and cooling” among the improvements an energy assessment can identify. Whether an existing system, sized and zoned for separate rooms, still suits the combined space is a question for the system’s designer or installer.

Sound changes too. YourHome’s noise control guidance defines reverberation as “reflected sound building up inside a room, often making hard rooms feel bright, echoey or noisy”, and states that absorptive finishes such as rugs, curtains and upholstered furniture “are not a substitute for sound isolation”. An open kitchen gives sightlines across the house and also carries its noise and cooking smells.