An extension joins new work to an existing house, and the two parts have to work together: the house that is already there and the part being added to it. Most of what shapes an extension in Adelaide is settled before anything is drawn — what the brief needs the new space to do, what the existing structure and ground can take, and what the address allows.
Start with what the extension has to do
A brief for an extension is more than a floor area. It is which rooms are added, how they connect to the rooms that stay, which way they face, and what happens to the parts of the house the new work passes through. A new living area at the rear often changes the kitchen and hallway as much as it adds space.
Writing down which parts of the existing house the brief keeps, changes or removes is the most useful early step. It is the list that later decides how the work is built, what has to be opened up, and whether an extension is still the right path at all.
Light and air for the rooms that stay are part of the brief too. An extension built across the back of a house can take the windows that currently light the kitchen or living room, and those rooms then depend on the new space for daylight and ventilation.
Where the new meets the old
The junction between the extension and the original house is where much of the design and site effort goes. Floor levels have to meet or step deliberately. Roof lines have to join without creating a place for water to collect. Wall thicknesses, ceiling heights and window heads rarely line up on their own.
Making an opening in an existing external wall to connect the two parts is structural work in its own right. What that wall carries, and what replaces it across the opening, is established for that house rather than assumed.
Services cross the junction too. Power, water, drainage, heating and cooling for the new rooms either extend from the existing house or are brought in separately, and the condition of what is already there becomes part of the question once it is uncovered.
The junction is also where water finds its way in if the detailing is wrong. Flashings, wall wraps and the step between the old and new roofs are details that are drawn and checked, rather than left to be resolved on site.
What the existing structure and ground can carry
New footings often sit beside older footings. On reactive clay, which swells and shrinks with moisture, the old and new parts of the house can move differently, and the way the two are joined has to allow for that. The footing design for the extension is made for the site classification, typically by an engineer.
A double storey extension, or any addition that places new load on the existing house, raises a separate question: whether the existing footings and walls can carry it. That is answered by an engineering assessment of that building, not by its age or appearance. Where the answer is that they need strengthening, that work belongs in the scope.
Rear, side or upward: what changes with each
A rear extension usually has the most room to work with, but it uses the garden and changes where stormwater from the larger roof goes. Access for machines and materials past the existing house can decide how the site works are carried out.
A side extension brings the work closer to the boundary. Footings and excavation near the boundary raise questions about the neighbour’s ground.
Where the work involves a wall shared with an attached neighbour, or a new wall on the boundary line, Division 3 of Part 11 of the Planning, Development and Infrastructure Act 2016 deals with party walls; the note on party walls quotes it.
Building upward keeps the footprint but puts load through the existing structure, takes floor area below for a stair, and opens the house to the weather while the roof is off. Each of those is a design and sequencing question for that particular house.
Which of the three suits a house is often decided by what the block leaves room for and by the existing roof and structure, as much as by preference.
What applies to the address
Some constraints attach to the block rather than to the design: the zone and overlays that apply to the address, heritage listing, regulated trees, and the neighbour’s ground.
Whether a proposal requires development approval, and which consents are involved, is determined under the Act, the Regulations and the Planning and Design Code for that address; the pathway is confirmed with the council and, for building rules consent, with the building certifier where one is engaged.
These are property questions, and they are worth answering before a design is settled. The note on what can stop or reshape a rebuild sets out several provisions that attach to the block, including those on regulated trees and on access to the neighbour’s land.
Drawings, pricing and living in the house
A quote for an extension can only be as specific as the documents behind it: drawings of the new work and of how it meets the existing house, the engineer’s design, the site classification, existing levels, and the selections. Items that are not yet drawn or chosen can only be carried as allowances until they are.
Whether a household can stay in the house during an extension depends on how much of the existing house the work reaches, and on whether the occupied part can be kept safe, weathertight and serviced while it proceeds. Staging the work around occupancy changes the sequence, and that belongs in the plan from the start.
An extension opens up a building that was not designed for the work now being done to it. Inspection establishes some conditions in advance; others are only found once linings, floors or the roof are opened. A workable quote names those conditions and says how each will be established and priced.
Cyberidge carries out structural renovations and extensions in Adelaide, and variations are priced and approved in writing before the work proceeds.
Common Questions
What should I know before extending a house in Adelaide?
Four things shape an extension before it is drawn: what the brief needs the new space to do and which parts of the existing house it keeps; how the new part will meet the old at floors, roof and walls; what the existing structure and the ground can carry, established by an engineer; and what the address allows, confirmed with the council for that address.
Can my existing house take a double storey extension?
That is answered by an engineering assessment of that particular building — what its footings and walls were designed for and their present condition — rather than by its age or appearance. Whether the addition can be built on that block is a separate question for that address.
Does a home extension in Adelaide need council approval?
Whether a proposal requires development approval, and which consents are involved, is determined under the Act, the Regulations and the Planning and Design Code for that address; the pathway is confirmed with the council and, for building rules consent, with the building certifier where one is engaged. The zone and overlays that apply to the property shape what a proposal has to address; the note on what can stop or reshape a rebuild quotes several of the provisions involved.
What decides the cost of a home extension?
The brief, how much of the existing house the work reaches, how the new part joins the old, the footing design for the site, access to the work area, and conditions in the existing house that are only found once it is opened up. Quotes are comparable only when they are measured against the same brief.
Can we live in the house during an extension?
Sometimes. It depends on how much of the existing house the work reaches and whether the occupied part can be kept safe, weathertight and serviced while the work proceeds.
Thinking about extending a house in Adelaide? Start with a free initial consultation.