Knockdown rebuild or renovate: how to decide
Most people arrive with an answer already in mind. The house usually has an opinion of its own, and it is worth hearing before the design gets any momentum.
Start with what is underneath
The decision is rarely about the kitchen. It is about the footings, the slab or subfloor, the frame and the roof structure — the parts you cannot see and cannot cheaply change. A house with sound bones and a tired fit-out is a renovation. A house with tired bones and a lovely kitchen is usually not.
A structural engineer’s inspection is money well spent before you commit either way. Look particularly for movement cracking, signs of termite damage, undersized framing from earlier additions, and any asbestos-containing materials, which are common in Sydney houses of a certain age and change the cost of any work that disturbs them.
Can it carry what you want?
A second storey is the classic case. Adding one on top of an existing single-storey house means the existing footings and walls have to carry a load they were never designed for. Sometimes they can. Often they need significant strengthening, and the cost of that work is invisible in the finished house.
The same applies to opening up walls, lifting ceilings or relocating wet areas. Each is possible; each costs more in an old house than the same outcome costs in a new one, because it means working around what is already there.
What you are actually keeping
Make an honest list of what would survive a renovation. It is often shorter than people expect: the slab, part of the frame, some of the roof. Once you are replacing the services, the windows, the linings and the floor coverings anyway, the argument for keeping the structure gets weaker.
The opposite case is real too. Heritage character, an established garden, mature trees close to the house or a setback the current planning controls would no longer allow can all be worth more than their replacement cost — sometimes because they cannot be replaced at all.
The planning question
A new house has to meet today’s controls on height, setbacks, floor space and landscaped area. An existing house may enjoy a footprint or a position on the block that a new design could not repeat. Find out which controls apply before you decide; the planning certificate for the property is the place to start, and our article on DA and CDC covers the two approval paths.
Heritage listing or a conservation area can make demolition difficult or impossible. Check that first, not last.
The costs that do not appear on a quote
Both paths usually mean moving out. A renovation of any size makes a house unliveable for longer than most people plan for, and a rebuild certainly does. Rent, storage, and a second move are real costs, and they are the same whichever builder you choose, so put them in your own budget early.
Renovations also carry more unknowns, because nobody can see inside the walls until they are open. That uncertainty should show up somewhere — in a contingency, in provisional sums, or in a carefully written scope. A quote for renovation work that looks very certain deserves a closer read.
A rough rule
If you would be replacing most of the structure and all of the services, and the block lets you build what you want, a rebuild is usually the cleaner result for similar money. If the structure is sound and the house sits well on its land, a renovation keeps what is good about it and spends money only where it shows.
Nothing here is engineering or planning advice for a particular property. An engineer, a certifier and the council are the authorities on your house, and a conversation with each is worth having before you sign anything.