Designing a custom home in Sydney runs through five stages — brief and feasibility, concept design, design development, approval, and construction documentation — typically taking 7 to 14 months before building starts. The single biggest factor in a smooth process is having the builder involved from concept, so every design decision carries a real cost beside it.
Most clients know roughly what construction looks like. The design phase before it — where the home is actually decided — is far less visible. Here is the process as it should run.
Stage one: brief and feasibility
Before anyone draws, two documents need to exist: an honest brief (how you live, what you need, what you dream of, what you'll spend) and a feasibility study of the block — survey, planning controls, orientation, geotechnical conditions, services. This stage is cheap and decides everything after it. A month spent here routinely saves six later.
Stage two: concept design
The architect translates brief and block into a parti — the organising idea. Where the home sits on the land, how the section works, where light enters, how you move through it. Expect two or three genuine alternatives, not one scheme presented as inevitable. This is also where the builder should join: a concept tested against real cost at this stage can still change cheaply.
Stage three: design development
The concept hardens into a real building — structure, materials, windows, joinery, services. This is the highest-leverage stage of the whole project: decisions made here set 80% of the final cost. It is also where our clients make selections early, because every finish chosen now is a provisional sum removed from the contract later.
Stage four: approval
CDC or DA, depending on the design and the land. A CDC can be issued in weeks when the scheme meets state standards; a DA runs three to nine months through council with neighbour notification. The pathway should have been chosen back at feasibility — a design that needs a DA should know it from the first sketch and be drawn to earn its approval.
Stage five: construction documentation
The drawings the home is actually built from: dimensioned set-outs, junction details, schedules, specifications. Documentation quality is invisible to clients and decisive on site — incomplete drawings become improvisation, and improvisation becomes variations. Our sets are complete because our own trades build from them.
How long does all this take?
Realistically, 7 to 14 months from first meeting to construction-ready, dominated by the approval pathway. It can compress when decisions come quickly; it should never be compressed by skipping documentation.
The pattern behind a smooth process is a single accountable team — architect, builder and client making decisions together, with real numbers on the table from concept onward. That is how Merc.Build's design and planning service is built, and it is the difference between a design process and a design gamble.