Lock-up is the point at which a building can be closed and secured. The roof is on, external wall cladding is complete, and external windows and doors are installed. It matters for two reasons: it usually triggers a progress payment, and it is the moment internal trades can begin without their work being exposed to weather.
Lock-up is one of the named stages in most Australian building contracts, which makes it one of the moments money changes hands. It is also one of the least precisely defined terms in the process. Two people can both be describing the same site accurately when one says the job is at lock-up and the other says it is not, because the contract wording differs and because closed and secure can be read narrowly or generously.
On a renovation or extension it gets more complicated again, because part of the building was already locked up before anyone arrived.
What is complete at lock-up
In broad terms, the external envelope is finished and the building can be locked. That means:
- Roof covering and flashings complete, including penetrations for flues, vents and skylights.
- External walls complete — brickwork, cladding or render substrate, depending on the build.
- External windows installed and glazed.
- External doors installed and lockable.
- The building actually locks. Not a figure of speech — a key turns and the building is secure.
The purpose is not aesthetic. Once an envelope is closed, plaster, insulation, timber and cabinetry can enter the building without being ruined, and materials can be stored on site rather than delivered daily. Lock-up is the moment a building stops being a construction site exposed to the sky and starts being a container that work happens inside.
What is not complete at lock-up
This is where expectations most often diverge from reality. At lock-up there is generally:
- No internal lining — walls and ceilings are still open framing.
- No waterproofing or tiling.
- No internal doors, skirtings or architraves.
- Services roughed in but nothing fitted off — no tapware, no switches, no light fittings.
- No painting, no floor coverings, no cabinetry.
A building at lock-up looks, to most people walking through it for the first time, considerably less finished than the word suggests. It is worth setting that expectation with yourself before the inspection, because the gap between the word and the sight of bare framing has soured a lot of otherwise good site visits.
Why lock-up is a payment stage
Progress payment schedules divide a build into stages that are large enough to be worth invoicing and objective enough to be verified. Lock-up qualifies on both counts. A large, expensive and highly visible tranche of work has been completed, and — importantly — the risk profile of the job has genuinely changed, because the building is now protected from weather and from entry.
The proportion of the contract sum attached to lock-up is set by the contract itself, and the way stage payments can be structured is regulated differently from state to state. Some states cap deposits and constrain how stages may be weighted. Read your own schedule rather than working from a percentage you heard somewhere, and if the schedule is front-loaded relative to the work actually done, raise it before signing rather than after.
For how the wider payment structure works, see progress payments in a building contract explained.
How lock-up works on a renovation or extension
On a new build, lock-up is unambiguous — there is one building and either it closes or it does not. On a renovation it is messier, and the ambiguity is worth resolving in the contract rather than on site.
The new portion has to tie into the existing structure, and the junction between old and new is where weather gets in. A roof that is complete over the extension but not yet flashed into the existing roofline is not weathertight, however finished it looks from the ground. Similarly, an extension that opens into the existing house through a wall that has not yet been removed may be sealed at the boundary between the two — or may be relying on the old house for its weather protection.
Good practice is for the contract to state explicitly which openings must be permanently closed, how the junction between new and existing work is treated, and whether the existing dwelling forms part of the secured envelope. Where that has been written down, lock-up on a renovation is as clear as it is on a new build. Where it has not, it becomes a conversation at exactly the moment a payment is due, which is the worst time to have it.
What to check before you agree lock-up has been reached
Treat lock-up as an inspection, not a notification. Before you release the payment:
- Read the contract's own definition of lock-up. It is the only definition that matters. Some contracts list the specific elements; some refer to a standard; some are vague.
- Walk the full external envelope. Roof covering, flashings, ridge and valley detail, cladding junctions, and every penetration through the skin of the building.
- Check every external opening. Are the windows and doors the permanent units, or temporary infill? Temporary closures are sometimes agreed and entirely reasonable — but they should be agreed in writing, not discovered.
- Check the junction between new and existing. On an extension this is the most likely place for water to enter and the most likely thing to be outstanding.
- Test that the building locks. Every external door, with a key.
- Photograph everything, dated. This takes ten minutes and is the cheapest record you will ever create.
- Put any incomplete items in writing before paying, with an agreed date for completion. A short, factual email is enough. Almost every builder will confirm it without friction; the value of having it is that nobody has to rely on memory later.
Common questions
Is lock-up the same as weathertight?
They overlap but are not identical. Weathertight describes the building's resistance to water. Lock-up adds security — the building must also be closeable and lockable. A building can be weathertight while still missing a lockable door.
Do internal doors count towards lock-up?
No. Internal doors are second-fix carpentry and arrive much later in the sequence. Only external doors are relevant at lock-up.
Does the garage door count?
It depends entirely on the contract. Garage doors are commonly excluded from lock-up because they are supplied and installed by a specialist trade on their own timeline. If the garage is part of the secured envelope in your mind, confirm it is part of it in the contract.
How long does it take to reach lock-up?
There is no useful rule of thumb, because it depends on the size of the work, the structural system, weather and whether approvals landed on time. Ask for lock-up to be shown as a date on the program rather than estimating from an average, and ask what that date assumes.
What if I do not agree that lock-up has been reached?
Raise it in writing, specifically and without delay, listing the items you consider outstanding. Most contracts set out a process for disputing a progress claim and a timeframe for doing so, and those timeframes can be short. If the amount is significant or the position is contested, get advice before the payment date rather than after.
Where to go next
Lock-up is one stage in a sequence that runs from demolition to handover, and it makes far more sense in context.
Read next: what order trades come in on a renovation — the full sequence and the logic underneath it. If your program is already slipping, why renovations run late covers what causes it and what you can control. Or start at Renovations & Extensions for the wider picture.
Home Collab publishes the working detail behind building and renovating in Australia — written from job experience, updated as methods and regulations move, and free to read.
August 15, 2026