Renovation budget for a 45 m² studio in Sydney (3 bed)

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LightStory

Construction professional
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I have already put together a preliminary scope and a budget of A$123,400 for this 45 m² Sydney studio. Kitchen and bathroom work, flooring, painting, electrical checks and some energy improvements are included. There is no planned extension, but what remains unclear is the work hidden behind linings and beneath floors.

Before setting the contingency, what investigations would give the best indication of plumbing access, moisture damage and the difference between checking the electrics and rectifying them? For example, if a pipe can only be reached by opening a common wall or fitted cabinet, I want the quote to say who provides access and who makes good afterward.

Finishes can be adjusted. The greater concern is an exclusion or sequencing problem that only appears after demolition, including any unexpected structural work.
 
At this stage I’d allow roughly 15–20%, then revisit it once the intrusive checks and contractor scope are complete. The percentage matters less than identifying what can trigger it. Ask where plumbing can actually be reached, whether electrical work is inspection-only or includes rectification, and exactly what happens if moisture damage appears after demolition.
 
A few missing facts could shift that answer: is this in a strata building, how old is the building, and how many bathrooms are actually involved? Also, is “3 bed” in the heading a typo? It doesn’t line up with a 45 m² studio, so contractors need one consistent brief and measured plan.
 
I’d make each tender show the sequence, not merely a total price. For example: investigations, approvals, ordering, isolation, demolition, rough plumbing/electrical, waterproofing, finishes and final checks.

Then ask who pays for access panels, protection of common areas, disposal, making good after hidden services are exposed, and return visits caused by another trade. Those gaps are where a tidy quote can unravel.
 
The immediate constraint is that a percentage reserve cannot tell you who owns an undefined risk. Before applying 15–20% to the A$123,400, split every quote into firm inclusions, allowances and exclusions.

Then use two branches. If plumbing access and electrical rectification can be investigated and priced now, put them into the scope. If they genuinely cannot be established until opening-up, keep a stated allowance plus contingency and agree who authorises the extra work. A contingency is still sensible, but spending it is hard to reverse once demolition has started.
 
Moisture deserves its own pre-start investigation. Ask where readings will be taken, whether the bathroom edges and kitchen plumbing points can be inspected, and what evidence would trigger more opening-up. Also establish who decides whether damaged substrate is patched or replaced. Otherwise demolition stops while everyone debates responsibility.
 
One addition: connect that investigation to ordering. Cabinets, flooring and bathroom materials should not be released against dimensions or levels that may change once linings come off. The builder should identify which items can safely be ordered early and which need site confirmation, even if waiting affects the programme.
 
A large contingency still won’t protect the schedule if the studio becomes unusable halfway through. I’d ask for decision points: what findings stop work, who prices the variation, and how quickly you must approve it. A small space also gives trades little room to overlap, so an optimistic programme based on everyone working simultaneously may be unrealistic.
 
Thanks—this is helping separate uncertainty from ordinary cost. The working scope is the 45 m² studio; the “3 bed” wording is not part of the renovation scope and I’m checking why it appears. I don’t yet have enough confirmed information on building age, access arrangements or applicable strata requirements.

I’ll ask for the A$123,400 to be recast as firm inclusions, allowances and exclusions, with investigation and ordering points shown in the sequence.
 
Access arrangements could materially affect that sequence. If it is an apartment, ask about lift bookings, permitted working times, delivery size limits, protection, waste removal and where materials can be stored. Don’t assume the contractor has included those logistics. On 45 m², storing a kitchen or flooring too early could obstruct the next trade.
 
Permit timing should sit on the programme as a dependency, not as a vague note saying “if required.” Ask the contractor to list every proposed alteration that might need approval, then confirm the applicable route with the relevant Sydney council, certifier or strata contact. Requirements depend on the actual work and building, so get that settled before relying on a start date.
 
Given your update, I’d commission or request three focused investigations before final pricing: visible moisture assessment, mapping of accessible plumbing routes, and an electrical assessment that distinguishes safety checks from upgrade work. If the building’s age or records raise concerns about hidden materials, ask whether testing is needed before demolition. Feed the same findings to every bidder.
 
When comparing tenders, insist that exclusions appear beside the related work rather than buried at the end. Kitchen plumbing should state access and reinstatement; flooring should state substrate preparation; painting should state repairs; electrical should state the assumed number and condition of circuits. That makes different assumptions much easier to spot.
 
The energy upgrades also need sequencing discipline. Ask whether any insulation, sealing, ventilation or electrical items require walls or ceilings to remain open. Doing those after plastering or painting creates avoidable rework. I would keep them as separate priced items until their access requirements and any approvals are understood.
 
My practical next step would be a short pre-tender risk schedule: unknown condition, proposed investigation, responsible party, cost allowance, decision deadline and programme effect. Attach it to the drawings and scope sent to contractors. Once the major unknowns have evidence behind them, choose the contingency; before that, a percentage alone gives false precision.
 
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