Reviewed 7 October 2026. This guide updates our earlier discussion of site costs. Older dollar breakdowns have been removed; use the current calculators and a property-specific written quote.
An advertised granny flat price is useful only when you understand its scope. Before comparing quotes, check the design, finishes, approval work, site work and exclusions that each price covers.
What are granny flat site costs?
Site costs are the work needed to prepare your property and connect the proposed home to its services. Depending on the site and scope, they can include:
- Excavation, foundations, piers, retaining work and soil disposal.
- Water, sewer and electricity connections, and any required upgrades.
- Stormwater drainage and rainwater systems specified for the project.
- Access arrangements and construction equipment needed to reach the building area.
- Demolition, removal of existing structures and protection of existing assets.
The amount depends on your block and proposal. A steep site, rock, restricted access, affected sewer assets or a complex drainage solution can change the required work. There is no single site-cost percentage that applies to every granny flat.
Compare the same scope in each quote
Ask for a written schedule of inclusions and exclusions. Compare the same floor plan, finishes, services and site assumptions, rather than only the headline total.
- Plans and specifications: identify the drawings and specification on which the price is based.
- Site work: check the allowed excavation, soil disposal, foundations, drainage and service connections.
- Uncertain work: ask how rock, contaminated fill, additional excavation or an electrical upgrade would be assessed and priced if required.
- Finishes: distinguish the quoted standard inclusions from optional upgrades shown in project photographs.
- Approvals: identify which design, reports, applications and fees are included or separately priced.
- Completion: clarify waste removal, access reinstatement and any landscaping or external works included.
Check the project’s BASIX commitments
Check the requirements of the relevant BASIX certificate against the proposed plans and building scope. The commitments vary by project; they are not a universal fixed-cost package. The NSW Planning Portal explains how BASIX commitments form part of the planning approval process.
Ask who is responsible for each specified item, such as the water system, glazing, insulation or hot-water equipment, and confirm its inclusion in the agreed scope.
Read the agreement and timetable
Check that the written agreement reflects the quote and the plans you have selected. Discuss exclusions, allowances, variations, payment stages and the expected programme before committing. Weather, deliveries and site conditions may affect the construction timetable; ask how changes will be handled.
Use current approval and building estimates
Our approval price calculator estimates approval work. Our building price calculator estimates the selected build and options. They cover different stages; review the selected scope and confirm property-specific work in the written quote.
Explore the Sydney granny flat cost guide and completed project case studies to see how design and site constraints affect a project.
We coordinate your design, approvals and building processes. Talk to our team about your block, layout and budget before relying on a headline price.
