The Owner-Builder’s Checklist: Can You Really Build a DIY Granny Flat?

This DIY granny flat checklist helps you decide whether to manage an owner-build before you order a kit. You need a lawful approval route, the relevant owner-builder eligibility, a complete budget and enough time to coordinate people and inspections. Assembly instructions cover only one part of that job.

Write down who will own each task. If a supplier says something is an owner responsibility, it needs a named person, a quote and a place in the programme. A blank beside foundations or electrical supply is an unresolved cost, not a saving.

Check eligibility and approvals first

Owner-builder requirements differ by jurisdiction. Use the building authority’s current rules for the property and type of work. Don’t transfer a permit threshold from another state or calculate eligibility from the kit price alone.

For example, NSW’s owner-builder guidance uses the reasonable market cost of labour and materials, including GST. A permit is required for covered work above $10,000; additional training applies at $20,000 or more. Check the other eligibility conditions and application sequence before relying on that example.

Ask the practitioner handling your approval to distinguish planning consent, building approval and owner-builder permission. They do different jobs. In NSW, a CDC can combine planning and construction approval; a DA consent does not by itself authorise construction. Read our approval guide and owner-builder permit guide for the questions to take to your authority.

Match the kit to a buildable design

Get the inclusions schedule and sample instructions before paying a deposit. Check the intended building classification, site engineering process, window specification, connection details and responsibilities for energy compliance. A factory drawing for another site is not evidence that the same design works on yours.

If the instructions assume skills or equipment you don’t have, price the help required. Steel, timber and modular systems each bring installation requirements; no material makes the management work disappear.

Compare complete budgets, not promised savings

There is no supported percentage saving to promise every owner-builder. Your own labour and coordination may reduce particular invoices, but delays, rework, hire equipment and separate trade contracts can absorb that difference. Include the value of time away from paid work.

Compare an owner-build budget with a builder’s quote for the same scope. Include design, reports, approvals, insurance, site preparation, foundations, delivery, restricted trades, internal finishes and final documentation. Ask whether GST and disposal are included. Don’t count a builder’s management allowance as a saving twice.

Use our cost breakdown to record each allowance. Base the contingency on unresolved risks, such as unknown ground conditions or incomplete service quotes, rather than treating a fixed percentage as protection against every problem.

Plan the work and inspection sequence

Build a programme with the people doing the work. Confirm which inspections must happen before concrete is poured or a wall is closed, who books them and how much notice is needed. Ask trades what must be ready before they arrive.

Allow for deliveries during business hours, weather interruptions and revisions to drawings. If a trade cannot attend, identify which later tasks must move. A promise to work every weekend doesn’t solve a missed weekday inspection or a supplier’s delivery restriction.

Maintain one current drawing set, a variation log and a record of invoices, photographs and certificates. Distribute approved changes to everyone affected. Don’t let the electrician and cabinet installer work from different kitchen layouts.

Decide what you can safely take on

Check the licensing rules for each trade package. Owner-builder permission does not authorise you to perform restricted electrical, plumbing or other licensed work. Arrange the required insurance and discuss the site with your insurer before construction starts.

If you cannot be available to coordinate the build, price professional management or a broader building contract. Compare the responsibility each option transfers as well as the invoice total. Browse the builder directory and prefab directory after establishing what your property can accommodate.

Frequently Asked Questions