Shea CullenNSW Registered Architect 9748 · Updated 23 August 2026A well designed addition is often better value than moving: you keep the street, the neighbours and the land you already own, and you spend the money on the house rather than on stamp duty and agents.
The trick is knowing which approval pathway your project falls under before you design it, because that decides the cost and the timeline. Some additions are exempt development, some are complying development, and some need a full development application. To see what considered additions look like on real homes, have a look at the Tormina kitchen renovation and our Northern Light extension at Erina. Then work through the checklist below.
What the consultants cost
These are the approximate figures we see on a typical addition on the Central Coast. They move with the size of the job and the difficulty of the site, so use them to set a starting budget, then get a quote.
- Survey: about $2,000
- Geotechnical report: about $2,000
- Stormwater design: about $2,000
- BASIX certificate: about $1,000
- Structural engineering: about $3,000
- Certifier for the Construction Certificate: about $2,000
That is roughly $12,000 of consultants to get from an idea to a Construction Certificate. Architectural fees, council lodgement fees and any extra reports your site triggers, an arborist or a bushfire report for example, sit on top of that. Each figure appears again on the step it belongs to. Construction itself is a separate budget, see what it costs to build on the Central Coast. For what these fees come to on a real job rather than as estimates, a client has let me publish every invoice from her build, where design, approvals and consultants totalled $50,929.70.
To see where this process can land, have a look at the kitchen renovation at Tormina and the Northern Light extension at Erina, two additions we designed on the Central Coast. You can also explore the Reeves Street extension at Narara, Blackstone at Niagara Park, The Wing at Lisarow, The Retreat at North Gosford, the Charmhaven sustainable retrofit and the Old Managers Cottage at Narara Ecovillage. For the bigger picture, from feasibility through contracts to construction, see before you build on the Central Coast.