Short answer: A home addition quote should describe enough of the scope that you can understand what is included, what is excluded and what may still change the price.
General information: This content is general in nature and is not legal, financial or property-specific advice. Check current requirements and seek advice about your circumstances where needed.
The total number is important, but it is not enough on its own. Two proposals can look very different in price simply because one includes work that the other has left out or treated as an allowance.
Look for a clear scope of work
The quote should identify the major construction work: demolition, structural work, new walls and roof, windows and doors, services, internal finishes, external finishes and the work required to connect the new area to the existing home.
Check allowances and selections
Items that have not been fully selected may be represented as allowances. Ask what is included, how the allowance was calculated and what happens if the final selection costs more or less.
Check exclusions
Exclusions matter because they show which parts of the finished project remain the owner’s responsibility or will need to be priced separately. Landscaping, painting, floor finishes, appliances, air conditioning or utility upgrades are examples that can vary between contracts.
Understand approvals and professional fees
Confirm whether design, engineering, planning submissions, certification and other professional services are included in the proposal or handled separately.
Understand variations
Ask how changes will be agreed, documented and priced, including their effect on the overall contract. The NSW Government provides current guidance on residential building contracts and variations. A clear scope helps everyone understand the work initially included.
For more context, see Why choose fixed-price home extensions? and How to choose a home addition builder.
Talk to Wal Robbins if you have plans or a project brief and want to discuss how the scope would be developed.