Owner-builders carry the estimating risk a builder would normally carry for them. An independent estimate is the cheapest way to take that risk off the table before the first trade is booked.
Why owner-builders get caught out
Most owner-builder budgets are built from a handful of trade quotes plus a guess for the rest. The trade quotes are usually fine; it is the rest that hurts: the items nobody quoted because nobody was asked, the quantities that were rounded down, the preliminaries such as scaffold, bins, temporary fencing, site toilets and insurances, and the margin every builder carries for the things that go wrong. A proper estimate lists all of it, task by task, so the budget reflects the whole build rather than the visible parts of it.
What an estimate gives you
- A complete cost, itemised by stage, so you know what each part of the build should cost before you start collecting quotes.
- A yardstick for trade quotes. When a quote comes in well above or below the estimate, you know to ask why.
- Material quantities you can hand to a supplier, so you order what the drawings need rather than what a guess suggests.
- Something to show the bank. Lenders financing an owner-builder project generally want to see a credible costed budget.
When to get it done
Ideally twice. A preliminary budget from your sketch plans tells you whether the design fits the money before you pay for construction drawings. A full estimate from the construction drawings, engineering and selections gives you the working budget and the quantities. If you only do one, do the full estimate, and do it before you sign anything with a trade or a supplier.
A note on licensing and approvals
Owner-builder work in Queensland is regulated by the QBCC and, in New South Wales, by NSW Fair Trading. An owner-builder permit is required above the relevant value thresholds, and there are rules on which work you can do yourself and what must be done by licensed trades. We estimate the project; we do not advise on your permit or approvals, so check the current requirements with the regulator or your certifier before you start.
Who is doing the estimating
Cottage Estimating Services is a registered builder in Queensland and New South Wales with over forty years in construction management, supervision and estimating. We work with owner-builders across the Darling Downs and beyond, alongside project builders, designers and suppliers, so the numbers you get are the same numbers a builder would be working from.
Planning your own build? Send the plans and we will quote the estimate the same day.