Whether building on your own land, extending a rear kitchen or renovating a whole second-hand house, choosing a contractor affects money, time and the quality of your home for decades. The familiar stories: deposits taken and jobs abandoned, substandard work, or mid-job demands that blow the budget. Most of these are preventable with a good selection process and contract — both of which owners control from the start.
Contractors quote accurately when drawings and specifications are clear. New builds or structural extensions need architectural and structural drawings by an architect and engineer, which are also required for the building permit. For renovations, list the work room by room and specify materials — brand and model of tiles, sanitaryware, cables. The clearer the detail, the more comparable the quotes.
A bill of quantities itemises every element — material type, quantity, unit rate and labour. With BOQs from several bidders you can instantly see who under-measured, who priced different grades, or who left work out. When variations arise during construction, the BOQ provides a fair basis for pricing them. A one-line lump-sum quote leaves the owner at a disadvantage in every negotiation.
The cardinal rule: money paid must never run ahead of work completed. An example schedule for a new house:
| Instalment | Work completed and inspected | Note |
|---|---|---|
| Advance | Contract signed | Keep it small; consider requiring an advance-payment guarantee |
| Foundations | Piles, footings, ground beams | Check pile count and test results against drawings |
| Structure | Columns, beams, slabs on every floor | Inspect rebar before each pour |
| Roof and walls | Roof frame, roofing, masonry | Check waterproofing and wall alignment |
| Systems | Electrics, plumbing, sanitation | Pressure-test pipes; test circuits |
| Finishes | Plastering, flooring, painting, doors and windows | Check workmanship against specification |
| Final | Handover with all defects fixed | Deduct the retention |
For structural milestones, have an engineer you hire yourself do the inspection, not only the contractor's engineer.
Scope referenced to the drawings and BOQ as attachments; contract price and payment schedule; start and completion dates; daily penalties for contractor-caused delay; retention, typically a share of the price returned after the warranty period; warranty length; responsibility for building permits, site safety and damage to neighbouring property; a variation procedure requiring written agreement with price before work proceeds; and termination terms if the contractor abandons the job.
Visit regularly, photograph progress weekly, keep delivery notes, check delivered materials match the BOQ specification, and record every variation in writing. Changing your mind mid-way is normal, but verbal agreements cause almost all end-of-job money disputes.
No. Large advances remove your leverage if the contractor walks away. If special materials must be ordered, consider paying the supplier directly yourself.
Lump-sum with a clear BOQ is convenient and easier to budget. Buying materials yourself and hiring labour only gives material quality control, but you must manage ordering and bear shortage or surplus risk.
Document the completed work with photos and an engineer's valuation, send warning and termination notices per the contract, hire a new contractor to finish, and claim damages under the contract. A good contract and payments that never ran ahead of work keep losses limited.
Good contractors exist, but good systems matter more than trust: clear drawings and scope, BOQ comparisons, payments tied to inspected milestones, retention, and every change in writing. Read more about building permits and legal extensions on the MyProperty blog.
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