Seven Contractor Selection Mistakes That Surface Months After You Sign

Most disputes on residential and commercial projects trace back to a decision made during tendering, long before the first concrete pour.

Contractor selection tends to be treated as a price exercise that takes a week. The consequences of it, however, are lived with for a year or more. The failures below are ordinary, repeatable and avoidable, and none of them require specialist knowledge to catch.

Why these keep happening

Almost all of these mistakes share one root: comparing offers that were never describing the same project. Once the basis of comparison is unequal, the lowest number wins automatically, regardless of what it excludes.

1. Comparing totals instead of comparing scope

A single bottom-line figure is easy to read, while an itemised comparison takes hours and exposes awkward questions.

• Avoid it by: Issue one identical scope document to every bidder and require pricing against the same line items, with exclusions stated explicitly.
• Proof it is closed: A comparison sheet where every bidder has a number in every row, and blank rows are marked as deliberate exclusions.

What it costs you: The excluded items reappear as variations at non-competitive prices once the contractor is mobilised and you have no alternative.

2. Treating a licence as evidence of capability

A commercial registration and classification certificate are quick to verify and feel like due diligence.

• Avoid it by: Ask for three completed projects of similar type and size, then visit one and speak to that owner without the contractor present.
• Proof it is closed: Written references with contact details, plus your own site visit notes.

What it costs you: Registration says a company exists. It does not say the team has delivered your building type, in your city, at your quality level.

3. Accepting a programme with no intermediate milestones

A single completion date looks clean and avoids arguments during negotiation.

• Avoid it by: Require a programme with dated milestones for excavation, structure, blockwork, MEP first fix, plastering and finishing.
• Proof it is closed: A signed programme attached to the contract, with an agreed monthly reporting format against it.

What it costs you: With no interim dates, slippage is invisible until the end, when the only remedy left is a dispute about the final date.

4. Linking payments to dates rather than progress

Time-based instalments are simpler to administer and contractors prefer the predictability.

• Avoid it by: Tie every payment to a verified stage of completion, certified by a supervising engineer before release.
• Proof it is closed: A payment schedule where each line names a physical deliverable and the document that evidences it.

What it costs you: You can reach sixty per cent paid against forty per cent built, which removes the leverage you need if performance deteriorates.

5. Leaving materials described generically

Specifying brands during tender feels restrictive and slows the process down.

• Avoid it by: Name a product and an acceptable alternative for every significant item, and require samples approved in writing before ordering.
• Proof it is closed: A material schedule with approved samples logged and dated.

What it costs you: Terms such as first class or equivalent are unenforceable. The cheapest compliant product will arrive, and it will technically comply.

6. No written procedure for variations

Nobody expects changes at the start, and raising the subject feels like planning for conflict.

• Avoid it by: Agree that no variation is executed before a written instruction stating cost and time impact is signed by both sides.
• Proof it is closed: A variation register with numbered entries, each approved before execution.

What it costs you: Verbal instructions get priced after the work is done, when your negotiating position is at its weakest.

7. Ignoring the supervision arrangement

Owners often assume the contractor supervises itself, or that the designer is automatically involved during construction.

• Avoid it by: Appoint supervision separately from execution and define its authority to reject work and withhold certification.
• Proof it is closed: A supervision contract with a defined visit frequency and reporting obligation.

What it costs you: Nobody independent is checking quantities, quality or progress claims, so the only inspection happens at handover when remedies are expensive.

A short check before you sign

• Do all offers price the same document, including the same exclusions?
• Have you seen a completed project by this team, not by the company name?
• Does the programme contain dated milestones you can measure against?
• Is every payment tied to certified physical progress?
• Is there a written route for variations, retention and defects?

If it has already happened

If the contract is already signed and these gaps exist, do not wait for the next dispute. Document current progress with dated photographs and a measured survey, then agree an addendum covering milestones, variation procedure and certification. Contractors generally accept an addendum that clarifies process far more readily than they accept an argument about money later.

If you are preparing to build, Domira can review your drawings, scope and contractor offers before you commit, and supervise delivery against the programme and specification you agreed.