Construction Stage Coordination: Your Architect's Role on Site

Many homeowners assume the architect's job is essentially done once the builder starts on site. In reality, the construction stage is when an architect's involvement can make the greatest difference to the quality, cost, and smoothness of your project. Understanding what your architect should be doing during this phase — and what they won't be doing — helps you get the most from the relationship.

Site Visits vs Full-Time Inspection

The first and most important distinction is between periodic site visits and full-time site inspection. Almost no residential project in the UK uses full-time inspection — it would mean an architect or their representative being on site every working day, and the cost is prohibitive for all but the largest houses.

Instead, residential architects carry out periodic site visits, typically fortnightly or monthly, depending on the project stage and complexity. During critical phases — foundations, structural steelwork, waterproofing — visits may be more frequent. During straightforward phases, less so.

This means the architect is not supervising the builder's work in real time. They are checking progress at intervals, reviewing quality, and addressing design questions. The contractor remains responsible for managing their own workforce, programme, and day-to-day quality control. This distinction matters because it defines who is accountable for what.

For residential projects in the Hampstead and north London area, where construction costs are high and the margin for error is slim, regular site visits are strongly recommended. Skipping this stage to save on architect fees frequently costs more in the long run through quality issues, misinterpretations of drawings, and contractor variations that go unchallenged.

What Happens During a Site Visit

A typical site visit by your architect will include:

Progress review — walking the site systematically, checking that work completed since the last visit matches the approved drawings and specification. This includes structural elements, dimensions, material choices, and finish standards.

Quality inspection — examining workmanship at a reasonable level of detail. Are brickwork courses level? Are window reveals straight? Are finishes to the expected standard? The architect won't check every screw, but they'll spot systemic quality issues and raise them with the contractor.

Reviewing contractor queries — construction inevitably throws up situations not fully covered by the drawings. A pipe run clashes with a beam. The specified tile is discontinued. The ground conditions differ from the survey. The architect resolves these on site where possible or takes them away for a considered response.

Issuing architect's instructions (AIs) — formal written instructions that authorise changes to the works. These might confirm a material substitution, adjust a detail, or respond to an unforeseen condition. AIs create a documented trail that protects both you and the contractor, and they form the basis for any cost adjustments.

Recording the visit — a written site visit report, usually issued within a few days, summarising what was inspected, any issues found, instructions given, and actions required before the next visit. These reports are your primary record of what happened during construction.

Architect's Instructions and Variations

Changes during construction are inevitable. No set of drawings, however detailed, can anticipate every situation on a live building site. The question is how changes are managed.

Your architect acts as the gatekeeper for variations. When the contractor proposes a change — different material, adjusted detail, revised sequence — the architect evaluates whether it's acceptable in terms of design quality, building regulations compliance, and cost. If a change has cost implications, the architect should seek your approval before issuing an instruction authorising it.

This is a critical function. Without an architect reviewing variations, contractors may make pragmatic site decisions that compromise the design intent or that accumulate into significant unplanned costs. The cost of architect's construction stage services typically pays for itself many times over through the variations they prevent or negotiate down.

Reviewing Samples and Mock-Ups

For anything visible in the finished building — bricks, mortar colour, floor tiles, kitchen units, ironmongery, paint colours — your architect should be reviewing samples and, for critical elements, requesting on-site mock-ups before the contractor proceeds at scale.

This is particularly important in conservation areas across Hampstead, where the local authority may have conditioned specific materials as part of the planning approval. Getting a brick or roof tile wrong can mean stripping back completed work — an expensive and demoralising outcome. A sample panel built on site, reviewed by both you and the architect, prevents this.

Certifying Interim Payments

Under standard building contracts (JCT Minor Works or Intermediate, commonly used for residential projects), the architect has a formal role in certifying the contractor's interim payment applications.

The process works like this:

1. The contractor submits a payment application, typically monthly, stating the value of work completed to date.
2. The architect visits the site, assesses whether the claimed progress is accurate, and issues a certificate confirming the amount due.
3. You pay the certified amount within the period specified in the contract (usually 14 days).

This certification process protects you from overpaying for incomplete or defective work. The architect's certificate is an independent, professional assessment of what the contractor has earned — not simply rubber-stamping whatever the builder claims.

If there are defects or incomplete items, the architect deducts these from the certified amount or withholds payment for specific elements until they're rectified. This gives you powerful contractual leverage without putting you in the uncomfortable position of personally disputing invoices with the builder.

Contractor Queries and RFIs

Requests for Information (RFIs) are formal queries from the contractor to the architect, seeking clarification on drawings, specifications, or design intent. On a well-run residential project, you might see anywhere from a handful to several dozen RFIs, depending on complexity.

Common RFIs on north London residential projects include:

• Clarification of junctions between new work and existing Victorian fabric.
• Confirmation of precise fixing details for bespoke joinery or metalwork.
• Resolution of clashes between architectural, structural, and mechanical/electrical designs.
• Queries about how the design meets Building Regulations requirements in specific situations.

Your architect should respond to RFIs promptly — delays in answering queries can stall work on site, and contractors are entitled to claim time extensions (and sometimes costs) for delayed information. Good architects maintain a log of all RFIs, responses, and any resulting architect's instructions.

Practical Completion

Practical completion is the formal point at which the building works are deemed sufficiently complete for you to occupy and use the building. It doesn't mean every last detail is finished — minor defects (snagging items) can remain — but it means the building is safe, functional, and substantially complete.

Your architect makes the judgement call on when practical completion has been achieved and issues a practical completion certificate. This certificate triggers several important contractual events:

• The defects liability period begins — typically six or twelve months, during which the contractor must return to fix any defects that appear.
• Half the retention is released — a percentage of the contract sum (usually 2.5–5%) is held back during construction as security. Half is released at practical completion, with the remainder held until the end of the defects period.
• Your responsibility for insurance typically transfers — meaning you become responsible for insuring the building from this point.

Getting practical completion right matters. Issuing it too early leaves you living with defects and weakens your contractual position. Refusing to issue it when the work is substantially complete is unfair to the contractor and can create legal disputes.

Snagging

Snagging is the process of identifying and recording defects and incomplete items for the contractor to rectify. Your architect will prepare a formal snagging list following a detailed inspection, typically at or just before practical completion.

A snagging list on a residential project might include items such as:

• Paint touch-ups and scuffs from construction activity.
• Doors that don't close or latch properly.
• Sealant lines that are uneven or incomplete.
• Grout that's cracked or missing in tile work.
• Services that aren't commissioned correctly — a radiator that doesn't heat, an extractor fan wired to the wrong switch.

Your architect should inspect the contractor's snagging remediation work and confirm when items are satisfactorily resolved. Only when all snagging is complete should the final retention payment be released.

Retentions and Final Account

The final account is the agreed total cost of the project, accounting for all variations, provisional sums, and adjustments. Your architect assists in negotiating the final account with the contractor, ensuring that claimed costs are fair and that any deductions for defective work are properly applied.

The remaining retention money is released once the defects liability period expires and the architect confirms that all defects raised during that period have been addressed. This final payment closes out the contract.

Is Construction Stage Involvement Worth the Cost?

For residential projects with a construction value above approximately £100,000 — which covers most extensions and renovations in the Hampstead area — the answer is almost always yes. The architect's construction stage fee (typically 15–20% of their total fee) buys you independent quality oversight, professional contract administration, proper cost control, and a documented record of the entire build process.

We connect homeowners across Hampstead and north London with architects who provide robust construction stage services. It's one of the most important factors in a successful project outcome — and one of the most commonly overlooked when appointing an architect.