Do I Need an Architect During Construction?

What Happens If You Remove Professional Oversight from Your Extension or Renovation

By the time construction begins, you have already committed significant time, money and energy. The design is complete. Planning permission is secured. A contractor is appointed.

It is at this point many homeowners pause and ask:

Do I need an architect?
Or more specifically, do I need an architect for extension work once a builder is on site?

It is a reasonable question.

Construction is where decisions become permanent. It is also where budgets shift, timelines stretch and details are either protected or diluted. The issue is not trust. It is structure.

What Does an Architect Do During Construction?

Within our framework for Architect-Led Renovations in London this stage is known as contract administration.

In plain English, architect contract administration means managing the building contract on your behalf. It ensures that what was agreed on paper is delivered properly on site.

The architect during construction will typically:

• Visit site at key stages

• Review progress against drawings and specifications

• Issue written instructions when clarification is required

• Assess and certify payment applications

• Monitor changes before they become financial surprises

It is not supervision of trades. It is independent oversight of quality, cost and process.

Where Budgets Shift Most

Many homeowners assume cost uncertainty sits in the design phase. In reality, financial movement most commonly occurs once work starts.

On residential projects, variations can add 5 to 15 percent if not carefully controlled. Complex refurbishments can see more movement where existing buildings reveal unknown conditions.

The pattern is familiar:

• A detail is interpreted differently on site

• A product is substituted without full understanding of performance impact

• A payment request includes work not yet completed

• An unforeseen structural issue requires immediate pricing

Each decision may seem small. Together they determine the final cost.

An architect administering the contract reviews claims carefully, tests variation requests and ensures that changes are instructed formally before additional sums are committed.

If you are trying to understand how overall construction costs are shaped in London, our article on Home Extension Costs in London explains how early assumptions often shift once projects reach site.

For a broader understanding of how architectural fees relate to protecting your investment across all stages, see Understanding Architects’ Fees.

Time and Momentum

Delays rarely arrive as one dramatic event. They accumulate through small unresolved issues.

A detail awaiting clarification.
A planning condition misunderstood.
A building control query not anticipated.
A decision delayed because implications are unclear.

In London, construction intersects with planning conditions, conservation constraints, party wall obligations and building regulations. If any one of these is mishandled, progress can pause.

An architect during construction understands this regulatory environment and responds quickly when questions arise. If a delay is emerging, it is identified early rather than after time has already been lost.

If you are still selecting your contractor, Choosing the Right Builder sets out how roles and responsibilities should be clearly defined before work begins.

Protecting Build Quality

Drawings are precise. Building sites are dynamic.

Even the best technical information requires interpretation. Daily decisions are made about sequencing, tolerances and substitutions.

In retrofit and extension projects, small deviations can have long-term consequences:

• Insulation installed without proper continuity

• Airtightness layers punctured and not sealed

• Junction details simplified for convenience

• Alternative products chosen without understanding durability

Moisture within building fabric increases heat loss significantly. A small shortcut during installation can undermine long-term comfort and energy performance.

The architect’s role during construction is to check that what is built matches what was designed. Where alternatives are proposed, spatial, technical and financial implications are considered before approval.

This is quality assurance in practice.

Architect vs Builder During Construction

There is sometimes confusion around architect vs builder roles at this stage.

A builder is responsible for constructing the project in accordance with the contract documents. An architect administering the contract ensures those documents are interpreted consistently and fairly.

Good builders generally welcome clarity. Clear drawings reduce dispute. Defined variation procedures reduce ambiguity. Structured payment certification protects both parties.

The presence of an architect during construction does not imply distrust. It provides definition.

When roles are clear, collaboration improves.

Managing Construction Without an Architect

It is possible to manage construction without an architect.

It tends to work best where:

• The project is modest in scope

• Technical complexity is limited

• The homeowner has construction experience

• Time is available to manage decisions daily

If you proceed without professional oversight, responsibility transfers to you. You will need to interpret drawings, evaluate payment applications, assess cost changes and manage statutory obligations directly.

For homeowners with demanding careers, the opportunity cost of this responsibility deserves consideration alongside any perceived saving.

So, Do I Need an Architect During Construction?

You do not always need one.

But you do need structure.

Construction is the stage where financial exposure and build quality are most vulnerable. Removing professional oversight reduces fees on paper. It also removes independent review of payments, formal control of changes and technical checking of what is built.

Many experienced clients retain an architect at this stage not because they doubt their builder, but because they recognise the value of defined roles and independent contract administration.

If you are planning a significant extension or renovation in London and would like clarity on how your project would be managed from first sketch to completion, our Home Visit and Appraisal offers a structured starting point.

The decision is always yours. The key is understanding what responsibility you are taking on if professional oversight is removed.