Who Does What: Understanding Roles on a London Renovation Project

One of the most common sources of cost and programme overrun on London renovation projects is unclear roles. When it is not clear who is responsible for coordinating trades, who approves variations, who manages the construction programme, and who is the client's primary point of contact, things fall through gaps. This guide sets out the standard roles on a renovation project, what each covers, and how they interact.

The architect

The architect's core role is design: translating the client brief into a scheme that is buildable, regulatory-compliant, and well-resolved in spatial, aesthetic, and technical terms. In the standard RIBA Plan of Work, the architect leads from inception (Stage 0/1) through to technical design (Stage 4), then takes a reduced role during construction (Stage 5) providing periodic inspections and answering design queries from the contractor.

What the architect does not do, in a standard appointment: manage the construction programme day-to-day, manage subcontractor relationships, or take responsibility for the contractor's work quality. The architect inspects but does not supervise. This distinction matters — a client who assumes the architect is managing the contractor is likely to be disappointed.

Some architects offer a fuller project management service as an additional appointment, taking on programming and contractor management. This is worth discussing explicitly at appointment, particularly for projects without a dedicated project manager.

The project manager

A dedicated project manager (PM) — distinct from the architect and contractor — takes responsibility for programme, budget, and day-to-day coordination. On a complex London renovation project of, say, £500,000+, a PM is usually justified. On a straightforward single-room refurbishment, it is not.

The PM's role includes: setting up and maintaining the project programme, chairing site meetings, tracking costs against budget, coordinating information flow between design team and contractor, managing change control, and reporting to the client. A good PM acts as the client's eyes on site and catches problems before they become expensive.

PMs charge either a percentage of construction cost (typically 4–8%) or a fixed fee. The investment is typically recovered in programme savings, variation management, and early problem identification.

The quantity surveyor

The quantity surveyor (QS) — sometimes called a cost consultant at the early stages — handles cost management. Before construction, the QS prepares the bill of quantities (a detailed breakdown of work items used for tender), analyses tender returns, and advises on contractor selection. During construction, the QS assesses interim payment applications, manages the valuation of variations, and prepares the final account.

On a project with a tight budget or a complex scope, a QS is valuable. Without one, the client is dependent entirely on the contractor's cost reporting, which is a one-sided information source.

The structural engineer

The structural engineer designs the structural elements of the project: beam and column specifications, foundation design, connection details, and — where required — structural calculations for building control. On a London renovation involving removal of load-bearing walls, basement construction, or structural alterations, the structural engineer's input is essential and non-negotiable.

The structural engineer's responsibility ends with the design, not the execution. Site inspections at key structural stages (pouring foundations, installing beams, completing structural connections) are additional appointments that must be agreed at the outset.

The CDM principal designer

The Construction (Design and Management) Regulations 2015 require all projects with more than one contractor to appoint a Principal Designer. In practice on most London renovation projects, the architect takes this role. The Principal Designer coordinates health and safety information between the design team during the pre-construction phase and produces the pre-construction health and safety file.

Clients have duties under CDM too — primarily to appoint competent designers and contractors. On a domestic project, the client's duties are substantially discharged when the Principal Designer takes on CDM responsibility, but the client cannot avoid them by simply being unaware.

The main contractor

The main contractor is responsible for delivering the construction works described in the contract. This includes: providing and managing labour (directly employed and subcontracted), procuring and managing materials, maintaining the programme, maintaining a safe site, and producing the required quality of work.

The main contractor's responsibilities do not include: designing the project (unless on a design-and-build contract), making planning applications, or managing the client's budget against the overall project scope. These common misconceptions lead to disputes when the contractor's scope and the client's expectations diverge.

On smaller projects: the principal contractor model

On a project in the £100,000–£500,000 range, a single principal contractor who provides all trades (including specialist subcontractors) under a single appointment is the standard model. The client has one point of contact and one set of contractual obligations. The contractor coordinates the programme and trades. The risk is that the client has limited visibility of costs and programme unless a QS or PM is also appointed.

Contract forms

A written contract — even on a smaller project — is essential. Common forms:

• —JCT Minor Works Building Contract: Standard for projects up to approximately £500,000. Clear, well-understood by contractors, includes payment, variation, and dispute mechanisms.
• —JCT Intermediate Contract: For more complex projects with specialist subcontractors.
• —JCT Design and Build Contract: Where the contractor takes design responsibility.

An unsigned letter of intent or an exchange of emails is not a contract in the sense that matters when disputes arise. Use a standard form.

ASAAN acts as principal contractor on whole-property London renovation projects, coordinating all specialist trades under a single appointment and providing regular programme and cost reporting to clients. If you are assembling a project team, contact us to discuss how our model integrates with your design team.