On any building constructed before 2000, a refurbishment and demolition survey is arranged before intrusive work begins. Where material is present, it is removed by a licensed contractor ahead of the works, identified at survey stage and priced into the programme.

Commercial Builds & Refurbishment London

Commercial construction in London: decisions that shape a buildable project

A commercial refurbishment must work for the building, its occupants and the business operating within it. We assess the relationship between the existing structure, proposed use, building services and statutory requirements before agreeing the construction specification. For London offices, retail units and mixed-use premises, this means identifying the technical conditions that affect construction access, regulatory compliance and the point at which the completed space can be occupied.

Which approvals must be resolved before commercial building work?

Planning permission, landlord consent and Building Regulations approval address different aspects of a commercial project. One approval does not automatically replace another. We work with the client’s appointed architect, surveyor and design professionals to establish the relevant construction requirements before site operations begin, including any conditions that affect alterations to existing premises.

Planning use and changes to commercial premises

In England, Use Class E covers several commercial, business and service activities, including qualifying shops, offices and restaurants. A change between activities within the same use class will not normally constitute development requiring planning permission solely because of the change of use. However, planning conditions, existing restrictions and the precise proposed activity must still be checked.

Moving between different use classes may require planning permission or a permitted development route with prior approval. External alterations can also require separate consent. We construct to the planning position established by the design team rather than treating the proposed business activity as sufficient evidence that the works are authorised.

The Planning Portal’s change-of-use guidance explains why the existing and proposed uses must be established before work is commissioned.

Where a client occupies leasehold premises, the lease and any licence to alter can affect which works may proceed and how the finished installation must be documented. Proposed structural openings, new service penetrations, changes to the building exterior and alterations to shared facilities may require approval from the landlord or managing agent.

We coordinate the agreed construction scope with the client’s surveyor or appointed representative, using the relevant consent documents and approved drawings. This helps distinguish works permitted under the construction contract from alterations that still require separate property-owner authorisation.

Commercial fit-out decision matrix: what should be confirmed before construction?

The starting condition of the building can determine whether a refurbishment proceeds as an internal fit-out or requires substantial structural and engineering work. We use project-specific checks to identify outstanding design information, operational constraints and necessary specialist input. The following matrix provides a practical framework for defining the construction scope before the final programme and pricing are agreed.

Project condition	Information to verify	Construction consequence
Existing structure	Structural drawings, existing alterations, load-bearing elements and engineering calculations where relevant.	Determines whether proposed openings, mezzanines, extensions or equipment loads require additional structural design and strengthening.
Mechanical and electrical capacity	Existing electrical supply, distribution, heating, ventilation, drainage and capacity for proposed installations.	Identifies whether existing systems can be retained, upgraded or replaced, and whether specialist service coordination is required.
Fire-safety provisions	Approved fire strategy where applicable, escape arrangements, compartmentation, detection systems and proposed occupancy.	Influences partition construction, fire doors, protected routes, service penetrations and the installation of fire-safety systems.
Accessibility and facilities	Proposed circulation routes, entrances, sanitary facilities and the applicable access requirements.	May affect door arrangements, internal levels, partition positions, sanitary layouts and other elements of the fit-out.
Occupation during construction	Required access, operating hours, occupied areas, shared services and temporary separation arrangements.	Determines whether the works can be phased safely or whether affected areas must be vacated during particular operations.

For projects involving upgrades to electrical, plumbing, heating or other installations, our building services information explains the specialist work we coordinate within the agreed scope.

When must a commercial construction project be notified to the HSE?

The Construction (Design and Management) Regulations 2015 (CDM 2015) apply to construction projects regardless of whether they meet the notification thresholds. A Construction Phase Plan is required, proportionate to the works. Formal F10 notification to the Health and Safety Executive (HSE) becomes necessary when the project meets either of two defined workload conditions.

CDM 2015 notification thresholds

Duration and workforce: construction work is scheduled to last longer than 30 working days and more than 20 people will be working on site at the same time at any point.
Total labour input: construction work is scheduled to exceed 500 person-days, regardless of whether the first threshold is reached.

According to the HSE, the commercial client has the legal duty to notify a qualifying project, although another party may submit the notification on the client’s behalf. Notification does not replace the duty to appoint competent project participants or establish suitable construction-phase arrangements.

Where we are formally appointed Principal Contractor, we coordinate the construction phase within our CDM 2015 responsibilities. The HSE guidance for commercial clients explains the appointments, planning duties and notification requirements.

How do accessibility and fire safety affect a commercial refurbishment?

Changes to partitions, circulation routes, entrances and occupancy can have consequences beyond the appearance of the finished premises. We coordinate the construction work with the approved access and fire-safety design, taking account of the building’s existing conditions. The applicable requirements depend on the type and extent of building work rather than a single standard fit-out specification.

Accessible circulation and sanitary accommodation

Approved Document M, Volume 2, provides guidance on access to and use of buildings other than dwellings in England. It addresses matters including entrances, internal circulation and sanitary facilities, with specific provisions for relevant building alterations and extensions.

For an office or retail fit-out, we coordinate the approved arrangements for door openings, changes in floor level, circulation spaces and relevant facilities. The design team must establish which requirements apply to the proposed works and existing premises.

We use the applicable specification rather than assuming that a layout suitable for one commercial unit will automatically satisfy the requirements of another. See Approved Document M: Access to and use of buildings.

Fire protection and the responsible person

Approved Document B provides guidance for satisfying relevant fire-safety requirements of the Building Regulations. The Regulatory Reform (Fire Safety) Order 2005 separately places ongoing duties on the responsible person for occupied non-domestic premises.

These obligations must not be confused. Construction work may require fire-resisting partitions, suitable service-penetration details and changes to escape routes. Once the premises are in use, the responsible person must manage the applicable operational fire-safety duties, including fire risk assessment.

We coordinate construction against the approved fire-safety specification and provide the relevant information within our contractual responsibilities. The Government’s Approved Document B guidance sets out the building-regulation framework.

What fire-safety information is required before commercial occupation?

Completion of physical construction does not remove the need to transfer essential building-safety information to those responsible for operating the premises. Regulation 38 of the Building Regulations 2010 requires fire-safety information to be provided to the responsible person where its conditions apply. This can be particularly relevant to commercial extensions and material changes of use involving fire-safety building work.

The required information concerns the building’s fire-safety design, construction and relevant installed systems. It enables the responsible person to understand, operate and maintain the premises safely. Depending on the project, the information may address fire compartments, escape arrangements, detection and alarm systems, and relevant fire-protection installations.

For an unoccupied building, the applicable deadline is no later than completion or first occupation, whichever occurs earlier. Different timing provisions apply where the building remains occupied during the work.

We coordinate the relevant contractor information and completion documentation within the agreed project scope. This supports the statutory handover process but does not replace the client’s ongoing responsibilities for fire safety and building operation.

Further information is provided in the Regulation 38 section of Approved Document B, Volume 2: Buildings other than dwellings.

What should you prepare before requesting a commercial construction quotation?

A commercial tender is more useful when it defines both the proposed building work and the conditions under which construction must take place. We assess the available information to identify outstanding technical matters before agreeing the final scope and programme. You can use the quotation form already provided on this page or submit your drawings and specification directly.

Provide the project documentation: share the latest architectural drawings, specifications and available engineering information.
Confirm the intended use: identify the type of business operation planned for the finished premises.
Supply the relevant consents: include existing planning decisions, landlord approvals and statutory documentation where available.
Describe the occupation requirements: specify whether the building must remain operational during construction.
Identify the required completion date: communicate the proposed opening, occupation or operational deadline.

We use this information to assess construction feasibility, identify necessary specialist input and develop a proposal aligned with the building’s actual condition. To discuss the project, contact Constructum Code about your commercial build or refurbishment.

Commercial Builds and Refurbishment in London

Constructum Code builds commercial projects across London as main contractor — offices, retail units and mixed-use premises. We take on extensions and structural alterations, full refurbishment and reconfiguration, mechanical and electrical replacement, and fit-out, on a single contract.

We work under JCT — Minor Works on straightforward schemes, Intermediate where there are named specialists or the project needs fuller contract machinery — and act as Principal Contractor under CDM 2015. Our largest contract currently on site is £900,000.

Interested in Commercial Builds and Refurbishment?

The work we take on

Commercial extensions and structural alterations

Adding floor area to a commercial building, forming or widening openings in loadbearing walls, installing steel frames, rebuilding roof structures, and inserting mezzanines. This is where a project’s real risk sits — in the structure, the foundations and the roof, rather than in the partitions.

Office and commercial refurbishment

Strip-out, reconfiguration and rebuild of a whole premises: removing internal walls to create open-plan floors, reworking circulation, and bringing the building fabric, insulation and glazing up to current standards within the same programme.

Mechanical and electrical replacement

Complete replacement of heating, power, lighting, ventilation and data, commissioned and certified, through our building services team and named specialists. On older commercial buildings this is frequently the largest single element of a refurbishment, and it determines how the building performs once it is occupied.

Retail and office fit-out

Partitions, ceilings, flooring, joinery, decoration, WC facilities and kitchens, specified and installed to commercial standards.

Change of use conversions

Converting premises between uses — retail to office, office to residential, ground-floor commercial with residential above — including the structural work and the compliance upgrades a change of use brings with it, alongside the planning consent secured by the design team.

Commercial projects

Office extension and refurbishment, Richmond TW9

A complete commercial refurbishment of an office building, combining structural work and fit-out on one contract:

Two-storey rear extension across the first and second floors
Complete demolition and reconstruction of the roof structure
Internal walls removed and the interior reconfigured as open-plan office space
Full mechanical and electrical replacement, including a new heating system and complete electrical installation
Fit-out throughout: flooring, decoration, two WC facilities and two kitchenettes
New first-floor balcony and rear terrace

Approximate construction cost: £240,000.

See the project

Currently on site

We are currently delivering a contract worth £900,000, started in September 2026 and running to a fixed 35-week programme, with a quantity surveyor and contract administrator appointed. Constructum Code is main contractor and Principal Contractor. The scheme pairs a structural extension with a specialist hydrotherapy pool installation — plant, water treatment, heating and dehumidification — delivered through named specialist subcontractors.

How we work

1. Tender and pre-construction

We price from your team’s drawings and specification on traditional single-stage tenders, and take on two-stage appointments where early contractor involvement is useful — buildability, sequencing and cost certainty developed alongside the design before the contract sum is fixed. Estimating and delivery sit with the same people, so the assumptions behind the price carry through to site rather than being rediscovered there.

2. Survey and the existing building

Existing structure, roof condition, drainage, incoming services and their capacity, and access for plant and materials. On any building constructed before 2000, a refurbishment and demolition asbestos survey is arranged before intrusive work begins. Most commercial overruns start with something found in the fabric that nobody looked for, so this stage is where the programme is protected.

3. Approvals and consents

Planning and change of use consents are secured by the design team before construction. From there we coordinate the building control route and stage inspections, the fire strategy and accessibility requirements as they apply on site, the structural engineer and any consultants each stage requires, and — on leasehold premises — the information the landlord needs for the licence to alter.

4. Contract and Principal Contractor duties

Works are executed under the appropriate JCT form, which sets out the programme, the payment schedule and the remedies for delay. Where we are appointed Principal Contractor under CDM 2015, we produce the construction phase plan, hold the risk assessments and method statements, manage site safety and the subcontract chain, and maintain the information the Principal Designer needs for the health and safety file. We carry £10m employers’ liability, £5m public liability and £1m professional indemnity, with certificates provided as standard at tender stage.

5. Construction and progress

The programme is set backwards from the date the premises need to be operational, through commissioning, finishes, services, structure and approvals, so the critical path is visible from the outset. Progress meetings and interim valuations run monthly, or more often where the programme warrants it. Variations are instructed, priced and agreed as they arise, so the account stays current rather than arriving at the end. Where the building remains in use, or neighbouring units are trading, works are phased around access, occupancy and trading hours.

6. Practical completion and handover

Snagging closed out, mechanical and electrical installations commissioned and certified, the building control completion certificate obtained, and the handover package issued: O&M manuals, as-built information, test and commissioning certificates, and manufacturer warranties on installed systems.

7. Rectification period

Defects arising in the twelve months after practical completion are made good under the contract, ahead of the final certificate and the release of retention. Structural work carries a 10-year warranty.

What a commercial project costs

Commercial projects are priced individually, because the scope varies so widely. What a refurbishment costs depends on how much of the building changes.

The main variables are:

How much structure is involved. An interior reconfiguration and a two-storey extension with a new roof sit at opposite ends of the range.
The condition of the existing services. Whether heating, power and ventilation are being upgraded or replaced entirely, and whether the incoming supply has the capacity for what you are installing.
Compliance upgrades. Fire separation, means of escape and accessibility work triggered by the scope or by a change of use.
Phased work around a trading business costs more than an empty building, because the programme is longer and the working hours are constrained.
The difference between a functional fit-out and a client-facing one.

As a reference point, the Richmond office project — a two-storey extension, a rebuilt roof, full M&E replacement and a complete fit-out — was approximately £240,000.

We price after the survey, so the estimate reflects the actual condition of the building.

Common questions

What size of project do you take on?

The Richmond office refurbishment was approximately £240,000. Our largest contract currently on site is £900,000, over a 35-week programme, with a quantity surveyor and contract administrator appointed and Constructum Code as Principal Contractor. We contract under JCT Minor Works and Intermediate, with the form set by the complexity of the works rather than the value.

How do you prefer to be appointed?

Any of the usual routes. Direct or negotiated appointment, where we survey, price and agree the contract sum with you without a competitive tender — common on private work and on repeat projects. Single-stage tender, pricing a fully designed scheme against drawings and specification. Or two-stage, where we are brought in earlier to work on buildability, sequencing and cost alongside the design team before the sum is fixed. On refurbishment of an existing building, the negotiated and two-stage routes tend to produce the more reliable number, because the survey and any opening-up happen before the price is fixed rather than after.

Can we keep trading during the work?

Often, depending on the scope and the layout. Where the building stays in use, work is phased so occupied areas remain accessible and compliant, with the disruptive elements scheduled outside trading hours where the programme allows. Where the building is empty, the programme is shorter and the cost is lower — if you have flexibility on timing, that is usually where the savings are.

What if the premises are leasehold?

We work alongside your surveyor or agent through the licence to alter, and we programme it as a lead item rather than a formality, because consent frequently takes longer than clients expect. Reinstatement obligations at the end of the term are worth settling before the design is fixed, since they affect what is worth installing.

What about asbestos?

On any building constructed before 2000 we arrange a refurbishment and demolition survey before intrusive work begins, and where material is present it is removed by a licensed contractor ahead of the works. It is identified at survey stage and priced into the programme rather than found once the strip-out has started.

Do you work with our architect or project manager?

Yes. We build to drawings produced by your architect and engineer and work alongside the professional team through to handover, under JCT and with the contract administrator running the process. Where a client has not yet appointed a practice, we can introduce ones we have worked with.