Frequently Asked Questions About Home Renovation, Retrofit, and Architecture

Our fees vary depending on the project’s scope, complexity, and the level of service you need. Every project begins with our Architect’s Home Visit and Appraisal, which gives you early clarity on what’s possible, what it might cost, and what route makes the most sense for you.

From there, we use a range of fee structures depending on the stage and nature of the work.
When the scope is well defined, we’ll usually offer a fixed fee — this gives you cost certainty and peace of mind from the outset.
In the early stages, or when the scope is still evolving, a time-based or percentage fee may be more appropriate. This ensures you only pay for the work that’s actually needed as the project takes shape.

Each approach has its strengths:

• Fixed fees provide clarity and help with budgeting.

• Time-based fees offer flexibility when the brief or design is still fluid.

• Percentage fees can fairly reflect the scale of work when costs are not yet known.

We’ll always explain which model best suits your situation before you commit — so you can make an informed choice with confidence.

The cost of construction depends on many factors — the property’s location, condition, access, and the quality of materials and finishes. In London, prices have risen in recent years due to labour shortages and inflation, so getting an accurate early forecast is more important than ever.

As a broad guide for 2025:

• Single-storey extension: £2,500 – £4,000 per m²
  Finishes, glazing, and structural complexity have the biggest impact.

• Two-storey extension: £2,000 – £3,200 per m²
  Economies across both floors reduce average cost.

• Basement work: £4,500 – £6,000 per m²
  Higher due to excavation, waterproofing, and risk.

• Full-house retrofit or refurbishment: £1,800 – £3,800 per m²
  Varies with energy-performance targets and extent of reconfiguration.

• Kitchens and bathrooms: from £15,000 – £40,000+
  Quality of fixtures, fittings, and bespoke joinery affects cost.

These figures exclude VAT and professional fees.

The size and specification of your project have the greatest impact on cost, so we use area-based benchmarks early in design to set a realistic budget.

Every project begins with our Architect’s Home Visit and Appraisal, which includes a tailored construction cost forecast and full project budget assessment before you commit to detailed design. As the design evolves, we continuously test it against live market data to keep the project financially viable from start to finish.

Alongside the construction cost itself, you’ll need to allow for statutory fees, professional consultants, and other related expenses.

As a broad guide, professional and statutory costs typically add around 15–25% on top of the construction cost. These may include:

• Architect and design consultant fees – including structural engineer, mechanical or electrical designer, and landscape designer.

• Principal Designer (Building Regulations) role – a new requirement under the Building Safety Act, ensuring that safety and compliance are considered throughout design.

• CDM (Health and Safety) Principal Designer or Client Advisor – separate from the Building Regulations role, this covers health and safety duties under construction law.

• Planning application and Listed Building Consent fees – payable to your local authority.

• Building Control fees – for plan checks, inspections, and final certification.

• Party wall surveyor fees – if your project affects a shared boundary.

• Insurance and warranties – including home insurance during works or optional build warranties for added protection.

• VAT – usually applicable to both construction and professional fees for work to existing properties.

We’ll outline these costs clearly at the start of your project and keep them updated as your design progresses. Our Architect’s Home Visit and Appraisal includes an early budget overview, so you can plan with confidence from day one.

We prepare a construction cost forecast and a whole-project budget plan before design begins, as part of our Architect’s Home Visit and Appraisal. This gives you a clear understanding of what your ambitions are likely to cost — including construction, professional and statutory fees, VAT, contingencies, and risk.

Rather than relying on generic £/m² rates, we build a scope-specific forecast based on your home, brief, and site constraints. We may reference costs from recently completed projects for context, but every project and every client is different, so the forecast is tailored to you.

As the design develops, we update the forecast at each stage, testing options and refining assumptions. This helps you make informed decisions about priorities, quality, and timing — ensuring your investment delivers the best value for you.

During construction, we administer the building contract, review valuations, manage variations, and maintain a clear cost record so you always know where things stand.

Our proposals set out the scope of services, deliverables, and fee structure for each stage of the project. We outline the likely activities, key milestones, and any allowances for surveys or specialist consultants, so you have a clear understanding of what’s included from the outset.

At the early stages, there are still many variables — project scope, planning complexity, and technical requirements may change — so it’s not always possible to give a fixed fee straight away. Instead, our proposals explain how fees will be calculated and adjusted as the project becomes more defined.

All of our appointments are governed by the RIBA Domestic Professional Services Contract, which clearly sets out roles, responsibilities, and payment terms. This ensures transparency and accountability at every stage, so you know exactly what to expect as your project progresses.