If you are looking to understand Architects costs for an extension or Chartered Architectural Technologist for a house extension, home extension, loft conversion, or new build, this complete guide to architect fees covers everything you need to know from how architects structure their fees and typical architect fees for an extension, through to planning permission, building regulations, and all the costs to consider across the UK.
How Much Do Architects costs for an extension?
Find out how much architects cost to hire and you will quickly discover that fees vary enormously. Architect fees for a house extension in the UK typically fall between £1,800 and £8,000+ depending on scope, location, and complexity of the project.
What are alternatives to Architects
Chartered architectural technologist, so what is that? Architectural technologist is a technical professional who specialises on the technical side, for example Building regulation drawings, they look at value engineering element, providing a better performance of a building not just aesthetics. Better performance means cheaper energy bills. As things are getting more and more expensive it best to go for a technical professional who can vastly improve your building performance.
Unlike architects, technologists tend to concentrate more on how a building is constructed rather than what it looks like. They develop detailed technical specifications covering elements such as the building fabric, insulation, waterproofing, structural systems, and overall performance. On smaller residential projects, they often take on a leading role handling planning applications, coordinating with engineers, and providing guidance on site feasibility.
Architectural technologist can do a complete architectural services from conception to through to completion and project management.
How AC Design Solution Can Help You
AC Design Solution is a CIAT-accredited multi-disciplinary practice Covering architectural technology, structural engineering, party wall, planning application, building regulations. We are local architectural technologists with direct experience across Westminster, RBKC, Hounslow, Harrow, Ealing, Hammersmith and Fulham, Brent, Wandsworth, Islington, and beyond. Our fees are always fixed fees not percentages fees, this is to help save the client costs and get the job moving.
How do AC Design Solution price an extension?
We have years of experience and have covered almost every scenario. We understand that an extension in a borough like Brent and a borough like Westminster can vary substantially. This is because planning policy is tighter in certain areas, more reports are required, and the houses have more detailing within them for example external cornices, splayed windows, and stone detailing. We study the house first, research what reports are required, look at the property from multiple sources rather than just Google Maps, review previous applications and appeals, and then provide a fixed fee covering all reports.
So how can we offer all this when other architects want to stage their work? The simple answer is that we have a team not just Chartered Architectural Technologists, but Chartered Civil Engineers for flood risk assessments, structural engineers for basement impact assessments where an extension reaches basement level, and surveyors to provide heritage reports.
We understand that clients want to get through planning and start the build. Our process makes that considerably easier.
We are aware that some architects will read this and say it is not fair, that practices like ours drive down the price. That is not true. We have over ten years of physical experience in construction and twelve years of drawing experience. We know our worth. Fixed fees work better for both us and the client. We turn projects around quicker with the exact same level of detail as other architects, if not more. Our packages are all BIM modelled and clash detected, and our site measurements are not a simple laser measure — we scan your property.
How Do Architects Structure Their Fees?
Understanding how architects structure their fees is essential if you want to budget accurately and compare quotes with confidence. In the UK, most architects use one of four common pricing models. Knowing how each works will help you choose the right option for your home extension or residential project.
Percentage Fee
One of the most common approaches is a percentage of the construction cost. For residential projects, this typically ranges from 5% to 15%.
For example, if your build cost is £100,000, architect fees could fall between £5,000 and £15,000.
While this method is straightforward, it means fees increase as construction costs rise — not necessarily in line with the amount of work involved. Architects costs for an extension this can make percentage-based pricing less cost-effective compared to fixed fees.
Fixed Project Fee
A fixed fee is agreed upfront for a clearly defined scope of work. This is often the most transparent and predictable option, making it a popular choice for residential projects.
With a fixed fee:
- You know your costs from the outset
- Individual services can be clearly itemised
- There are no unexpected increases as the project progresses
This approach is particularly well-suited to standard home extensions and renovations.
Hourly Rates
Architects may charge hourly rates when the scope of work is uncertain. In the UK, rates typically range from £60 to £175 per hour, depending on experience and location.
This pricing model is commonly used for:
- Feasibility studies
- Initial consultations
- Dispute resolution
- Project rescue work
If you agree to hourly billing, it’s important to request a time estimate upfront to avoid unexpected costs.
Stage-Based Fees
For larger or more complex projects, architects often charge based on project stages. These stages usually follow the framework set out by the Royal Institute of British Architects.
Each stage from concept design through to technical design and construction — is priced and invoiced separately. This allows you to:
- Maintain control over spending
- Pay in line with project progress
- Make informed decisions at key milestones
However, costs can vary at each stage depending on the complexity of the design and any changes made along the way.
Do Architectural Technologists Charge Differently?
Professionals accredited by the Chartered Institute of Architectural Technologists generally use the same fee structures as architects including fixed fees, percentages, hourly rates, and stage-based pricing.
The main difference is often cost and approach. Architectural technologists typically focus more on the technical delivery of a project, which can make them a more cost-effective option for straightforward residential work such as extensions and refurbishments, this is why many are now more in business than your regular architect, who try to charge per stage.
Architect Fees for an Extension — What Affects the Cost?
Complexity of the Project
A good architect will identify early on what level of complexity your project involves. How much architects charge for a home extension rises in line with complexity — structural glazing, cantilevered elements, or bespoke joinery all increase the work an architect will charge for on any residential project. Extension costs UK-wide follow this pattern consistently, and fees are affected by complexity more than any other single factor.
Planning Permission and Building Regulations
Whether your house extension requires planning permission directly affects architect fees. A planning application adds professional time for drawings, planning statement preparation, and liaison with the Local Planning Authority during determination.
Building regulations approval is legally required for all structural works regardless of planning permission — it sets minimum standards for structural integrity, fire safety, insulation, and drainage.
Extension in London vs Costs UK-Wide
An extension in London for example single storey extension attracts higher fees than the same project elsewhere in the UK. Local architects in London face higher overheads and Local Planning Authorities — particularly Westminster, RBKC, and Islington — require a higher standard of documentation to grant planning permission. When you calculate the cost of a home extension project, location is one of the most significant variables affecting what architects charge across the UK.
How Much Do Architects Charge for a Home Extension?
How much do architects charge for a single storey rear extension in London? For a complete service covering drawings, planning application or permitted development, and building regulations, architect fees for an extension typically fall between £2,000 and £3,500 excluding VAT. Outside London, costs UK-wide for the same scope are generally £1,500 to £2,800.
For a double storey house extension requiring a full planning application and complete building regulations package, expect to charge for an extension at £3,000 to £5,000. The fee reflects greater structural complexity and a more detailed building regulations submission. For a listed building, fees may start at £4,000 and reach considerably more depending on the extent of works.
Architects May Charge More in These Circumstances
Architects may charge significantly above typical fees for the following project types. Understanding where fees may be higher helps you budget accurately for your residential project before requesting architect quotes.
- Listed buildings — architects may charge £4,000 to £15,000+ requiring heritage justification and specialist drawings alongside the planning application
- Conservation area extensions — architects may charge more in boroughs such as Westminster or RBKC where pre-application engagement and heritage assessments are required before a planning application can be submitted
- Complex building regulations requirements — fire strategy, acoustic design, SAP calculations, and Part M access compliance add to the building regulations submission and mean architects may charge a higher fee on affected residential projects
- New build schemes — architect fees for a new build are higher, reflecting the full scope from planning application through to building regulations sign-off
Architect Cost Calculator — Calculate the Cost
Although we are not architects and are Chartered Architectural Technologists you can use our free quick quote to obtain a cost.
Costs to Consider Beyond Architect Fees
When you pay for architect fees you are not covering every professional cost associated with a home extension. These additional costs sit alongside architectural fees and must be factored into your total budget from the outset.
| Cost Item | Typical Amount (excl. VAT) |
|---|---|
| Planning application fee (householder) | £548 as of April 2026 |
| Building control (Full Plans) | £500 – £1,500 |
| Party wall surveyor | £700 – £2,500 per neighbour |
| Measured building survey | £400 – £1,200 |
| Heritage or archaeological report | £800 – £3,000 |
| Flood Risk Assessment | £400 – £900 |
| SAP energy assessment | £200 – £500 |
What Do Architects Offer on a Home Extension?
Architects and Chartered Architectural Technologists offer a full service on a typical home extension: feasibility and site appraisal; concept and developed design; planning application preparation and submission; building regulations Full Plans submission; structural engineering coordination; specification of materials; and construction-stage support. An architect can help you navigate planning policy, building regulations, and contractor management in ways that an unqualified designer simply cannot.
At AC Design Solution, our multi-disciplinary in-house team means all of these services are coordinated under one roof, so the planning application, building regulations package, and structural drawings are produced as a single coherent set — not reconciled from separate consultants after the fact.
Hidden Costs of Online Architects
Online architects frequently exclude building regulations, structural engineering, and construction support from their headline fee. When you add these individual costs back in, the total cost to hire an architect through an online service often exceeds what a good architect based locally would have charged. An experienced architect based in your area will know your Local Planning Authority’s policies, attend site, and provide a coordinated service that online architects simply cannot match. Always check what is included before you pay for architect fees from any online provider.
How to Cut Costs Without Cutting Corners
There are legitimate ways to cut costs on professional fees without compromising your home extension project:
- Use permitted development where possible — avoiding a planning application cuts costs on both the application fee and professional time
- Choose a multi-disciplinary practice — paying individual costs to separate firms for architectural, structural, and party wall work almost always costs more than a single coordinated practice covering all three
Do You Need an Architect? Registered vs Unregistered Designers
An architect must be registered with the Architects Registration Board to use the title ‘architect’ in the UK. A Chartered Architectural Technologist must hold MCIAT designation from CIAT. Both registers are publicly searchable online. Unregistered designers carry no professional indemnity obligation and no code of conduct. For any home extension involving structural work, a planning application, or building regulations approval, always instruct a professional registered with the Architects Registration Board or CIAT.
