A Practical Guide to Fees for Extensions, Single Houses and Larger Housing Developments
So after having looked at the optimal route for planning permission in my last post I thought I would investigate costs for my own reference. In an ideal world I will figure out how to operate a design package myself – so far I am struggling to find the time to do that myself.
If you are considering a development project in the UK—whether that’s a modest extension, a one-off house, or a larger housing scheme—one of the earliest questions is usually: how much will an architect cost, and what do you get for that fee?
This article sets out realistic, UK-specific ranges for architect fees when using a standard external architectural consultancy, explains why fees vary, and clarifies whether architects normally provide Building Warrant / Building Regulations drawings.
How architects usually charge in the UK
Architect fees are normally calculated in one of three ways:
- Percentage of construction cost (most common)
- Fixed fee for a clearly defined scope (e.g. planning drawings only)
- Hourly or daily rates (typically for advice, feasibility, or very small jobs)
For residential projects, fees commonly fall somewhere between 3% and 15% of construction cost, with the percentage generally reducing as the project size increases.
A key point often missed by clients is that many appointments are not full service. Instead, work is frequently split into:
- Planning-only services, and
- Technical / Building Regulations (or Building Warrant in Scotland) services
As a rule of thumb, planning-stage work typically represents around 30–35% of a full architectural appointment, with technical design and construction-stage involvement making up the rest.
Option 1: Home extensions
Extensions are often assumed to be “simple”, but from an architect’s point of view they can be labour-intensive. Existing buildings must be surveyed, constraints worked around, and details carefully resolved—often for a relatively modest build cost.
Typical fee range
- Full service: ~8%–15% of construction cost
- Planning-only: commonly equivalent to ~2.5%–5% of construction cost
What that means in practice
- £60,000 extension → ~£5,000–£9,000 full service
- £120,000 extension → ~£10,000–£18,000 full service
Many householders choose planning-only services first, then commission technical drawings later once planning consent is secured.
Option 2: A single new house
A one-off house usually attracts a lower percentage fee than an extension, but a higher absolute cost. Fees depend heavily on how bespoke the design is and whether the architect is retained through construction.
Typical fee range
- Full service: ~7%–12% of construction cost
- Planning-only: often ~2%–4% of construction cost
Example budgets
- £300,000 house → ~£21,000–£36,000
- £500,000 house → ~£35,000–£60,000
Highly bespoke homes, complex sites, or rural locations with tighter planning controls often sit toward the upper end of the range.
Option 3: Development of around 50 houses
For larger residential developments, architect fees typically fall as a percentage, reflecting repetition of housetypes and economies of scale. However, the scope of work becomes more variable.
Key factors affecting fees include:
- Whether the architect is producing a masterplan only or full housetype designs
- The level of involvement in technical design
- Whether the architect is retained during construction
- How much work is done in-house by the developer or design-and-build contractor
Typical fee range
- ~2%–5% of total construction cost
Indicative examples
- £10 million development → ~£200,000–£500,000
- £15 million development → ~£300,000–£750,000
Some practices may quote per-unit fees or split the appointment into separate planning and technical packages.
Will an architect provide Building Regulations or Building Warrant drawings?
Yes—usually, but this is normally a separate stage of work from planning.
- In England and Wales, this means Building Regulations drawings
- In Scotland, it means Building Warrant drawings
Architects commonly:
- Prepare the detailed technical drawings
- Coordinate information from structural engineers
- Act as agent for the Building Control or Building Standards submission
However, it’s important to note:
- Structural engineering input is almost always an additional fee
- Energy, drainage, fire, or specialist compliance reports may also be required
- These consultant costs are usually not included in the architect’s headline fee
What is usually not included in architect fees?
Even with a full architectural appointment, expect additional costs for:
- Measured building surveys
- Structural engineer
- Energy / SAP / Section 6 compliance (Scotland)
- Drainage or SuDS design
- Transport, ecology, acoustics, or contamination studies (where required)
- Planning application fees and Building Warrant / Building Control fees
- VAT on professional services
A practical way to budget
When seeking quotes, it is sensible to ask architects for two clear prices:
- Planning-only service
(design development, planning drawings, and submission support) - Planning + technical / Building Regulations or Warrant service
(detailed drawings suitable for approval and construction)
This mirrors how most practices structure their work and allows you to manage risk—particularly where planning permission is not guaranteed.
Final thoughts
Architect fees are best understood not as a single number, but as a menu of services. Smaller projects tend to attract higher percentages; larger schemes benefit from economies of scale. The key is clarity: be explicit about what stages are included, what is excluded, and when further fees may arise.
If you understand that structure from the outset, architect fees become predictable, manageable, and—crucially—aligned with the level of certainty you want before committing to construction.