Architect or design and build: who first?

Two routes that look similar and are not

An architect first means you appoint a designer who works for you and then ask builders to price the drawings, while design and build puts design and construction in one contract with one firm.

Which? describes design and build as one firm managing both the design and the construction under a single contract, and says this can be simpler than coordinating separate professionals. The architect route splits the job. You appoint the designer, agree the drawings, and then invite builders to price them. The two routes can end with the same brick extension on the back of the same Rugby house. What differs is who holds the pen, who is paid for what, and who you complain to when something does not fit.

The same Which? guide adds a third option that people forget: a good builder alone. It says a builder can often handle an extension, especially a kitchen extension or a loft conversion, and suggests considering an architect for larger work such as reconfiguring the house or adding a double storey extension. That matters because many homeowners assume the choice is a dramatic one between a famous name and a cowboy. For a plain rear extension, the honest answer is often a calm conversation about scope.

Check the guidance: Which?: advice from a builder and an architect (published 2 March 2026), Fifi McGee: do I need an architect for an extension?.

What the word architect legally means

No law requires you to use an architect for an extension, but only someone on the Architects Registration Board register may call themselves one professionally.

The Architects Registration Board says that in the UK a person must be on its Register of Architects to call themselves an architect professionally, and that using the title without being registered is a criminal offence. It adds that registered architects must hold appropriate qualifications, keep their skills up to date, follow the Architects Code and carry insurance. You can check anyone for yourself on the register at architects-register.org.uk, which takes a minute and costs nothing.

Build It magazine makes the other half of the point. There is no legal requirement to use an architect, and anyone can call themselves a designer. An architectural designer or technologist may be perfectly capable of drawing a straightforward extension, and some are excellent, but the title tells you less about their training and regulation. Build It also notes that architects complete seven years of training, five of study and two of practical experience, and that some also choose to become chartered members of RIBA. Treat the word designer as a prompt to ask for a portfolio and for references from domestic extension clients, not as a warning sign.

None of this tells you a particular architect is better value than a particular designer. It tells you what you can verify. If a firm describes someone as an architect, check the register. If it describes someone as a designer, ask about their qualifications, their insurance and who checks their drawings before they go to the council.

Check the guidance: Architects Registration Board: public information, Build It: who should design my extension?.

Where each route meets Rugby planning and building control

Whoever draws the extension, the Rugby planning and building control checks are the same, and they are separate from each other.

Rugby Borough Council's planning page explains that permitted development rights let you make some changes without planning permission, that those rights can be adapted or removed, and that they can differ for listed buildings and properties in conservation areas. It also says building regulations approval may be needed whether or not planning permission is. In other words, the design has to clear two separate checks, and a drawing that suits one can fail the other.

The table below shows how the routes line up against those checks. It is an original comparison for decision making, not a price list, and the right-hand column is a set of questions rather than answers.

Check the guidance: Rugby Borough Council: do I need planning permission?, Rugby Borough Council: help with your planning application, Rugby Borough Council: Warwick Building Control, Warwick District Council: making a building regulations application, Planning Portal: full plans application.

When an architect first makes the most sense

The case for an architect first is strongest when the design is complex, the brief is unclear, or the house is listed or in a conservation area.

Which? says an architect offers more project support and often a more considered finish, particularly on complex projects or where the brief is unclear. Build It quotes a chartered building surveyor saying that as the complexity of the extension rises, so does the need for qualified architectural input. Both are sensible reasons, and both are conditions you can test against your own house rather than a sales pitch.

Rugby has 19 conservation areas, and the council says it has extra powers to control development in them and asks householders to speak to its development control team before starting any work. If your house sits in one, an architect who has dealt with the character appraisal for that area is a practical asset. Build It makes the same recommendation for listed buildings and conservation areas, suggesting an architect with heritage experience. Read the appraisal for your area before you brief anyone, because it shapes what the council is likely to accept.

Check the guidance: Which?: advice from a builder and an architect (published 2 March 2026), Build It: who should design my extension?, Rugby Borough Council: conservation areas and character appraisals, Fifi McGee: do I need an architect for an extension?.

When design and build can suit a simple Rugby extension

Design and build tends to suit a well defined, conventional extension where you want one contract, one point of contact and a single firm answerable for design and construction.

A rear extension with a conventional layout, a clear idea of how it connects to the kitchen and no heritage constraints is the kind of job where one firm handling design and construction can reduce friction. Which? says this can be simpler than coordinating separate professionals. There is no need for the builder to interpret someone else's drawings, because the same firm drew them. That can mean fewer finger pointing moments when a detail does not work on site.

The trade off sits in the same place as the benefit. Because the designer works inside the builder's company, the design is shaped by what that firm likes to build, and the usual market checks are weaker. With an architect's drawings you can ask two or three builders to price the same scheme and compare them line by line. With design and build you have one price for one design, so you must work harder to test it. Ask for a written scope that lists what is and is not included, and ask what happens if you want a different builder after the design is done.

Check the guidance: Which?: advice from a builder and an architect (published 2 March 2026).

What the sources say about fees, and what they do not

Which? says architect fees are usually around 15 per cent, one architect's blog says 8 to 12 per cent without a source, and no source opened gives a verified Rugby fee.

The two fee figures do not agree, and neither is a quotation. Which? says architect fees are usually around 15 per cent of the project and tells readers to budget for it. The Fifi McGee blog gives around 8 to 12 per cent of the project fee, with no source for the figure. Both are percentages of a build cost you do not yet know, so they are a way to frame a conversation, not a budget line. Do not plan a Rugby budget around either number.

The sources opened for this guide do not give a verified Rugby fee for an architectural designer or for a design and build service, so this guide does not offer one. Search results showed several directory pages with cost ranges, but those pages were not opened or could not be opened, and a search snippet is not evidence. Anyone quoting you a fee should state in writing what stages it covers, whether VAT is included, and what extra work is charged separately.

Check the guidance: Which?: advice from a builder and an architect (published 2 March 2026), Fifi McGee: do I need an architect for an extension?.

Questions to put to anyone before you sign

The best protection is a written scope that says who designs, who submits, who owns the drawings and who pays when the design changes.

Use the same questions with an architect, a designer or a design and build firm. The answers matter more than the label on the contract, and a firm that answers clearly in writing is easier to work with than one that reassures you in conversation.

• Who is the designer, what are their qualifications, and can I check them on the ARB register or with their professional body?
• Which stages does the fee cover, and what is charged separately, such as structural calculations, surveys, planning fees and building control fees?
• Who submits the planning application and the building regulations application, and who deals with the council's questions?
• Do I own the drawings if I part company, and can another builder price them?
• How are design changes handled during the build, and who pays for them?
• When does the price become fixed, what is provisional, and what happens if the ground, a drain or a structural check changes the design?
• Can I see a domestic extension in a similar Rugby house type, and can I speak to the client?

Check the guidance: Which?: advice from a builder and an architect (published 2 March 2026), Architects Registration Board: public information.

Which? also advises avoiding a choice made on price alone and never paying in cash. Build costs and design fees are separate lines, so compare them separately.

Bottom line: Choose the route that matches the complexity of your house and brief, then get the scope, the responsibilities and the price in writing before you commit.