Finding a good architect is less about browsing portfolios and more about asking the right five questions. The best practice for your extension is the one that is properly registered, knows your borough’s planning rules, and can show real work on houses like yours.
If you are searching for architects london wide, this is how to separate a genuinely good practice from a nice looking website.
What Makes a Good Architect for a House Extension?
A good architect for a house extension is ARB registered, ideally RIBA chartered, has recent experience in your specific borough, offers a clear scope and fee, and can show completed projects on comparable homes. Registration proves they are qualified, local experience means they understand your council, and a portfolio proves they deliver.
Those four things matter more than style, because any competent architect can draw a nice extension. The hard part is getting it approved and built without surprises, and that is what the checks below test for.
Is the Architect Actually Registered?
Start here, because the title is legally protected and easy to verify.
Only someone registered with the Architects Registration Board can call themselves an architect in the UK, under the Architects Act 1997. The ARB register is public, so you can check any name in under a minute.
RIBA chartered status is a further layer. A Royal Institute of British Architects chartered practice works to an additional professional code and carries proper insurance and complaints procedures. It is not legally required, but it is a strong signal of a serious, accountable practice.
If a firm is vague about either, treat that as your answer.
Does the Architect Know Your Borough?
This is where London architects separate from each other, because planning is intensely local.
An architect who regularly works in your borough knows which streets carry Article 4 directions, where the conservation area boundaries fall, how that specific council tends to assess schemes, and what its planners expect to see. That knowledge is the difference between a first time approval and a refusal.
In Wandsworth, for example, large parts of the borough fall within conservation areas, and the council applies its own design guidance to extensions and roof alterations. A practice that has submitted applications there before understands how Wandsworth reads a scheme, which a firm parachuting in from another part of the country simply does not.
Extension Architecture is a RIBA chartered and ARB registered practice working across London and Surrey, including Wandsworth, with in house architects, planning consultants and structural engineers. That combination, local planning knowledge plus registration plus an in house technical team, is a reasonable benchmark to measure any practice against.
What Should You Ask Before You Appoint One?
Five questions tell you almost everything you need to know.
Ask for their ARB registration number, and whether they are RIBA chartered. Ask which conservation area or Article 4 position applies to your address, to test their local knowledge on the spot. Ask to see two or three completed extensions on houses similar to yours. Ask exactly what their fee covers, and what it excludes. And ask who handles the structural engineering, since that affects both coordination and cost.
Clear, confident answers mean a practice that knows its work. Hedging on registration, local rules or fees is a warning worth heeding.
How Much Do Architects Charge in London?
Architect fees for a house extension are commonly structured as a percentage of the build cost, typically in the region of 8 to 15 per cent for a full service, or as a fixed fee for a defined stage such as planning drawings.
The percentage usually falls as the project value rises, because the fixed effort of running a project does not scale in a straight line. A planning only service costs less than a full service that also covers building regulations drawings, tendering and site monitoring, so always compare like for like rather than headline numbers.
Statutory fees are separate and set nationally. The householder planning application fee in England is £548 from April 2026, and a Lawful Development Certificate is £274.
Which Architects Are Best for a Wandsworth Extension?
For a Wandsworth extension specifically, the best architect is one that already works in the borough and understands its conservation areas and local design expectations, rather than a firm that will be learning Wandsworth’s planning rules at your expense.
That local fit matters because so much of Wandsworth’s housing is period terraces and semis in or near conservation areas, where materials, proportions and roof design are scrutinised closely. Working with architects wandsworth homeowners can rely on, who know how the council assesses these schemes, is what keeps a project moving toward approval rather than stalling on a design the planners were always going to question.
The same principle applies anywhere in London. The best architect is rarely the most famous name or the cheapest quote. It is the registered, experienced practice that knows your specific area and can prove it.
The Short Answer
A good architect is easy to verify and hard to fake. Registration is a public record, borough experience shows up the moment you ask about your own street, and a portfolio either exists or it does not.
The firms worth your money are the ones that answer all of it without flinching.
