How much do architectural drawings cost for a home extension?
It’s one of the most common questions homeowners ask when they start thinking about an extension — and one of the least straightforwardly answered on most architectural websites. Costs vary. It depends on the project. Get in touch for a quote. All of which is true, but none of which actually helps you understand what you’re likely to be spending before you pick up the phone.
So here is a straight answer, along with the context that makes it useful.
What architectural drawings actually cover
Before getting to numbers, it’s worth being clear about what you’re paying for — because architectural drawings aren’t a single thing. A residential extension project typically involves two distinct sets of drawings, produced at different stages, for different purposes.
Planning drawings are the first set. These are the drawings submitted to your local planning authority as part of a householder planning application or lawful development certificate application. Their job is to show what is being proposed — the size, appearance, and layout of the extension — clearly enough for a planning officer to make a decision. They include a site location plan, existing and proposed floor plans, and existing and proposed elevations.
Building regulation drawings come second, after planning is resolved. These are the detailed technical documents that show how the extension will actually be built — structure, insulation, drainage, ventilation, foundations, and all the other elements that building regulations require to be addressed before construction can begin. Where planning drawings communicate intent to a planning officer, building regulation drawings communicate method to a builder and a building control inspector.
Both sets are essential. One without the other doesn’t get a project built.
What do architectural drawings cost?
For a typical residential extension project with jakeunderwood.com, planning drawings are priced from £1,350 plus VAT. Building regulation drawings are priced from £1,200 plus VAT. Both fees are confirmed in a written quote before any work begins, and the quote is specific to your project — so what you’re told at the outset is what you pay. No hidden costs, no surprises at invoice stage.
The payment structure is straightforward. The first payment falls due after the measured survey of your property is completed — the stage at which accurate base drawings of the existing house are produced and the design work begins. The second payment falls due after planning approval is granted, when the project moves into the building regulation drawing stage. Payments are tied to project milestones rather than arbitrary dates, which means you’re paying for work that has been completed and for progress that has been made.
Fees vary with the size and complexity of the project — a straightforward single-storey rear extension has a different scope to a two-storey side and rear wraparound with a loft conversion above — and the quote reflects that. But the principle is consistent: clear fees, confirmed upfront, with no ambiguity about what’s included.
What else do you need to budget for?
Architectural drawing fees are one part of the total professional fees picture, and understanding the full cost landscape from the outset avoids the kind of surprises that derail project budgets.
The planning application fee is paid directly to the local planning authority and is set nationally. For a householder application it is currently £548. This is subject to change, so it’s worth confirming the current figure at the time of application.
Building control fees are paid to the building control body — either the local authority or an approved private inspector — and cover the plan checking and site inspection service throughout the build. Fees vary depending on the size and value of the works, but for a typical single-storey rear extension they sit in the region of £500 to £900.
A structural engineer will be needed for most extension projects to design the steelwork or timber structure and to produce the calculations that building control requires. Structural engineering fees for a straightforward extension typically start from around £500 to £800, rising with complexity.
Where an extension is within three metres of a neighbouring property’s foundation — which applies to the majority of terraced and semi-detached houses — a party wall agreement may be required under the Party Wall etc. Act 1996. Party wall surveyor fees vary depending on whether the neighbour appoints their own surveyor, but budgeting £800 to £1,500 for a straightforward party wall matter is sensible.
Taken together, the full professional fees picture for a typical single-storey rear extension — architectural drawings, planning fee, building control, structural engineer, and party wall where applicable — sits broadly in the range of £4,000 to £6,000 depending on the specific project and the route taken. That figure sits alongside the build cost, which for a single-storey rear extension in Surrey typically starts from around £2,000 to £2,500 per square metre.
Why clear fees matter
The professional fees stage is where trust is established — or not. A homeowner committing to an extension project is making one of the most significant financial decisions of their family’s life. Vague fee structures, costs that emerge gradually as the project develops, and invoices that don’t match what was discussed at the outset all erode the confidence needed to make that commitment.
At jakeunderwood.com, every project starts with a written quote that sets out exactly what’s included and what it costs. That quote is prepared specifically for your project — not taken from a standard rate card — so that it reflects the actual scope of work involved. If anything changes during the project that affects the fee, that conversation happens before the work is done, not after.
It’s a straightforward way of working. Based on what clients tell us, it’s less common than it should be.
FAQ
Are architectural drawing fees the same regardless of which designer I use?
No — fees vary significantly between practices depending on their size, overhead, and the level of service included. The most useful comparison isn’t the headline fee but what’s included in it: how many design iterations are covered, whether the planning application is managed on your behalf, whether building regulation drawings include structural coordination, and how accessible the designer is throughout the process. A lower fee that excludes half the service isn’t necessarily better value.
Do I pay for architectural drawings even if planning permission is refused?
The planning drawing fee covers the work of producing the drawings and managing the application — not the outcome of the planning decision. If a planning application is refused, the drawings have still been produced and the application has still been managed. However, we work hard to avoid refusals by understanding the planning context before the design is developed and shaping the proposals accordingly. In the event that a revised application is needed, we discuss the implications for fees openly before any further work is undertaken.
What’s included in the measured survey?
The measured survey involves visiting the property and taking detailed measurements of the existing house — room by room, inside and out — to produce accurate base drawings of the existing floor plans and elevations. These base drawings are what the design proposals are built on, and their accuracy is what ensures that the planning drawings and building regulation drawings reflect the actual property rather than an approximation of it. The survey visit is included within the overall project fee.
Want to know what your project would cost?
Every project is different, which is why we prepare a specific written quote for each one — so you know exactly what to expect before any work begins. We work with homeowners across Surrey, Hampshire, Berkshire, and London, and the quote conversation is always free and without obligation.
Get in touch at jakeunderwood.com or call 07784 927778 to find out what your project would involve and what it would cost.
