More specifically, how much does it cost to get planning permission for a rear extension in the UK?
This article examines the various costs you are likely to incur in developing designs for a domestic scheme up to and including applications for Listed Building Consent (in the event that you’re property is listed) and/ or for Householder Planning Consent. This type of consent is required for proposals to alter or enlarge a single house, including works within the boundary/garden of a house. It should be used for projects such as extensions, conservatories, loft conversions, dormer windows, garages, car ports and outbuildings.
In this article, to keep things simple, we’ve assumed the project in question involves a rear extension and whole house refurbishment of a typical London terraced house and that an architect is appointed to develop the design and manage the planning application.
Measured Building Survey
Before design work can begin, a measured survey of your property will need to be commissioned. Your architect should invite a number of quotes for this on your behalf to ensure good value for money.
The product of the measured survey is a set of accurate 2D drawings of your property/ site based on 3D laser scanning technology. The drawing set will typically include plans, elevations (rear, front and visible sides) and sections (vertical cuts through the building). These form the basis for architectural design work and are also required for planning where you are essentially required to show what the existing building looks like vs what you are proposing.
A 2D measured survey of a typical London Terrace will range in cost from £1,500 – £2,500 +VAT (depending on size and complexity).
For additional costs you could obtain a detailed 3D model of your property – useful when working with listed buildings with a high degree of interior detailing to be preserved. Otherwise, your architect should be able to translate the 2D survey drawings to their own 3D model as part of their workflow.
Architects’ fees will vary, based on their experience, expertise, track record, level and quality of service (read more on how to find a good archtiect here). An architects’ fees up to planning submission will be around 30%-35% of their overall project fee up to practical completion of the works.
For a typical London rear extension this would be in the range of £12,000 – £16,000 +VAT.
Structural Engineers’ Fees
A structural engineer will be required to design the structure for any extension and for any internal demolition and re-propping in order to open up areas that might be compartmentalised.
A structural engineer’s fees for the entire project, from inception to completion, could be in the range of £3,000 – £5,000 +VAT. We’ll often involve a structural engineer at Concept Design stage (RIBA work stage 2) to begin coordinating structural elements with architectural ones. Their fees at this pre planning stage may amount to somewhere in the range of £1,000 – £1,500 +VAT (within their overall fee)
The structural engineer will need to commission intrusive site & soil investigations to base their structural designs on. This may involve digging holes to establish the depth of footings/ foundations (for instance to determine whether underpinning may be required if lowering the ground/ lower ground floor to increase headroom), cutting into ceilings to establish where and what the structure is and other investigations. The cost of this is likely to be in the range of £1,000 – £1,300 +VAT.
It would be prudent to budget up to £3,000 +VAT for structural engineer and associated surveys & investigations pre planning.
Quantity Surveyor/ Cost Model
The appointment of a Quantity Surveyor (QS) is entirely optional and we’ve completed many projects successfully without a QS’s involvement. However, we have found that their involvement soon after Concept Design in the role of cost consultant can be invaluable. This could be a role that continues beyond planning and on to site, constantly keeping a check on budget, or it could be a one time sense check in the form of an Elemental Cost Model that measures every aspect of the proposed design and applies benchmark rates from comparable completed projects to create a detailed forecast of expenditure and costs.
This is often invaluable in identifying opportunities for savings early on and helps guide the design in the right direction, focusing on what’s important and avoiding the pitfalls of designs that stray from budget. A good QS will invariably save you money in the long run.
A detailed cost model prepared by a QS on the basis of Concept Design/ Stage 2 information should cost around £1,500 +VAT.
Local Authority Planning Fees
The local authority fee for Householder applications is £206. (This includes listed buildings or buildings within a conservation area)
The cost of an application for a single new build house is £462.
If your building doesn’t fall in to the above categories you can use the Planning Portal Fee Calculator to find out the cost of your application.
Additional Specialist Surveys
Depending on the location of your house and the design of the scheme, additional project specific information is sometimes required at planning stage. These could range from £200 to £2,000+ depending on the requirements and might include:
- Ecological Surveys
Flood Risk Assessment
Basement Impact Assessment
Sun and Daylight Assessment
Frequently Asked Questions
How much does pre-application advice cost?
The cost of pre-application advice varies between local authorities across the UK (in some places in the UK this advice is even offered free of charge!).
There are also differing levels of service available e.g. written advice or a meeting followed by written advice. Check with your local authority for up-to-date pre-application advice costs.
As an example, for a householder development in Westminster, the cost of a basic pre-app is £360 (inc VAT) which includes written advice within 28 days. Or a more detailed pre-app is £720 (inc VAT) which includes one meeting and written advice within 35 days
How long does planning permission take?
Normally around 8 weeks, but it could be longer depending on how large or controversial the plans are. Read our more in depth guide on How Long Does Planning Permission take here.