Quick summary: cost of house extension plans
The cost of house extension plans will usually depend on whether you need simple planning drawings, a more detailed Building Regulations package, or a complete set covering both stages. For a straightforward UK house extension, homeowners might typically budget around £700–£1,500 for planning-stage drawings, while a fuller planning and technical drawing service can often reach £1,500–£3,000+.
- Measured survey and existing drawings: commonly around £300–£700, depending on the property.
- Planning drawings for a typical extension: often around £700–£1,500.
- Building Regulations / technical drawings: commonly around £800–£1,800+, depending on complexity.
- Combined drawing packages: frequently around £1,500–£3,000+, with complex or architect-led projects potentially costing more.
These figures are guide ranges rather than fixed UK fees. Structural calculations, planning application charges, Building Control fees, specialist reports and professional advice may all be charged separately.
Trying to budget for your extension drawings?
Tell us what you are hoping to build and we can explain which drawings you are likely to need before you start paying for unnecessary work.
Cost of house extension plans: typical UK price ranges
There is no single national fee for preparing extension plans. The price depends on the size of your home, the type of extension, the amount of design work involved and, importantly, exactly what the quoted service includes.
As a broad homeowner guide, a relatively straightforward planning drawing package may fall around £700–£1,500. However, if you also require detailed technical drawings for Building Regulations, the total professional drawing cost could move towards £1,500–£3,000+.
Quick costs snapshot for extension plans
- Measured survey: approximately £300–£700.
- Planning-stage plans: approximately £700–£1,500.
- Technical / Building Regulations drawings: approximately £800–£1,800+.
- Combined planning and technical package: often £1,500–£3,000+.
- Complex or highly bespoke extensions: professional fees may exceed these ranges.
VAT, structural engineering, planning application charges, Building Control charges, drainage advice and specialist reports may be additional.
The figures above should also be viewed alongside your wider construction budget. If you are still working out what the complete project could cost, our complete homeowner guide to extension budgeting explains the much larger build-cost picture.
What is included in the price of house extension plans?
One of the easiest mistakes is comparing two quotations simply by looking at the final figure. One company may be offering a basic planning package, while another may include surveys, revisions, application management and technical construction information.
Planning-stage extension drawings
A typical planning package may include:
- existing floor plans;
- proposed floor plans;
- existing and proposed elevations;
- a roof plan where required;
- a site or block plan;
- a location plan; and
- sections or additional drawings where the design needs them.
Our guide to what extension drawings normally contain explains these documents in more detail.
Measured survey costs
Before accurate drawings can be prepared, somebody normally needs reliable dimensions of the existing property. A measured survey may be included in the quotation or listed separately.
Larger homes, complicated roof shapes and properties with difficult access generally take longer to survey. Therefore, they can push the overall drawing fee upwards.
Planning extension plans vs Building Regulations plans
Planning and Building Regulations are separate parts of the project, and the drawings used for each stage serve different purposes.
Planning drawings
Planning drawings concentrate mainly on the size, position, appearance and relationship of your extension to the existing property and neighbouring homes.
Depending on the proposal, you may need full planning permission. Alternatively, the work may fall within permitted development rights if all relevant conditions are satisfied. You can read our homeowner guide to checking permission for an extension for a fuller explanation.
Building Regulations drawings
Technical drawings go further. They may show insulation, foundations, wall construction, roof build-ups, ventilation, drainage, fire precautions and other information needed to demonstrate compliance with the Building Regulations.
Because this stage involves more construction detail, it can increase the total cost substantially. Our guide to the drawings normally prepared for Building Regulations explains what homeowners should expect.
Not sure which level of plans your extension needs?
We can look at your proposal and explain whether you need planning drawings, Building Regulations drawings, or both.
What affects the cost of extension plans?
House extension plans cost more when the designer has to spend more time surveying, designing, revising or coordinating the project. Several factors can therefore change the quotation.
Size and complexity
A simple rectangular rear extension is normally quicker to draw than a wraparound extension, split-level design or project involving substantial changes to the existing house.
Single-storey vs two-storey extensions
Two-storey extensions generally involve more elevations, more design considerations and additional structural coordination. Consequently, drawing fees are often higher.
Number of revisions
Some companies include one or two rounds of amendments, while others charge separately once an agreed allowance has been used.
Planning complexity
A house in a conservation area, a property with restricted permitted development rights or a proposal close to neighbouring properties may require more careful design work.
Technical coordination
Structural calculations are commonly prepared separately by a structural engineer. However, the extension drawings still need to coordinate with beam sizes, openings and other structural requirements.
You can see why this matters in our guide to when structural calculations are required.
How much does an architect cost for extension plans?
An architect-led service can cost more than a straightforward drawing service because the appointment may include greater design input, option development, specification work and assistance during construction.
However, homeowners do not have to use an architect simply to prepare every domestic extension plan. Depending on your project, drawings may also be prepared by an architectural technologist, technician or another suitably experienced building design professional.
Therefore, compare the scope of service, not simply the professional title. Our guide to choosing professional help for planning drawings explains the differences in more detail.
How to compare the cost of house extension plans
A sensible comparison should answer more than “which quote is cheapest?”. Instead, check whether each provider is pricing the same work.
Step-by-step extension plan quote checklist
- Define your extension. Decide whether it is rear, side, wraparound, single-storey or two-storey.
- Confirm whether a measured survey is included. Do not assume it is part of the advertised drawing price.
- Check the planning scope. Ask exactly which plans and elevations will be supplied.
- Ask about revisions. Find out how many design changes are included.
- Check whether submission is included. Preparing drawings and managing the planning application are not always the same service.
- Separate technical drawings from planning drawings. Confirm the price of the Building Regulations stage.
- List third-party costs. Structural engineering, drainage work and specialist reports may sit outside the drawing fee.
- Compare the complete service. Choose the package that fits the project rather than simply the lowest headline price.
House extension plan prices compared
Search results often mix together several different questions: the price of drawings, the price of planning permission and the actual cost of building an extension. They are separate expenses.
- Extension plans: professional fees for surveys, design and drawings.
- Planning costs: application charges and any professional application-management fees.
- Building Regulations costs: technical design work plus Building Control charges.
- Construction costs: labour, materials, groundwork, finishes and contractor overheads.
For the construction side of the budget, see our guide to the overall price of building a house extension.
Will your local council affect the price?
It can. Local planning authorities work within national planning legislation, but local policies, conservation designations and validation requirements can affect the information needed for an application.
In addition, permitted development rights can be restricted in particular circumstances. Therefore, homeowners should not assume that an extension which was acceptable elsewhere will automatically follow the same route at their own property.
FAQs: cost of house extension plans
How much do house extension plans cost in the UK?
For a straightforward home extension, planning-stage drawings might typically fall around £700–£1,500. A more complete package including technical Building Regulations drawings could move towards £1,500–£3,000 or more. Complex properties and extensive design work can cost more.
How much does drawing up house extension plans cost?
The answer depends on what “drawing up plans” includes. A basic planning package is normally cheaper than a service that also includes a measured survey, several design options, application management and technical construction drawings.
How much does planning cost for an extension?
Planning costs are separate from the cost of preparing drawings. Depending on your project, you may have a local authority application fee as well as professional fees for drawings, planning advice or managing the submission.
How much does an architect cost for extension plans?
There is no fixed architect fee. Prices vary according to the size of the extension and whether you want concept design, planning work, technical design and assistance during construction. For that reason, compare the written scope as well as the headline fee.
Do I need planning drawings if my extension is permitted development?
You may still need accurate drawings even where full planning permission is not required. Drawings can be useful for checking compliance with permitted development limits, obtaining a Lawful Development Certificate, preparing technical information and helping your builder understand the work.
Are extension plans priced per square metre?
Professional drawing services are not normally priced in exactly the same way as construction work. The designer's workload depends on survey time, complexity, design development and the number of drawings required, so two extensions with similar floor areas can attract different fees.
Have a quote and want to know what it actually includes?
Our team can help you understand the drawings and approval stages your project is likely to need.
Next steps & useful guides
If you are working out your extension budget, these related Plans Made Easy guides can help you understand the next stages:
- Extension budgeting from design through to construction
- What drawings are normally required for an extension
- Checking whether your proposal needs planning permission
- Understanding the technical drawing stage
- When a structural engineer may be needed
- Choosing who should prepare your drawings
- Budgeting for the complete build
- Planning drawings Approximately £700–£1,500 for many straightforward domestic extensions.
- Technical drawings Building Regulations drawing packages can commonly add around £800–£1,800+.
- Combined package A fuller planning and technical service may commonly reach £1,500–£3,000+.
- Biggest price factors Property complexity, extension size, design work, survey requirements, revisions and level of technical detail.
- Common extras Structural calculations, application fees, Building Control charges and specialist reports.
- Best comparison method Compare exactly what each quotation includes rather than choosing on headline price alone.
Planning an extension? Ask Plans Made Easy what drawing stages your project is likely to need.
Official guidance and useful external resources
Planning rules and construction costs change over time, so it is sensible to check current information before committing to a project.
- GOV.UK guidance on when planning permission may be required
- Planning Portal guidance on extensions and permitted development
- Office for National Statistics construction output price data
- Royal Institute of British Architects guidance on working with an architect
How to budget sensibly for your extension plans
The cheapest set of plans is not necessarily the cheapest route through an extension project. What matters is whether the drawings are accurate, suitable for the approval stage and detailed enough for the people who need to use them.
Therefore, start by establishing whether your project needs planning permission, permitted development confirmation, Building Regulations approval or a combination of these. Then obtain a quotation that clearly identifies the survey, drawings, revisions and submission work included.
Plans Made Easy helps homeowners work through those stages in a practical order, so you know what you are paying for and why before the project progresses.
Ready to move your extension project forward?
Plans Made Easy can prepare compliant plans, manage submissions, and guide you from idea to approval.
Performance Verified ✅
This page meets PME Optimisation Standards — achieving 95+ Desktop and 85+ Mobile PageSpeed benchmarks. Verified on
