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In the ever changing world of real estate, understanding the financial side of home renovations is becoming more and more important for homeowners. With rising property values and the desire for more space many are looking at house extensions as an option. But without proper budgeting and knowledge of costs planning such a project can get overwhelming.
In 2024 several factors will impact the cost of house extensions including the type of extension, location and design. Single storey extensions, double storey extensions and conservatories are the most popular options and each vary greatly in price and function. Knowing these different types and their costs is key to making informed decisions.
This article will explain the costs of house extensions in 2024, the factors that impact pricing and the extra costs. By breaking down the stages of a house extension project and providing budgeting tools homeowners can navigate the process of creating their dream home.
Budgeting is key when planning a house extension. The project cost is calculated by total internal floor area in square metres and multiplying it by the average cost per square metre which in the UK is between £1,500 and £2,500. Beyond the basic construction costs there are extra costs to consider such as professional services like architectural fees and planning permissions. The planning application fee is £206 and even if planning permission is not required it’s always worth getting a Lawful Development Certificate for compliance.
To get a realistic budget for your house extension get quotes from multiple contractors. The type of extension – single storey rear, kitchen, bathroom, conservatory or multi level extension and the materials used will impact the final cost. Quality of finish and compliance with building regulations will also add to the cost. Be prepared for extra costs that may arise from unexpected complexities or design changes. Accurate budgeting will prevent financial stress and a smooth extension project.
House extensions come in many shapes, types and sizes each serving a different purpose and adding varying amounts of value and space to a property. The main types are single storey extensions, double storey extensions, conservatories and more unique options like side-return and wrap-around extensions.
Single storey extensions are a popular choice for homeowners who want to add extra living space without changing the fabric of their existing property. They are a relatively straightforward way to add a new kitchen, living room or dining room. Costs for these extensions range from £2,200 to £3,300 per square metre in London and more in other areas. Factors that impact the cost are project complexity, size and finishes. A 15 square metre extension would cost between £22,500 and £37,500 and a 50 square metre extension would cost between £75,000 and £125,000. Economy of scale can apply so the per square metre cost reduces for larger projects. Final costs will depend on flooring, fittings and fixtures with custom choices adding to the cost.
Double storey extensions add value by extending both the ground and first floor of the property. On a per square metre basis they can be more cost effective than single storey extensions with costs between £1,500 and £2,450 excluding VAT. Although a bigger investment double storey extensions are estimated to be 50% to 75% more expensive than a single storey extension with total costs around £40,000 to £50,000. This option uses the property footprint by building up and adds extra room for multiple rooms and saves on construction as only one foundation is needed. When budgeting for a double storey extension you need to factor in the cumulative costs of fixtures and finishes for the added rooms.
For homeowners looking for a cost effective way to gain extra space conservatories are a good option with the average conservatory costing around £15,000. Simpler structures like the lean-to conservatory start at around £5,000 and more complex Victorian or Edwardian styles cost between £10,000 to £15,000. If you want premium materials like oak framing the cost will be between £30,000 to £40,000 reflecting the quality and longevity of the build. Conservatories are quicker to build but have limitations as they are not always considered habitable year round spaces due to temperature control issues and the services that can be installed. But they are a good option for those who want extra space without a full blown extension project.
Now you know the types of house extensions and their costs you can start your extension project with informed expectations and budget.
Extension costs can be influenced by many factors with the average cost in the UK being between £1,500 to £2,500 per square metre. But these costs can vary depending on several key aspects like size, type and materials used. Although a bigger extension size will cost more overall the cost per square metre can be more cost effective as the project gets bigger – especially if it’s a multi-storey build.
As for the type of extension single storey extensions are the cheapest option and multi-storey or wraparound extensions are more expensive due to their complexity and the extra structural work involved. The quality of finishes and the complexity of the design can also add to the basic rates and make it more expensive for those who want a high end finish or specific architectural features.
The location of your property will also impact the cost of your house extension. For projects outside of London the costs will be lower. London has higher labour costs which will add to the overall cost. For example a house extension in Manchester will cost between £1,200 to £2,000 per square metre reflecting the lower cost of living in the North West. In London the costs will be much higher.
Architects and builders also charge less in the North so that adds to the regional variations in costs. Homeowners should also consider additional costs that can add up like charges for exceeding off road parking during the build phase.
The design complexity of an extension will impact the overall cost. High complexity designs with complicated floor plans, unusual shapes or high ceilings will require more resources and technical expertise and will cost more. Multi-storey extensions require more structural reinforcement so will cost more than single storey extensions.
Functionality adds to complexity when it comes to kitchen or bathroom extensions which are generally more expensive than bedrooms or offices. Early on in the planning process homeowners should gauge the complexity and match it to their budget to avoid cost overruns on advanced features or high end finishes.
Planning permissions is part of the process of a house extension. A standard planning application costs £206 and is required when permission is needed for the extension. It’s also recommended to get a Lawful Development Certificate even when permission is not required to prove the construction is legal.
Extensions that go over certain limits on property land coverage, roof height or eaves proximity will automatically require permissions. Add to that any plans that involve structural changes like balconies or changes to roof design need to be checked against planning guidelines. Matching your extension to these rules will save you extra costs and will be beneficial if you sell the property in the future.
The location of your property will impact the cost of an extension. London is the area with the highest house extension costs mainly due to the labour costs. The average cost of a house extension will be much higher in the capital compared to the rest of the UK.
Moving up to the North West like Manchester the costs will be more affordable. Here the costs will be between £1,200 to £2,000 per square metre reflecting the lower property and construction costs in this area. The North of England will further this trend with more competitive architect and builder fees for house extensions.
When planning an extension you should also consider the location specific costs for your property. For example if off road parking is not available you may need to factor in the cost of a parking permit.
Here are the rough estimates for location based pricing:
Design complexity is a big factor in house extension costs. Complex designs with unusual shapes, angles or high ceilings will cost more due to extra materials and specialist labour. This is more evident in multi-storey extensions where the structural demands are higher than single storey extensions.
Specialist spaces like kitchens and bathrooms have their own challenges and therefore cost more than a home office or playroom. These rooms will require extra plumbing, electrical work and high spec finishes.
Homeowners should consider the design complexity when planning their extension. A simpler design will save costs and help with financial planning and resource management. But aspirations for special features or high end finishes will blow the budget. You need to balance your wants with your budget to avoid cost overruns.
Remember, the key to a successful house extension is knowing how your design choices will impact the cost.
Understanding planning permissions is a big part of managing house extension costs. A planning application fee of £206 is required if the extension needs planning permission. Circumstances that will require permission are where the extension covers more than half the land of the property, goes above the highest point of the roof or has eaves that are more than 3 metres high within 2 metres of the boundary.
Planning permission may not be required for all types of extensions but a Lawful Development Certificate is recommended to confirm the work is within the law. Notably extensions with raised platforms, balconies or changes to the existing roof structure will not comply with planning regulations and may need to be revised to avoid extra costs.
When submitting a planning application for an extension you must comply with the legal requirements. It’s important for the immediate costs but also for future property sales where compliance with regulations can affect the selling process.
Careful consideration of these factors will help manage the overall project cost and avoid extra costs.
When you’re thinking of house extensions the project cost goes beyond the construction costs. Additional costs include professional, administrative and unforeseen costs that can add up quickly. For example site survey fees to identify any potential construction issues are £600 to £1,400. An architect is another big cost, 7-15% of the total extension cost, planning drawings alone are £2,500 to £3,000. Structural engineer services vary depending on the complexity from £400 for minor alterations to £4,000 for major works involving reinforced steel beams or load bearing walls.
The standard planning application fee for house extensions is £206 but some extensions are Permitted Development and don’t require this step, saving costs. However a Lawful Development Certificate which is half the standard application fee is recommended to confirm the work is legal especially when selling the property in the future. Managing these extra costs is key to staying within budget and a successful extension.
These figures are pre-construction costs not including the extra and sometimes unexpected costs that will arise during the extension. Now let’s look at the professional fees for architects and surveyors.
The professional fees for architects are 3-7% of the construction cost so you could expect to pay £2,700 for planning and drawings. Structural engineers will charge £500-£1,000 and surveyors £500-£1,500. If your builder or architect is managing the project for you be prepared for an extra 15-20% on top of the total cost.
Professional services for house extensions add up to 15-25% on top of your construction costs. This is not just because of the complexity of the project but also because of the consultancy from specialist professionals like quantity surveyors or engineers if required.
Groundwork costs are often overlooked but can have a big impact on the overall cost of your extension. Groundwork includes essential elements like laying foundations and drainage and vary depending on the site and soil type. For properties on uneven ground groundwork can be more expensive than flat sites. The soil type may require special materials or techniques which will impact the total groundwork cost.
Extra groundwork costs may arise if existing drainage systems need to be re-routed or re-fitted. To avoid these costs one could try to simplify the extension footprint; complex bases for larger builds will incur higher groundwork costs.
Labour is a big chunk of the overall extension cost. A labourer’s day rate is £100-£160 and hourly rate £7-£15. For skilled tradesmen like bricklayers the day rate is £130-£180 and hourly rate £12-£20 for small tasks.
It all adds up when you look at labour costs for different types of extensions. Single storey extensions will cost around £18,000-£22,000, double storey extensions around £28,000-£30,000 so you can see the cost of extra living space. The labour market also varies geographically as shown by the difference in costs between builders in different areas – a 25m² extension in Kingston upon Thames will quote £29,975 and in Birmingham £17,972. For complex projects like wrap around extensions labour costs can be £28,000-£60,000. Extension TypeThese are rough estimates to give you a baseline budget but you need to account for the variance in labour costs depending on the size, type and finish of your extension.
A house extension project is broken down into stages, each with its own tasks and costs. A clear budget that covers the whole process is key to the smoothness and financial certainty of the project. The project starts with the planning permission and design phase which will require the services of an architect who will cost £500-£1,000. This stage ends with all approvals and is the foundation for the physical build to follow.
The build phase is the core structural work – the building of the foundation walls, roofing, windows and doors. This is the most intense labour and can take 6-12 weeks depending on the size and complexity of the project. Then the project reaches the ‘first fix’ stage where electricians and plumbers fit the services. The ‘second fix’ follows where the cosmetic work begins – flooring and kitchen or bathroom fittings.
Finally the extension is complete with a detailed snagging and handover phase where everything is checked and signed off. It’s not uncommon for this stage to reveal minor imperfections or ‘snags’ that need to be sorted out and this will add 1-2 weeks to the timeline. Budgeting for each stage accurately is key to avoiding unexpected costs.
Before the physical build of a house extension can begin the planning and design phase must happen. A sensible first step is to check the extension will comply with local planning permission regulations. Planning applications cost around £200 but additional fees apply if you want to use council consultation services which will be £50-£150.
The detail is key and an architect can be very useful in navigating the complexities of the regulations especially for properties in conservation areas. An architect will ensure compliance but also design the extension to fit the homeowners vision within the legal and practical constraints. Constraints include not covering more than 50% of the land or exceeding the height of the existing property. Good planning and design will make for a smooth extension project and prevent costly post build regulatory snags.
The groundwork and foundation is the foundation of a stable and secure house extension. If the ground is uneven excavation costs can be £30-£50 per cubic metre and new drainage systems can be £550-£1,800 depending on the size of the project.
Complexity in the groundwork will increase overall costs so keeping it simple in the new extension will reduce costs. Soil type may require special foundations which will add another layer of cost. But good groundwork is essential to eliminate future structural problems and to have a solid base for the build to proceed safely.
The physical build begins with structural work and framing. Laying the foundations will cost between £100-£130 per cubic metre so budgeting for this is crucial as it’s time consuming and essential for stability.
Then the build up of walls and frames made from timber and bricks can cost £800-£1,600 per square metre. Steelwork is required in some projects and can cost £20-£35 per square metre (depending on the structural engineer). Roof functionality and aesthetics also comes into play with more complex designs requiring more resources and labour. Working closely with architects and builders is key during this phase to navigate the structural complexities of a house extension.
Finally the extension takes shape in the internal finishing. Costs vary greatly here with bathroom fitting prices ranging from £3,000 to £10,000 depending on the fixtures. Flooring, kitchen units and other fittings will greatly impact the cost or saving in the budget and luxurious materials or custom features can double the cost of the extension.
Internal finishing is also expensive with all the choices in lighting and electrics especially with kitchen integrations that require complex wiring for new appliances and sockets. This last stage will give the extension the desired look but also has the potential to add to the overall cost of the project so decisions made here are crucial.
When building a house extension it’s important to understand the project timelines to manage expectations and coordinate with tradespeople. Here are some general timescales for the type of extension:
Please note these timescales are approximate and actual build times may vary due to weather, planning permission, material and labour availability. Always discuss timescales with your builders and include some contingency time for any unexpected delays.
When building a house extension having accurate budgeting and costing tools is key. The average cost of a house extension in the UK is between £1,500-£2,500 per square metre. This is a starting point for homeowners to work from and create a rough budget based on the overall extension size and design. For example a homeowner looking to add a 30m² single storey extension can expect a project cost to be between £45,000-£75,000. But this is a rough estimate and the final cost will vary.
To avoid any nasty surprises and to make the planning process smoother it’s best to get comprehensive itemised quotes from several contractors. This will give you a clear picture of the costs and allow you to compare services and pricing. A detailed cost breakdown, possibly done through a spreadsheet template is a very useful tool. This template can include various project elements such as labour costs, materials, professional services and any other costs.
When it comes to the planning stage there are fees to consider. The planning application fee for house extensions is £206 although a Lawful Development Certificate for permitted developments which is half the fee of a full planning application can give you peace of mind and is an asset for future house sales.
The house extension cost calculator is an advanced tool to get more tailored estimates for house extension costs. It takes into account the type of renovation, the rooms being renovated and even the location through the postcode. This online tool makes planning more sophisticated and helps you predict costs throughout the entire extension process, including professional fees and contingency costs for unexpected expenses.
Although they provide detailed projections these calculators should be used as a supplement not a substitute for quotes. The figures they give are best used as a rough guide. Homeowners need to understand that these calculators don’t give fixed final costs but a rough estimate to help shape your initial budget expectations.
In summary house extension costs in the UK vary. Average costs range from £22,500 to £125,000 depending on the type and finish of the extension and cost per square metre is between £1,500 and £2,500. Kitchen extensions which are a common project can range from £7,000 to £26,000. Remember to factor in extra costs for professional services, planning permissions and contingency costs for unexpected expenses which can all impact on the final budget.
Before you start an extension get detailed quotes from several contractors to get a full budget. This will give you a more realistic budget and reduce the risk of nasty surprises. Planning and budgeting is key to a smooth and successful extension to your living space and building regulations and local planning requirements.
Be aware of all the factors that can impact the extension cost to manage your expectations and stay within your means.
Choosing the right builder is key to a successful home extension. At Danesfort we deliver quality on time and on budget. We have extensive experience working on home extensions in the London area.
Danesfort ensures all projects comply with planning permissions and building regulations. We offer clear contracts that outline scope, timelines and payment terms so you’re fully informed from start to finish.
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