Many people in the UK want more living space but don’t want the hassle and expense of moving house. The money-saving solution is to build an extension to your existing home. By careful planning, you can often provide as much space as you need for yourself and your family by creating either a loft conversion or a ground floor extension. There are many types, and it’s up to you to choose the best for your circumstances and save money. Average bungalow extension costs range from £1,200-£2,800/m2 and take 6-12 weeks to complete, depending on the type, quality and size.
This guide describes the various types of extensions you can build, what regulations you must comply with, how to save money, and how to choose a competent contractor.
Main Topics
Bungalow Extension Cost Breakdown
Many factors affect the price of extending your bungalow, such as the property’s size, the construction material’s quality, and where you live. And juggling all these variables can be tricky. But, to give you a start, the table below gives you an idea of the expected costs when researching quotes.
| Bungalow Extension Type | Estimated Floor Area | Construction Time | Estimated Cost/m2 | Estimated Cost |
|---|---|---|---|---|
| Roof Extension | 20m2 | 6-8 weeks | £1,300-£2,300 | £26,000-£46,000 |
| Loft Extension | 20m2 | 6-8 weeks | £1800-£3,050 | £36,000-£61,000 |
| Dormer Extension | 30m2 | 8-12 weeks | £1,200-£2,050 | £36,000-£61,500 |
| Ground Floor Rear Extension | 30m2 | 8-12 weeks | £1,200-£2,700 | £36,000-£81,000 |
| Ground Floor Side Return Extension | 35m2 | 8-12 weeks | £1,400-£2,700 | £49,000-£94,500 |
| Ground Floor Wraparound Extension | 45m2 | 8-16 weeks | £1,500-£2,800 | £67,500-£126,000 |
*Disclaimer: The estimated costs and durations included in this guide were correct at the time of writing (September 2022). Contact up to four professionals for quotations using our website for actual calculations.
Depending on its style and size, a typical bungalow extension costs between £1,200 and £2,800/m2 and will take six to twelve weeks to finish. But, you can build several extension types, each with a typical price range depending on the style and size.
Roof Extension
Extending the bungalow’s roof involves lifting it and adding an extra half storey. Generally, homeowners do this when they need extra headroom in the roof space, and it’s possible to raise the height of the bungalow to the full height of a two-storey house, subject to planning constraints.
Typically, a 20m2 roof extension will take 6-8 weeks to complete and cost £26,000-£46,000.
Loft Extension
Many bungalows have enough floor area in their lofts to provide at least two full-size bedrooms with a shared shower room and toilet. However, building regulations state that the ceiling height must be at least 2.3m from the floor. Therefore, if your roof doesn’t offer this clearance, you will also need to lift the roof (see Roof Extension).
Loft conversions are much cheaper than a full extension. But, you will probably have to strengthen the existing joists in the loft, install skylight windows and provide plumbing at extra cost, if including a bathroom.
Typically, a 20m2 loft extension with strengthened floor joists takes 6-8 weeks to build and costs £36,000-£61,000.
Dormer Extension
A dormer extension is a method of extending the functional floor area of a loft by providing additional headroom. The extension protrudes from the roof’s slope, and rather than using a skylight, it uses a dormer window and a separate small roof over the extension, with many different dormer windows and roof styles to choose from. And when constructed well, they can create a fantastic feature for any home, with large dormer windows allowing extra daylight into the new living space. As long as the dormer roof height isn’t higher than the main roof ridge and the dormer extension complies with certain planning constraints, you don’t usually need to apply for planning permission.
Typically, a dormer extension of 30m2 takes 8-12 weeks to complete and costs £36,000-£61,500.
Ground Floor Rear Extension
All ground floor extensions enlarge the usable floor area but require foundations, a concrete floor, additional exterior walls and a separate roof. Therefore, the price increases significantly.
As the name suggests, a ground floor rear extension connects to the rear of the bungalow. But, in practice could be built onto the side elevation, planning constraints and building regulations permitting. Many householders construct the extension across the entire width of the structure and typically use it for additional living room space and a larger kitchen or utility room. Because it’s outside the existing structure’s footprint, the extra space needs foundations, external walls and a roof. Furthermore, to link the extension to the rest of the house, many people partially remove the bungalow’s exterior wall to provide open-plan access.
Typically, a ground floor rear extension measuring 30m2 takes 8-12 weeks to complete and costs £36,000-£81,000.
Ground Floor Side Return Extension
A bungalow’s side return extension infills the space commonly found between semi-detached properties. Generally, a side return tends to be a narrow, dark and underused space. But, adding this space to an existing room like a kitchen can considerably improve the room’s proportions.
Typically, a 35m2 ground floor side return extension takes 8-12 weeks to complete and costs £49,000-£94,500.
Ground Floor Wraparound Extension
A ground floor wraparound extension combines a side return and a rear extension. In practice, it creates an L-shaped space, adding depth and width to your existing home. Unlike side return or rear extensions, which often won’t need planning permission if built individually, a wraparound extension often requires planning permission, which might limit the extra floor area that this type provides.
Typically, a 45m2 ground floor wraparound extension takes up to 16 weeks to build and costs £67,500-£126,000.
Bungalow Extension Price Factors
When researching estimates for your bungalow extension, it’s essential to consider several important factors that might significantly affect the price of the completed work. But, carefully planning the design makes it possible to save a significant amount of money without compromising on quality or craftsmanship. The following are factors which can affect the overall cost of your project.
Architect and Structural Engineer Fees
Depending on the size and design of your bungalow extension, you will probably need an architect or structural engineer to produce load calculations and detailed drawings for building regulations, your building contractor and, potentially, the planning submission. Fees can be a lump sum or equal to 3%-7% of the project value. Furthermore, consider the fees required for quantity and land surveyors (£500-£1,500).
Size
As you’d expect, large extensions use more materials and labour, costing more to build than small ones.
Location
Where you live in the country can affect the cost of professional fees, materials and labour. Generally, southeast England is the area with the most expensive living costs. So, expect labour rates to cost more in these areas. The average hourly rates in this area can be £4-£8/hr higher than elsewhere in the country. You will also find that fees set by the local council also vary with location, and you should contact its planning department for the scale of fees.
Style
The style of your bungalow extension will affect the cost. For example, external timber cladding is generally more affordable than brick walls. Also, timber-frame panels and roof trusses are more cost-effective than masonry walls and cut roof timbers. Speak to your architect about the relative affordability of construction methods and choose one that best suits your preference.
Quality of Materials
Using higher quality materials will increase the quality and value of your project. But will also increase the overall cost to build.
Groundworks
Unless you extend the roof, you must excavate and pour foundations and a concrete floor when extending your living space. This additional groundwork increases the overall expense.
Stairs, Windows and Doors
The number and type of windows and doors add to the overall price. Typically, building regulations require double-glazed windows. But, you can install triple glazing to increase your home’s thermal efficiency, if you wish. Furthermore, if you add another storey to your bungalow by converting the loft, you must install suitable stairs. Factor these extras into the overall project cost.
Purpose of the Room
Added expense will be minimal if your extension is a living, dining or bedroom. However, suppose you intend to have another bathroom, toilet, kitchen or utility room. In that case, you must add extras such as a bathroom suite, kitchen units, and the additional plumbing and electrical work needed in these rooms.
UK Planning Permission & Building Regulations
Loft Conversions
Although the various types of loft conversion are different, they must all satisfy the requirements of planning permission and building regulations.
Protected Species
To consider your project’s effect on protected species such as bats, you must have a survey done. If the survey finds protected wildlife, the council might postpone permission until a different time of the year or refuse it altogether. See Planning Portal for more details.
Planning Permission
As long as the loft conversion complies with specific limits and conditions, it’s classed as a Permitted Development and won’t need planning permission. Generally, the finished extension must appear similar to the original house, the extension’s volume must not exceed certain limitations, and the new roof’s height must not exceed the existing one. For more details, visit this Planning Portal page for the Permitted Development of loft conversions.
Building Regulations
The proposed loft conversion must comply with the current building regulations. Generally, the project must have:
- A safe fire escape.
- The new floor must be strong enough to withstand the additional loads.
- The existing building structure isn’t compromised.
- There is a safely designed flight of stairs.
- You must have suitable sound insulation between the conversion and the remainder of the house.
For more information, this Planning Portal webpage details the regulations that apply to a loft conversion.
Ground Floor Extensions
As with loft conversions, there are rules that, when complied with, allow you to build an extension to your bungalow without applying for planning permission.
Planning Permission
There are many requirements and limitations you must comply with to keep within the permitted development rules. Look on this Planning Portal webpage for further information on extensions. However, remember that if you want a ground floor wraparound extension, it’s unlikely that the plans will comply with permitted development, and you must apply for planning permission.
Building Regulations
All bungalow loft conversions and ground floor extensions must comply with the existing building regulations. The following list gives you an idea of the construction regulations you must follow and provides links to the relevant Approved Documents for more information.
- Bathrooms and Kitchens
- Electrical Work
- External Walls
- Foul and Surface Water Drainage
- Internal Walls
- Roof
- Windows and Doors
You must also remember that there will usually be fees for building regulations inspections unless you use a building contractor who belongs to a government-approved Competent Person Register. Check with your council offices for more information.
Party Wall Act
The Party Wall Act prevents building work from affecting the structural integrity of neighbours’ property or shared walls and boundaries. Typically, this applies to terraced houses and semi-detached properties and relates to undermining a neighbour’s foundations or garden boundary walls.
How Long Do Bungalow Extensions Take?
Generally, a bungalow extension takes from 6-16 weeks depending on several factors:
- Weather conditions – Cement and concrete have problems gaining full strength in extreme weather. This includes drought, heavy rain, extreme heat and temperatures below 4⁰C.
- Time of year – This determines the weather and often causes downtime, especially if you haven’t made the extension’s shell watertight.
- Size of extension – a small extension will take less time to build than a large extension.
- Type of extension – a loft conversion generally takes less time to build than a ground floor extension. Usually, loft work takes place inside except when fitting windows. So, it doesn’t take long and doesn’t require groundwork or a waterproof shell, unlike ground floor extensions.
- Workforce availability – Certain trades are hard to book to a specific date, especially if your project timeline changes due to weather and materials availability.
- Are you using professional contractors or building the extension yourself? – DIY projects usually take longer than using a professional contractor. But, you save money and aren’t at the mercy of contractors’ availability.
- Materials availability – Some materials, especially if they are unusual or difficult to source, take longer to deliver. Therefore, they might hold up the project timeline.
Don’t plan starting dates until you have all the funding and the local council’s planning department and building control office have approved your plans. Sometimes, the council can take a long time to grant permission, especially if you need a protected wildlife survey or the project comes under the Party Wall Act.
What To Ask Your Potential Builder
Depending on your project, you may require different tradespeople. Of course, if you are hoping to save money by doing some of the work yourself, it’s still worthwhile calling in a few specialist trades for the tricky bits. For example, use a contractor for:
- Foundations – Getting these right is essential, as the structure relies on solid and level foundations. A building inspector will inspect these thoroughly.
- Plumbing – Drainage, mains water supply, and central heating must comply with separate sets of regulations and once again will be thoroughly checked. Don’t forget that a slight mistake from a DIYer might cause 100mm of water in the living room in the middle of the night or a leaking drainpipe churning sewage into the garden.
- Electrical – There are many minor electrical jobs that a DIYer can do. However, most work involving wiring an extension needs professional skills beyond an amateur’s expertise. Don’t be tempted to do major work, as your insurance company won’t pay out for electrical fires unless you have proof that a Part P electrician did the job.
- Roofing – The roof is an essential part of an extension and must be watertight and withstand high winds. Use a professional roofer who can do all aspects of the work. Once again, an insurance company might not pay out on your policy if you didn’t use a professional roofer.
How to Choose a Qualified Builder
Insurance
One of the most important things a professional builder has is suitable insurance. Ensure they have General Liability Insurance to cover:
- Damage to your property
- Injury and death to you, your family and other third-party persons
Qualifications and Experience
The best contractor has registered on the Competent Person Scheme. They’ve satisfied the local authority of their skill and expertise and can sign off their work as complying with the building regulations. Otherwise, if you do it yourself, the building control officer will continually look over your shoulder and check your work before you can move on to the next stage. And, if it’s not up to the required standards, you must replace the faulty work at your expense.
Quotation
Get a written quotation specifying the scope of work, materials, cost, and payment terms.
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Building an extension is probably the most affordable way to gain more living space without moving house. But, there are many rules and regulations you must comply with to ensure the standard of work meets the required level. Although you can save money by doing some of the work yourself, select a qualified and competent person to do those parts that need a professional.
Complete the form on this page, and you’ll receive up to four local bungalow extension quotes. Once you have them, you can choose the best quote for your circumstances in the privacy of your home.