A side extension is a type of extension that involves adding structure that protrudes out from the side of a property, filling in the narrow passageway next to the main building (i.e. the side entrance). The exact design details of a side extension can differ in a range of ways, however.
Side extensions can not only introduce additional living or/and storage space to a property but potentially add value to a home (possibly somewhere in the range of 10-20%). All that said, it’s important to consider whether a given side extension project will be within your budget while considering the upfront costs and any additional costs that may apply.
In the following guide, we’ll discuss the average prices of a side extension, break down these costs into key price elements (e.g. the price of labour and supply only costs), and other related topics such as additional costs that may apply. Let’s dive in!
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Planning and Permission Costs
Planning permission may be required to have a side extension built on your property. That said, in order to avoid a full planning application (i.e. when it is deemed ‘permitted development’), here are the rules that apply:
- If the extension extends beyond the original house’s side elevation it cannot go beyond a height of four metres
- If the extension extends beyond the original house’s side elevation it may be a single storey side extension only
- If the extension extends beyond the original house’s side elevation its width may not exceed half the width of the original house
- The property cannot be on article 2(3) designated land
If your proposal is outside of any of these rules, you’ll need to make a planning permission application. This should cost about £260. It often takes as much as eight weeks for a planning application to be approved. Even where planning permission is not needed, you’ll need the local authority to sign off on your proposal.
Any side extension build must adhere to building regulations. This usually comes with a cost of several hundred pounds, although it can depend on the size, type or/and cost of the extension in question. Other approvals may be needed, so if in any doubt, you can always consult with your local council for clarification.
Beyond that, planning costs can also apply if you need to hire one or more professional services for this phase of the project. For example, you may need to hire an architect or professional designer to draw up your proposed side extension. Moreover, a surveyor may be required too.
It’s important to note that hiring an architect may cost you several thousand pounds or around 5-10% of the total cost of the side extension construction. That said, an architect generally will not be needed. Homeowners are more likely to require an architect for side extension builds that are complex or unusual.
A surveyor will be needed in certain scenarios also, such as if the extension is to be built on an adjoining wall between your property and that of your neighbours. In this case, a surveyor would be needed to make a Party Wall Agreement. This sort of work may cost you somewhere around £1,000 if required
Construction Costs
Note: All of the costs below comprise the estimated price of labour and the materials required as a sum total.
So, what is the cost of a side extension? In this section, we’ll look at the average total costs of having professionals install side extensions of varying sizes.
Here are the average costs for installing budget-friendly side extensions:
- Single-storey 20 Square Metre Side Extension - £20,000 to £25,000
- Single-storey 25 Square Metre Side Extension - £30,000 to £38,000
- Single-storey 30 Square Metre Side Extension - £38,000 to £43,000
- Double-storey 40 Square Metre Side Extension - £50,000 to £60,000
- Double-storey 60 Square Metre Side Extension - £70,000 to £90,000
- Double-storey 80 Square Metre Side Extension - £100,000 to £125,000
Here are the average construction costs for standard side extensions:
- Single-storey 20 Square Metre Side Extension - £30,000 to £35,000
- Single-storey 25 Square Metre Side Extension - £40,000 to £47,000
- Single-storey 30 Square Metre Side Extension - £52,000 to £62,000
- Double-storey 40 Square Metre Side Extension - £70,000 to £85,000
- Double-storey 60 Square Metre Side Extension - £100,000 to £130,000
- Double-storey 80 Square Metre Side Extension - £150,000 to £185,000
Here are the average prices for high-end side extension builds:
- Single-storey 20 Square Metre Side Extension - £30,000 to £40,000
- Single-storey 25 Square Metre Side Extension - £45,000 to £57,000
- Single-storey 30 Square Metre Side Extension - £65,000 to £75,000
- Double-storey 40 Square Metre Side Extension - £70,000 to £90,000
- Double-storey 60 Square Metre Side Extension - £110,000 to £140,000
- Double-storey 80 Square Metre Side Extension - £170,000 to £210,000
The total cost of having a side extension built will primarily comprise the price of labour and supply only costs, although other costs like that of waste removal (for more on potential added costs, skip to the ‘Additional Costs’ section below) may also make up the overall price.
The cost of having a side extension added can be influenced by a range of factors including the size and type of extension, the materials used, where you are located and how accessible the work areas is.
To explain these cost factors, firstly, it goes without saying that a larger side extension will generally cost more. This is not only because of the labour cost likely being higher (due to more time and work being required) but the fact that more material will be needed, which will increase the supply costs too. The type of side extension (i.e. the specific design) can also affect the amount of time needed to complete the project and potentially the amount of material needed or/and the price of the materials required too.
Where you live also matters. This is because the price of labour differs throughout the UK. While labour costs tend to be above average in the southeast of England, they are usually below average in areas such as northern England, Scotland and Northern Ireland. Beyond that, the more accessible the work area is, the sooner it should take for professionals to construct your side extension and therefore the less costly it should prove.
When considering having a side extension built, just be sure to opt for a size, design and cost that is a good fit for you and your household. Of course, if in doubts you can always chat the side extension installation service you decide to hire.
Labour Costs
As discussed, the overall cost of a side extension will comprise the labour and supply only costs. As for the price of labour in particular, a builder is likely to charge about £100 to £300 per day. In total, you may end up paying somewhere in the region of £2,000 to £18,000 for the entire project.
Of course, several builders may be needed, although you may only require one builder (or none depending on who performs the work overall).
Other labourers that may be required (and their estimated total cost for a side extension build) can include:
- Electrician - £200 to £1,000
- Bricklayer - £1,000 to £9,000
- Plumber - £200 to £1,000
- Window Fitter - £200 to £500
- Carpenter - £1,000 to £3,000
Beyond that, you may want to hire an architect, although again, they won’t always be needed. If required, however, an architect may charge around £2,000 to £8,000 in total.
As you can imagine, the total labour cost can be influenced by a whole host of factors. Firstly, the type and number of professionals being hired will play a significant role in determining the overall price of labour.
Other factors that can influence the cost of labour includes your location, the scale of the project (which will determine how long the work will last), and ease of access.
Material Costs
The price of materials used for a house side extension can vary significantly too. In this section, we’ll look at the average price of different side extension materials.
Here is the estimated cost of different primary materials that can be used to make up a side extension:
- Brick - £1,000 to £2,000 for every 1,000 bricks
- Glass - £3,000 per m²
Of course, the cost of glass and bricks can differ depending on the type of glass or brick being used. For example, double-glazed glass costs more than single-glazed glass, whereas triple-glazed is costlier than double-glazed glass.
When it comes to the roofing, you’re looking at spending approximately £2 to £5 per roof tile, £30 to £45 per m² for felt roofing and £50 to £70 per m² for EPDM rubber roofing.
Further, other potential building materials to consider are sand (approx. £40 to £80 per ton), cement (approx. £50 to £100 for 10 bags of cement), and concrete for foundations (approx. £40 to £70 per ton).
The average door costs somewhere in the region of £500 to £2,000. Here are the supply only costs of different types of doors in the UK:
- Wooden Door - £200 to £2,000
- uPVC Door - £500 to £900
- Composite Door - £600 to £2,000
- Metallic Door - £500 to £2,000
- Bespoke Door - £1,000 to £5,000
Finally, when it comes to the price of windows, this can differ depending on the type of material used for the window frame and the type of glass used (i.e., single-, double-, or triple-glazed). Windows generally cost somewhere between £500 and £2,000.
Here are the costs of different types of double-glazed windows (material costs only):
- uPVC Window - £500 to £700
- Timber Window - £700 to £900
- Aluminium Window - £800 to £1,000
Notably, double-glazed windows usually cost about 50% more than single-glazed units and triple-glazed windows generally cost 10-20% more than double-glazing. That said, unless money is no object, double-glazing is arguably a more cost-effective option than triple-glazing.
As you can see, there are many potential material costs that can also vary significantly depending on a range of factors, including the type of material and nature of it. The quality or supplier can also affect the cost of different materials.
Related to the fact that the size of the side extension is a key cost factor, this can also related to the nature of the design (e.g. when considering a side return extension cost or even a narrow side extension cost).
Additional Costs
It’s important to consider that a range of additional costs may also apply. In this section, we’ll look at some of the most notable examples.
Firstly, though, it’s important to note that you’ll want to be prepared for unforeseen costs. Therefore, your budget should have quite a of leeway (of at least several hundred pounds, if not several thousand pounds).
So, considering the potential for added costs and discussing this with the service you choose to hire can help make the project run smoothly with a lower risk of headaches and unexpected challenges.
Insurance
You’ll want to make sure that your side extension is insured. There’s a good chance that your current house insurance will not cover a new extension, unless you pay extra. One way or another, you’ll want to get in touch with your insurer to discuss this.
You may find that you’d like to go with another insurer, though again you’ll need to make certain that this is an option depending on what the rules are relating to your current insurer. Insurance may end up under £100 a year, particularly if opting for contents insurance only, though in other cases it could cost you several hundred pounds annually.
Temporary Accommodations
Depending on the complexity, type and duration of the work involved, you may decide feel it’s best to spend time elsewhere. Of course, this won’t cost (or at least not cost) much if you can stay with friends or family.
That said if those options are impractical, you’ll want to look into other forms hospitality (e.g. hotel, Air BnB, etc.). If you decide to stay in temporary accommodation, be sure to consider how this might affect your budget and that you can book in for the amount of time needed.
Landscaping Post Construction
Once your side extension has been complete and fully installed, including all interior aspects such as wiring and plumbing, if applicable (of course, these sorts of jobs must be done by professionals), you may want to look into landscaping.
With a side-extension suddenly taking up more room beside your garden, you may want to look into ways to change the look and layout of your garden, whether it be in relation to the flowers growing, plant pot placements or/and water features.
Relatively simple landscaping work should cost a few £100, whereas more complex jobs (e.g. the addition of a patio), could bring the cost of post construction landscaping to several hundred or even several thousand pounds. So be sure to consider this carefully and well in advance.
Cost-Saving Tips
When having a side extension built, you’ll want to consider how you can save money without compromising on quality.
Best Overall Tips
Here are some standout tips worth keeping in mind:
- Opt for a budget-friendly side extension that is still of substantial quality
- Think about hiring a project manager to help get the most for your money
- Compare the quotes of several companies/services (e.g. extension-building company) so that you can weigh up several options before deciding who to hire and hopefully secure good value for money
- Considering going with a relatively small side extension once it can still meet all your needs and expectations
- Look into low-cost but high-quality materials that can be suitable for your side extension project, including within the context of the various materials and fittings to be included in your extension
- Consider cost-effective eco-friendly materials if you want to balance a reasonable budget with an environmentally friendly installation (e.g. use of bamboo where suitable, FSC-certified wooden windows, recycled metal roofing or even solar panels to power your side extension if feasible)
- Opt for a relatively simple design to the extent possible
- Plan ahead and talk with the side extension construction team in detail (without incurring added fees for extra time engaging, where possible – be sure to bring this up if you are concerned about being billed extra
Long-Term Savings
Beyond that, it’s also worth considering approaches that can help you save in the long-term, such as the use of durable materials that won’t break the bank.
For one, you should consider materials that are made to last, while opting for reliable products that provide decent value for money. Some products may prove too expensive while others may be cheaper but potentially not as sturdy, so it’s important to weigh a range of factors up when determining what could be used to make your side extension.
Some examples may include uPVC or aluminium windows, uPVC or metallic doors and EPDM rubber roofing. Be sure to discuss this with the side extension construction service you wish to hire.
Final Thoughts
Ultimately, budget planning is key to ensuring that you can not only afford the total cost (including potential added costs) of a side extension but to do so in a planned way that is thought-out to minimise stress and complications.
What’s more, cost management is another essential aspect to getting the right-side extension for you. You should look at ways to keep the cost down (as discussed earlier) but without sacrificing quality. Working closely with professionals (while staying within your budget) can help ensure you get a great outcome for your property and bank account alike.
A well-planned and well-executed side extension can provide a long-term addition to your property that offers more living space and potentially additional storage space too. What’s more, a side extension may increase the value of your property, as well as its kerb appeal, which is perfect if you think you may ever decide to move.
Finding the right people for the job can lead to a high-quality and visually striking side extension, expanding your home and what’s possible within its interior for years to come!
Sources
https://urbanistarchitecture.co.uk/side-extension/
https://www.planningportal.co.uk/permission/common-projects/extensions/planning-permission
https://www.greenmatch.co.uk/doors/cost