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How Much Does An Extension Cost

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  • 25-08-2022
How Much Does An Extension Cost

How much does an extension cost in the UK? We look at extension project costs and if an extension right for your home.

Depending on the local real estate market, an extension's price per square metre may change. Therefore, depending on where you reside, even small-house addition ideas may prove expensive. The standard presently is £1,500 per square metre for a low-to-medium-end addition.

This increases to between £1,800 and £2,000 per square metre in London and the Southeast. You may get a straightforward 4x5m single-story addition for £30,000. This solely covers building expenditures; accessories and interior furnishings are not included.

You may get a modest 3mx6m two-story expansion for £55-60k (build costs only). A tiny 3x6m two-story expansion with architect-designed cladding, custom windows, and a designer kitchen costs between £70,00 and £80,000.

Due to greater labour and material expenses in London and the Southeast, prices are higher than in the rest of the UK. A wraparound expansion, which combines a rear and side extension and connects at the corner, costs £65k for a single-storey side return extension with VAT included. Rear extensions start at £55-60k.

A shell-only extension consists of the external build only - foundations, brick walls and a roof - giving you a watertight foundation for future work.

That means you'll have no internal walls (no plastering or stud work), no utilities, no glazing and no flooring (beyond a concrete floor).

This is useful if you'd like to carry out the non-structural work yourself therefore a shell-only extension is a good way to save money.

This is also a good option if you'd like to do the work in stages as you get the funds available or wish to use a specialist for the internal design.

 How Much Does An Extension Cost UK?

Shell extensions cost around £750-£1,500 per square metre (m²). A shell-alone addition includes simply the external construction - foundations, brick or block walls, and a roof - providing a waterproof base for future development. This implies you won't have any internal walls (no plastering or stud work), utilities, glass, or flooring (beyond a concrete floor).

A shell-only enlargement is a great way to save money if you plan to handle the non-structural work yourself.  Additionally, this is a great option if you want to carry out the work in stages as money becomes available or if you want to engage a professional for interior design. The average cost of a shell extension is between £750 and £1,500 per square metre (m²).

What are The Costs of Extensions Projects?

Before you can get an exact estimate of the costs related to your expansion, you must take into consideration a number of elements. The size of your extension, the materials you use, and other factors, such as the quantity of glass, for example, will all have an impact on the overall cost of extending, even before accounting for additional costs like surveys, structural engineer fees, planning approval, and more.

This is a handy reference that provides some preliminary figures that you can use to begin thinking about your project since it's crucial to understand how much an extension costs in order to evaluate whether it's even financially feasible to be constructing one for your house. While it may not exactly match your builders' rates or estimations, and it may vary depending on where you reside in the UK, this information should give you a decent idea of the expenses involved.

Budget between £1,350 and £1,750 per square metre if you're going to construct a simple, box-shaped, single-story addition. Remember that this cost will vary based on where you live in the UK and the build quality you choose.

You might easily pay between £1,700 and £2,500 per square metre in specific South and high-value areas of the UK, which are influenced by a higher cost of living. This is especially true for smaller single-story expansion ideas. So an 8x4m kitchen addition would cost between £43,000 and £80,000.

Basic quality costs between £1,350 and £1,650 per square metre, while excellent quality costs between £1,700 and £2,000 per square metre. The pricing range for high quality is between £1,800 and £2,500/m² or more; you should normally anticipate paying 40% more for an excellent finish than a basic finish.

The cost per square metre for a double-storey addition will be in the range of £1,250 and £1,650. That's because you are merely putting up new walls and floor joists, aside from the additional interior fittings and finishes.

Regardless of whether you construct a single or double-storey expansion, a roof and foundations are necessary, and their costs will be similar.

Price per square metre ranges from £1,250 to £1,650 for basic quality, £1,650 to £2,250 for fair quality, and £3,000 or more for outstanding quality.

Your suggested side extension's price will mostly rely on the size of the building, where it will be built, and the calibre of the materials and finishes used. A normal price range might be between £1,500 and £2,000 per square metre, with smaller expansions often costing more per square metre than bigger ones.

The extent of the internal work and any necessary reconfiguration will also affect how much the project will likely cost. The price of merely expanding your living area will be considerably different from the price of moving and installing a new kitchen, for instance.

For a side expansion, homeowners should set aside, on average, between £75,000 and £300,000. The maximum project cost might be as much as you're prepared to spend on the expansion of your dreams. In any case, it's crucial to decide on a maximum spending limit that you are comfortable with and to provide for a contingency reserve.

Despite being by far the most expensive type of addition, basement extensions are becoming more and more popular in the UK since they are an excellent way to increase home prices in areas with a limited amount of space. If space is at a premium or all other options for above-ground development have been considered, basement expansions are an excellent option.

A significant chunk of their price is attributed to the substantial groundwork (which involves moving pipes and tree roots) and construction of a waterproof shell. Considering how specialised these tasks are, there aren't many opportunities for do-it-yourself initiatives to save money.

When it comes to conservatories, a lean-to uPVC construction is at the lower end of the pricing range and may be built for about £5,000. Victorian, Edwardian, L, P, and T-shaped conservatories, for example, are more likely to cost between £10,000 and £15,000 (in PVCU). The price range for an oak frame conservatory is between £30,000 and £40,000.

A 20 m² wood frame conservatory should cost no more than £2,500 per m² (including VAT). With larger projects, the average cost will decrease as the costs of computer design and CNC machining are dispersed across a greater area. This will result in an above-average build.

Quality conservatories seamlessly connect greenhouse building structures to full-fledged additions. The usual rule of thumb is that your conservatory will be considered an extension if it goes beyond the parameters of permissible construction.

Fundamentally, a home remodelling that is considered approved development is exempt from the requirement for a planning permit.

According to English planning legislation, installing a conservatory in your home is deemed "permitted development" as long as these limitations and specifications are met. If any of these specifications aren't met by your conservatory's specifications, planning permission and construction rules will be in force.

The location, soil type, party walls, property type, site access, local authority regulations, and, of course, the size of the existing cellar, among other variables, might affect the cost of the basement. A basement's preparation for design and finishing, including waterproofing, should cost at least £20,000.

Prices would start from roughly £3,000-4,000/m² for situations where excavation and underpinning are necessary to increase the head height or expand the area. Normally, expenditures would rise in accordance with the intended use of the expanded region.

For instance, if a shower or utility room is needed, the cost would increase since more pumping systems will be needed. Although basement additions are by far the most expensive kind of addition, they are becoming more and more common in the UK since they are a great method to raise house values in places with limited room.

Basement extensions are a good choice if space is at a premium or if all other above-ground expansion alternatives have been explored. The extensive groundwork (which includes shifting pipelines and tree roots) and building a waterproof shell account for a large portion of their expense.

Since they are highly specialised duties, there isn't much opportunity for do-it-yourself projects to reduce the cost.

Is An Extension Right For Your Home?

Before you get too involved in the specifics of how much an additional cost is, consider if an extension is financially feasible and acceptable for your home. Is this your permanent address?

In this scenario, an extension is a no-brainer when weighed against the inconvenience of relocating. In terms of money, choosing an extension saves you money on moving costs, lawyers fees, and stamp duty - expenditures that aren't recouped by increasing value the way your expansion does.

However, keep in mind that expanding your property may put you at a higher council tax rate.

If you intend to sell your property, whether soon or later, you must guarantee that you add more value to it than the expansion costs. Before you decide to proceed, speak with local estate agents and study ceiling prices in the region.

Of course, the extension's budget will be impacted by the building method you select. Use concrete blockwork to create an addition if you wish to do it on a budget. It's a system that most builders are familiar with.

Is An Extension Right For Your Home?

Alternative contemporary building techniques, such as structural insulated panels, could be more expensive initially, but cost savings may result from less time spent on the job site, particularly when insulating your addition.

Another option for construction is a timber frame. The price of the frame, related design work, shipping, and on-site assembly are all invoiced together. The benefit of this is cost certainty. If you hire a contractor to undertake the work, most expansions will be subject to VAT on labour and materials at the usual rate of 20%. You can avoid paying the regular rate of VAT on materials while saving 20% on labour by employing nearby tradesmen who are not VAT-registered.

Some remodelling projects are free from VAT if they increase the number of units in an existing house or improve a structure that has been empty for at least two years. To benefit from the aforementioned VAT discounts, you must hire a VAT-registered builder; you cannot claim the VAT on your own.

Several elements must be considered when evaluating the total cost of an expansion. Given the high cost of construction per square metre, it is critical to be aware of any additional charges that may raise the overall cost of your project. The price of employing a surveyor, structural engineer, and architect for your project must be included. It will require time and money to get the necessary party wall agreements, building rules approval and planning clearance (if needed).

The size, form, and height of your expansion will often increase your prices. The larger you go and the more expensive the materials, the greater the cost. Similarly, the sort of building materials you use - brick face, timber clad, or glass - can influence your costs.

The cost of groundworks, such as excavating a foundation, upgrading drainage, or underpinning, will all be factored in. 

Expect to pay more if you want to construct on difficult terrain than if you want to build on something already existent and level. Trees can be more difficult to work with than the extension itself.

Many trees are protected by Tree Preservation Orders (TPOs); therefore, be sure you include any trees when asking for planning approval.

If you remove or change a tree without the proper licence, you might face serious consequences.

Don't forget to account for any additional issues may include soil type that necessitates a certain building technique or material, alterations to the existing structure - any adjustments to steelwork or walls will incur additional expenses; if you're shifting drainage, piping, gas metres, and so on, this will necessitate additional planning and cost.

extension cost

When determining the cost of your expansion, it's critical to comprehend the impact of these variables because changes to just one of them can significantly affect the project's cost. Costs could increase by at least double, for instance, if supply is restricted or there is a major event.

Most builders can complete projects using standard building techniques without the assistance of specialists. The same is true for regular equipment, which is likewise easily accessible and priced affordably. Your prices will increase if you need to hire a professional, locate expensive equipment, or choose a building technique that calls for extra considerations. 

Kirk-Brown Ltd are experienced in producing working drawings for building extension and conversions. These drawings are fully compliant with the related Part of the Approved Documents and can be submitted for Planning Approval and Building Control Approval.

We can additionally create specifications for the project and organise any administration required. If you have any questions regarding our services please simply get in touch to speak with our chartered surveyor.