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How much does it cost to build a wraparound extension?

Looking to find out how much a wraparound extension costs? Read our complete guide on budgeting these space-creating home projects.

5 min read

A wraparound extension, unlike a standard rear addition, utilises space to the back and side of your property. Essentially, they combine both a side and rear extension, merging them into one continuous space. They’re a great project for period properties, which typically have a lot of dead alleyway space. However, plenty of homeowners find this extension desirable as it can add a lot of space without eating up too much of your garden.

So, how much do they cost? Because of the extra structural work involved, wraparound extensions tend to be most costly than their rear and side counterparts. To discover how much you’ll need to budget, here are some rough costs to bear in mind…

How much to build a wraparound extension?

We estimate that building a 45 sqm wraparound extension could cost...

  • £75,000 to £145,000 in London
  • £60,000 to £120,00 outside of London

Try our construction cost calculator tool and get a tailored construction estimate in minutes.

Please note: the above estimates do not include VAT at 20%. They also do not include key fit-out items and assume the existing property, soil, drainage and foundations are in a good/adequate condition. It is also assumed that existing rooms affected by the extension require decoration only.

What affects the price?

How much your project will cost will depend on a variety of different factors. The main ones you’ll need to consider are…


Construction fees, along with the cost of the other professionals involved, will vary on where you are in the UK. Unsurprisingly, costs will be much higher in London, while the North and Wales tend to have the cheapest offers.


Some materials cost more than others, such as the difference between uPVC window frames and aluminium. While it can be tempting to cut costs here, we find you get better long term value by upcycling quality materials, rather than going for new but low-quality alternatives.


Individual contractors are cheaper but can be slower, as they tend to lack a lot of resources the bigger construction companies have. However, for additional knowledge, manpower and experience you will have to pay more.

Learn more about contractors and why size is important.

Design complexity

The more complex your designs, the more you’ll have to pay. Whether this is because you have a lot of structural work incorporated (such as a glass ceiling) or because you require a contractor with specialist knowledge, such as a timber expert.

To stop your costs from spiralling out of control, be upfront with your architect about your budget.

Other costs to consider

While a large part of your budget will go towards construction and the materials involved, there are still some other costs to consider.

A typical budget tends to be split like this…

Architects - 4% (based on Resi’s services)
Administration fees - 1%
Structural Engineers - 3%
Surveyors - 2%
Contractors - 30%
Materials - 20%
Fittings - 5%
Glazing - 15%
VAT – 20%


The cost of an architect will depend on their level involvement and whether or not they project manage on your behalf.

At Resi, we’re unique in that we can assist you through each step of your project, with our packages completely tailored to you.

We cover…

  • Measured surveys
  • Proposed design
  • Planning support
  • Building regulations
  • Finance
  • And introductions to local vetted contractors

It only takes two minutes to get an idea of how much your package will cost using our handy tool.

Structural engineers

Put simply, a structural engineer helps ensure your home stays standing. As their name suggests, they look after the structural calculations required for your project, which tends to be more complex for a wraparound extension than for other single-storey extensions.

A structural engineer will typically start work on your project after planning, during the building regulations stage.

They can cost anywhere between £950 to £2500.


When you start your project, you’ll require a measured survey to be carried out. This will map out your home as it stands today and forms the foundation for the rest of your project.

At Resi, we use the latest laser technology to create 3D models of your property, giving you the best start possible. Other surveyors tend to rely on a mixture of photography and manual measurements.

  • Our measured survey costs start at £250 and are included as part of our architectural services.
  • If opting for a local professional over Resi, you can expect to pay £400 to £500+, depending on your location.

Learn more about measured surveys here.

Alongside this initial survey, you may also require a CCTV drainage surveyor and a party wall surveyor. This later professional can be brought in to secure consent from your neighbours, should a shared boundary be involved.

CCTV drainage surveyor costs: £250 to £350
Party wall surveyor costs: £100 to £140 an hour


The cost of your fittings will be affected by what kind of rooms you’re looking to create. Bathrooms and kitchens will naturally cost more than more basic spaces, such as living rooms and bedrooms.

If you’re looking to get a rough cost of these rooms ahead of time, a good rule of thumb is to base your calculations on the current value of your property.

Bathrooms tend to cost 1%-4% of your home’s value and kitchens 2%-5%.

For example, a property that’s valued at £400,000 would probably pay…

  • £4,000 to 16,000 for a bathroom
  • £8,000 to £20,000 for a kitchen

Learn more: a guide to working out the total cost of your project


Good glass doesn’t come cheap, so you should bear in mind their expense during the design stage. Large expanses of glazing, such as for a glass ceiling, usually require the use of structural glazing. This will not only incur more work from your structural engineer, the cost of this glass will be more per square metre.

Learn more about the cost of glazing here.

Why should you opt for a wraparound extension?

Wraparound extensions are the ultimate way to maximise space in your home by taking advantage of dead space to the side and rear of your property (without eating into your garden). Besides the obvious advantage of having more space available, here are some other great opportunities that your wraparound extension could bring with it:

  • Extra light in the home
  • An additional room
  • A room expansion/open-plan space
  • Transforming the flow between your home and garden


While 50% of your overall budget will be spent on construction and materials, there are a lot of other costs that homeowners fail to consider.

This includes: surveying costs, structural work, glazing, architectural requirements, fittings, and that all-important VAT.

To ensure your budget ticks off all the requirements, we recommend talking to an expert for a tailored breakdown of costs. Book your free advice call here.

Not sure how much you can afford? See how much you could borrow by using our free finance calculator.

How much will it cost to build?

Which part of your property would you like to extend?

Ground Floor
First Floor


Do you need planning permission for a wraparound extension?

Wraparound extensions almost always require planning permission, but you may be covered under permitted development rights on some conditions.

What costs should you consider for a wraparound extension?

Before committing to undergoing a wraparound extension to your property you should consider these costs: alternative accommodation if you’re going to stay elsewhere, labour costs, architects, materials, structural engineers, surveyors, complexity of the project and location.

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