UK Architect

How Much Does a House Extension Cost in Manchester

Make your estimations accurate. Here we'll show you the key factors when it comes to the cost of a house extension in Manchester.

Corner bifold house extension
Credit: @Resi

Calculating the cost of an extension to a building isn't always as clear cut as it is for say a completely new building on a flat site. The condition, size and shape of the existing building adds an additional item of complexity, couple this with the fact that these extensions are normally on denser, harder to reach sites. 

Below we've broken down the general rule of thumb costs, as well as the items which make the most difference to the cost as a total. 

How much does each type of house extension cost?

Starting from the larger moves and working our way down to the smaller ones, Understanding the costs of each major type of extension will help clarify whether a certain extension type will be the best choice for you. 

Generally speaking across the UK and in Manchester, there are xx extensions which are most popular:

1. Single and double storey rear extensions. 
2. Single and double storey side extensions.
3. Wrap around extension.
4. Roof extension or dormer roof extension.

Image credit: @blinkarchitecture

Glass doors modern house extension

How much does a single or double storey rear extension cost?

By far the most common type of extension work across the UK and Manchester, a rear extension normally provides the most useful practical space for a property which uses the empty space of a back garden. 

Generally speaking, the cost of these rear extensions will ranges from £1,800 - £2,500 per square meter. the exact number will be lower or higher depending on structural changes and cost of glazing and fittings (for instance, an expensive bifold door instead of a regular external door).

You can use the calculator below this paragraph to make a useful estimation for your plans. Generally speaking - normal single storey rear extensions will cost between £30,000 - £45,000. Regular double storey rear extensions will cost £60,000 - £75,000.

These figures are for the construction cost, bare in mind also the cost of an Architect, Structural Engineer, Building Control Officer and application fees such as a planning application. A general rule of thumb for this is 10%.

Image credit: @A9architecture

Fully glass modern house extension

Home Extension Construction Calculator

  • Construction Cost incl. VAT
  • VAT 20% Excluding VAT
  • Professional Fees Based on average complexity
  • Initial Consultation

What is the cost of a single or double storey side extension?

Single and double storey side extensions will be specific to your property. Normally these will only be available to semi-detached and detached properties. 

On the whole, side extensions will have less large openings and simpler construction on the whole, therefore you can assume an estimation range of £1,700 - £2,200 per square meter.

This is mainly due to side extension designs being for enclosed rooms to match the existing house and less structural work to the existing house.

This means that a single storey side extension can cost between £30,000 - £40,000. This can be significantly lower if the extension is using an existing garage. Double storey side extensions will cost £55,000 - £65,000 for construction.

Professional fees will obviously need to be considered again at an estimation rate of 10%.

Concrete modern house

How much does a wrap around extension cost?

There is more room for a wrap around extension to inflate the budget.

This is because it can be tempting to make even larger changes to the existing structure of your house in order to connect certain rooms and to really get the most out of this type of project.

For wrap around extensions an estimation from £1,800 - £2,800 per square meter is a good margin. The bracket is higher here to allow for these expensive decisions, however it can still work out the same price - or cheaper - per square meter if this is consider within the design and at an early stage..

Wrap around extension at a single storey can cost between £50,000 - £75,000 for construction costs when forming an L-shape on the side and rear, however this is an area when the size and shape of your existing property will play a large part on the feasibility and cost of the project.

Image credit: @alezarchitects

Large house extension architect

What does it cost to build a roof dormer?

Another of the more popular extensions is a roof extension, normally including a dormer inside the roof. 

First of all, roof dormers will be specific to your roof / attic space and whether you have enough head height in the pitch of the roof. If - when you are inside the attic - the head height at the pitch of the roof is below 2.2m you should consider alternatives.

Roof dormers also depend on the layout of your staircase and landing within your property, this will be the most difficult item to position within your design layout. 

As you can imagine with this information, it depends heavily on your property, its size and shape. However, if a roof dormer suited to your property, you can expect to pay £1,700 - £2,500 per square meter with the average cost of a dormer coming in at about £35,000. 

We have another calculator for you below to plan ahead and get a feel for the spend.

Image credit: @CAN

Unique house extension modern

Roof Dormer Construction Calculator

  • Construction Cost incl. VAT
  • VAT 20% Excluding VAT
  • Professional Fees Based on average complexity
  • Initial Consultation

What things make a house extension expensive?

So now that we have talked about the main types, your probably wondering how you can get closer to the lower margin of the figures provided.

Generally speaking the following will allow you to make major savings. Just be aware that if you are planning to to make cost savings not to remove the entire reason of building the extension in the first place. Value engineering should be about creating as much value from your project for each pound you spend. 

Cost saving item 1

Reduce major structural works

These are normally steel beams and underpinning and are the largest changeable cost on an extension project. Be conscious of which walls are loadbearing and which are not and try to plan your openings around these. 

Cost saving item 2

Expensive fittings and fixtures

Whether its an expensive designer kitchen or lamp shades. It may be tempting to buy all of these items and populate them around your new extension immediately, however these price tags can quickly add up. Key design features can be added after the project is finished and within moderation.

Cost saving item 3

Not using standard construction techniques

This isn't necessarily a bad thing, design and innovation is fantastic. But if you are looking to make savings, it can be a good idea to see where these may not be having as much impact and giving you the value you are looking for. 

This is again a practice of moderation over excess.

How do I make my house extension as cheap as possible?

If you are looking to go the extra mile to make your extension as cheap as it possibly can be, that doesn't necessarily mean you have to compromise on the final product.

The tips below are based more on the 'process' of the construction rather than what is included within it. These options require a lot more effort and labour but will reduce your your construction costs significantly.

DIY Option 1

Get the building shell built and do the rest

A popular option for anyone without too much specialist trade skills. If you have your builder construction only the large items - the foundations, walls, roof, windows and doors - you can do the interior floor, plastering and garden landscaping yourself.

This means you do not have to get involved with the messy hard work of pouring concrete and wet trades, which will be under heavier scrutiny by a building control officer. The cost savings will be much larger however where you are taking on a large portion of work yourself. 

DIY Option 2

Build your extension yourself

This option is for people with the time on their hands and lots of trade experience. It is also heavily recommended that you inform your Architect so that they can design according to your needs. 

This option requires the most rigor and time, however it will open up options for amazing design choices while cutting your construction costs by up to as much as 50%!

DIY Option 3

Looking into 'flat pack' building methods

While you are looking at self build, it may make sense to look at prefabricated designs and options which make the build on-site quick and easy. For many people this provides the perfect blend or cost-saving, speed and ease.

Many Architects provide expertise on CLT self build projects, if you would like to explore this further, we offer free consultations on many alternative building methods.


Across the most popular options available for house extension work, the costs you can expect will be similar. When making cost-savings, be sure to look out for ways to simplify and even carry out the work yourself in order to keep you extension project on time and on budget.

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