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How Much Does an Extension Cost in Scotland in 2024?

Our comprehensive guide contains up-to-date figures to help calculate your extension project, plus important factors to consider.

A timber frame sits on the ground at a new build construction site. Grass and daises surround the timber.

If you're craving extra space in your home, but don't want the hassle and expense of moving, then a building extension could be the answer.

But how much does an extension cost? Unfortunately, that's a bit like asking how much a car costs - there is no simple answer. A Ford and a Ferrari will both get you from A to B, but one is priced much higher than the other. The same principle applies to building an extension. There are so many variables which impact price, that it’s impossible to create a blueprint which will apply to every project.

However, you can estimate the average price of your extension using cost per square metre (£/m²). If you don't yet have construction drawings, the cost per square metre build rate is a rough guide of what you can expect to pay. We’ll take a closer look at cost per square metre later on. Firstly, let’s consider the major factors which influence an extension’s price.

Size, Shape, Height & Extension Type

There are many different types of extension to add space to your original house, including:

  • Single storey extension
  • Multi-storey extension
  • Semi-detached extension
  • Kitchen extension
  • Bathroom extension
  • Garage conversion
  • Conservatory extension
  • Loft conversion
  • Basement extension

The biggest impact on price is how the space will be used. For example, a kitchen or bathroom extension will cost more than a small office or playroom extension. Typically, the larger you go with size, shape and storey height, the more you can expect to pay.


Finishes and Specification

The quality of materials you finish your extension with (the specification) will also play into your final cost.

Think of this as you would the star rating of a hotel. A standard-spec finish (3 stars) with off-the-shelf laminate flooring, basic quality MDF skirting boards and window sills, and standard lighting fixtures are cost effective options.

High-spec luxurious finishes (5 stars), such as solid wooden flooring, natural stone tiles and custom-built cabinetry and internal doors will add a unique look to your home, but also increase the cost.


Type of Construction

The construction method will also influence cost. A simple timber frame extension will be more economical than a complex steel frame addition. Similarly, the type of building materials used in the external finish – timber cladding, glass, metal, stonework – will all vary in price. Changes to steelwork or walls in your original home will see extra costs.


Windows and Doors

If you choose triple glazing, window seats or bifold doors, then you’ll have to budget more than standard, off-the-shelf windows and doors. The type of materials will also affect price. For example, uPVC is more affordable than aluminium or timber.


Kitchen and Bathrooms

For a bathroom, allow an additional £5000. But remember, this price will vary widely depending on the sanitaryware you choose. For kitchens, £10,000 will get you a low to mid-range suite. Bespoke kitchens will cost more.


Demolition and Waste Removal

Will an existing extension or structure need to be demolished before your new extension can be built? This will need to be factored into the cost, along with skip hire and removing waste from the site. If asbestos is present, a specialist contractor will be required to remove this safely. Another important factor to consider is the ease of access to the site. This can add to the costs of transportation of materials, tools and equipment in and out of your property.



Preparing the site, digging foundations and underpinning (strengthening the foundation of an original building) are important works which ensure the structural integrity of your new extension. If your site has sloping ground, expect prices to be higher than if you were building on existing flat terrain. There can also be additional costs depending on whether you're moving drainage, pipework or trees.

A builder kneels on the ground, next to a group of windows which are about to be installed. He holds and reads big, white plans.
Close up of timber supports screwed into new Nordan windows. The windows are due to be installed in a new build home.

House Extension Cost Per Square Metre

Building cost per square metre (£/m²) is a useful method to calculate a ballpark price of an extension, with m² being the total internal floor area of your proposed living space.

Whilst we consider these rates below, we would always advise consulting a professional builder and investing in the initial plans for your extension to ensure it's designed at a price that's affordable for you.

Based on our own recent domestic projects in Scotland, we know that in 2024 the construction cost of extending and refurbishing a home falls between the range of: £2500 - £3000 per metre square + VAT.

What Does This Cost Include?

This cost is for building the shell of the extension only and excludes fitted joinery, kitchens and sanitaryware, as these all vary widely in price.

As every building project is unique, this price range should be used as a guide only. Coldwells Build cannot provide an accurate quote without detailed plans from your architect.

Other Costs to Consider

  • Surveyor fees: necessary if a survey of the existing house is required
  • Design team fees, ie - architect
  • Structural engineer fees
  • Quantity surveyor
  • Planning application fee to local authority: planning permission is required, if your extension doesn't fall within permitted development rights
  • Building warrant fee to local authority: this fee varies based on estimated construction cost
  • Landscaping
  • VAT at 20% of the labour, materials and services
  • Temporary accommodation: you may need to move out of your home for part of the build
  • Storage for goods and furniture
  • Insurance: check with your home insurance provider there are no additional costs for insuring your home for a construction project
Close up shot of a circular saw cutting through timber. Sawdust is flying through the air.

How to Make the Most of Your Extension Budget

Opportunities to save money include:

  • Re-using and recycling existing materials
  • Use off-the-shelf products rather than designing bespoke items
  • If possible, time your extension for good weather. Bad weather can mean delayed schedules and if you're renting while you extend, increased rental costs, too.
  • Be economical with cladding or render, but spend well on the main structure of the extension, including walls, roof, windows and insulation. Whether you're building a glass extension or a double storey extension, cutting costs with poor materials will only cause more problems down the line.
  • If there’s something specific you want to include in your extension, but your budget won't stretch, speak to your builder. They can utilise their experience and existing connections to investigate suitable alternatives.

Budget Advice From Professionals

As we've learned, there are many factors which influence the cost of an extension, so it's crucial to establish your budget upfront and stick to it.

To achieve this, we recommend you work with an architect who has a track record of collaborating with builders in the design stage to provide cost visibility from the start.

This simple but fundamental difference saves money and time by transforming the relationship between builders and architects into an alliance which fosters not only creative collaboration, but most importantly, budget control.

The architect manages the creative design, and the builder and architect work together on construction science and costs. When construction costs are monitored and tracked in the design phase, the risk of budget blowouts decreases.

It’s also an opportunity to identify any construction related challenges early on. With practical input from the builder, potential issues can be ‘designed out’ before leaving the architect’s desk, saving time on rework at a later (and more costly) stage.

We always recommend you discuss your budget with your builder, as they can guide you on what type, size and spec of extension it will allow for.

Final Thoughts

Extensions can be complex projects, but with careful planning, they're the most rewarding home improvements you can make. 

If you’re in the process of planning your house extension and could benefit from some real-world professional advice about budget, logistics, timing or any other elements, then please get in touch to schedule a complimentary planning session.

Read Time: 5 minutes Type: Custom Build, Advice, Renovation - Author: Clare Booth, Director Share:

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A room inside a modern house. Floor to ceiling glazing takes up one wall. The floor is micro cement. A white table is in the centre of the room. Timber chairs surround it. A tall plant sits in a pot in the corner of the room.