Are you are thinking about building a house extension in the Edinburgh area?

If so, you will no doubt want to know the answer to these 4 questions!

  • Step 1: How much does it cost to build a house extension in Edinburgh?
  • Step 2: How do I start the process?
  • Step 3: What Local Authority permission do I require?
  • Step 4: How do I find a builder to build my extension in Edinburgh?

At John Webster Architecture most of our customers have never built a house extension before and don’t have an in-depth knowledge of the construction process, but that’s OK that’s what we are here for 😊.

Contact me directly to speak about your Extension project john@jwarch.co.uk

It’s important to find out the answers to these questions BEFORE you start the process. Before you dive straight in and hire an Architect, do your homework. You will want to know as much as possible about the entire process before you are committed to paying for expensive design drawings.

We want to let our customers know how much everything will cost (including the hidden costs) and give them information on all the other ‘stuff’ too. We have produced this guide as an ‘Ultimate guide to building a house extension in Edinburgh’. It will take you from where you are now (the very beginning) all the way through to ‘handing the keys over’…we won’t only tell you the good stuff, we will tell you the ugly stuff too.

So, let’s dive in and get started.

Edinburgh Architects

Do you and your family love where you live but require a bit more space….Building an Extension could be the Perfect Solution


Step 1: The Cost of Building an Extension

How much does it cost to build a house extension in Edinburgh?

Well, it depends!

How long is a piece of string?…..not a great start but I promise you it gets better!

It depends on a lot of things, there are so many variables it’s unreal. A lot of Architects and Builders in Edinburgh go by a simple method of calculating the cost per m2, in 2021 the cost of building a house extension in Edinburgh is £2500.00 per m2. We still hear a figure of £1000m2, 10 years ago this was a good guide, but not anymore, it’s important to be realistic. This is for a standard finish. (not super basic and not high end, but generally a good standard)

What does £2500.00 per m2 get you?

It will get you a standard finish, generally to match the standard of finish to the existing property. This is based on a standard method of construction. For example, the cost of building a 5m x 5m extension (25m2 extension say to the kitchen, and assuming it’s not a complex design) will cost £62,500.00 plus VAT

What does it include?

  • Painted Plasterboard finish
  • Complete with skirting’s and Door facings
  • Doors
  • Chipboard or concrete floor
  • Light switches and light fittings
  • The cost of fitting a kitchen or bathroom
  • A completed building ready to move into

What does it not include?

  • The cost of purchasing a kitchen or bathrooms
  • Finished flooring (carpets, hardwood floor, etc)
  • No fancy Coving or plaster cornice
  • Timber/Aluminium clad windows or bi-fold doors (these can be 4x the cost of regular windows)

If you wanted to go for a higher-end finish perhaps with a higher ceiling height or high spec glazing and high spec fixtures and fittings then the will cost more than £2500.00 per m2, it is likely to cost upwards of £3000.00 per m2

At John Webster architecture we are finding this to be a reliable guide to the cost of building a house extension in Edinburgh in 2021. It’s important to understand the costs of building a house extension in and around Edinburgh know the answer before starting as a half-built extension is no good to anyone.

Contact me directly to speak about your Extension project john@jwarch.co.uk

So, that’s the construction cost but on top of that are costs for:

  • Local Authority fees (Planning application and Building Warrant application fees)
  • Professional fees (Architect and Structural Engineer fees)

We will look at a real-life case study later in this article to understand all the costs involved…stay tuned.

Building a house extension is easy for us…we do it all the time, but for our clients, it might be a once in a lifetime experience so understandably it can seem confusing. We have written this guide as a step by step guide to building an extension.

Residential Architecture in Edinburgh

Installing a Metal Beam for Extension


Step 2: Getting Started

Time to start doing your research, this is when you look on Pinterest and start getting some ideas and inspiration for what you want, it’s a great tool for this. Homebuilding shows can be a great idea too. Set your budget, be realistic, and try to understand what you will get for your money. Write up a basic brief, list your priorities, what the number one thing you want out of this house extension project?

Set a realistic timescale, (it will take a minimum of 6 months to get the necessary permissions to build). Give yourself plenty of time, its really important not to rush. Once you have done all of this you are off to a great start, it’s time to start in earnest. Reach out to an Architecture firm that specializes in house extensions or residential architecture. It makes sense as they will be familiar with the latest domestic building regulations and probably be a good contact for sourcing a good builder

This step involves appointing an Architect or Designer to help steer you through the process of building an extension.

At John Webster architecture we specialize in residential architecture for small to medium projects.

Contact me at john@jwarch.co.uk to ask a question.

Once you have an Architect or Designer on board and have explained your brief you are off the blocks! It’s is likely that you will require both Planning permission and a Building warrant for your home extension.

Designing your House Extension in Edinburgh

Before you rush into submitting a Planning application there is the small matter of designing your extension😊

At John Webster Architecture we take our time and do this in conjunction with you the customer. We have taken the time to study the brief and understand what your main priorities are (as well as a good understanding of the budget)

Top tip:

If your Architect fails to mention the budget this is a red flag and is likely to design something that you cannot afford to build, its incredibly important to talk about this early on…at the very start of the project.

You want to start with the budget and design a house extension that is in line with this, not the other way around (design something amazing and hope for the best that it comes in on budget). This is the single biggest reason projects fail to get off the ground. Once you have worked through the design and you have a scheme that you are happy with the next step is to submit a Planning application

Side note:

At John Webster architecture we understand the process is an evolution (our first go is rarely if ever the final result). We continue to bat the drawings back and forth (with no limit) to develop the design keeping the client fully involved, after all, it’s your house!

Contact me directly to speak about your Extension project john@jwarch.co.uk

House Extension ARCHITECT in Edinburgh

Exterior Of Modern House With Extension At Night


Step 3: What Local Authority permission do I require?

Planning Permission

Do I need Planning permission to build a house extension in Edinburgh?

Most probably, yes. In some cases, though you might not, there is something called permitted development (which means you can build a limited number of projects that are exempt from planning subject to fulfilling certain conditions)

You can read all about permitted development here.

At John Webster architecture we always suggest to our clients to go with either option below:

  1. Submit a Planning application, this costs £202.00. if the house extension does not require planning approval the fee will be returned with a letter stating that in the Councils view the development falls under permitted development.
  2. Submit a ‘certificate of lawfulness’ application, this costs £101.00. This type of application is generally submitted if it is felt that the development falls under permitted development.

You can read all about Certificate of lawfulness here in a handy short guide published by West Lothian Council


These 2 options future proof you….when you come to sell your house there will be no doubt.

You have demonstrated that you followed procedure and can prove that the development is Lawful, doing nothing is not an option we consider at John Webster Architecture, even if a development falls under permitted development, you will be asked (at point of sale) for evidence of this. Trust us, it’s a major pain in the backside trying to get this retrospectively and we have seen house sales falling apart because of this.

Contact me directly to speak to me about your Extension project john@jwarch.co.uk

Once the Planning application is submitted to the City of Edinburgh Council planning department, it will be assessed by the Planners and a decision is usually determined within 8 weeks. A certificate of Lawfulness application also takes around 8 weeks to determine. These timescales are targets that are set by the Scottish government.

If you would like to read more about the Planning system and understand the basis that Planning officers make their decisions you can read about it here:

Once Planning has been secured you can safely move on to the next stage. If you are in a real hurry and are prepared to take a small risk (the risk being that Planning is not granted) then you can move to the next stage while the planning application is being determined.

The next stage is a Building warrant application.

Do I need a Building Warrant to build a house extension in Edinburgh?

Most definitely.

Nearly all building projects in Scotland require a Building Warrant. A building warrant application covers all the technical aspects of a construction project.

For example:

  • Structure
  • Fire
  • Environment
  • Safety
  • Noise
  • Energy
  • Sustainability

At John Webster Architecture we submit a Building warrant application for your home extension to the City of Edinburgh Council (Building standards department).

Contact me directly to speak to me about your Extension project john@jwarch.co.uk

In 2021 this is done digitally

You can read in much more detail about Planning applications and Building warrant applications here

Your Building warrant will be assessed for compliance against current building regulations, this is normally carried out within 20 working days (1 month), if the application fails to meet the regulations or if further information is requested then the Building standards officer will write to your Architect to inform them.

Your Architect will then revise the drawings and specification and resubmit the application, this process will continue until the Building Standards officer is satisfied the application complies with the regulations. This is perfectly normal procedure and is nothing to worry about.

You can click here to read the current Building standards


Be warned it’s a hefty document and may be quite a tedious read😊

Building warrant fees are payable by you (the client) directly to the Council and are set by the Scottish government, these fees are directly related to the cost of the building works.

Find out how much your building warrant fee might be here

So, once the APPROVED Building warrant has been issued you are legally free to start building, excellent! The next move will be to find a builder to build your house extension in Edinburgh.

You have 2 choices with this:

  1. Go it alone and find a builder, asking friends and family for a recommendation (recommended builders are normally a good bet)
  2. Ask your Architect to assist with this phase, they should be able to help you with this, it will cost more but generally well worth it!
Bathroom Extension Edinburgh

Picture of wooden details in luxury bathroom

Contact me directly to speak about your Extension project john@jwarch.co.uk

Step 4: How do I find a builder to build my extension in Edinburgh?

As we have touched on briefly a builder needs to be found