How much will a home extension cost me?

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How much will a home extension cost me?

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Ground Floor Extension, Drury Rd Casas de estilo clásico de London Building Renovation Clásico
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Home extension costs are definitely one of those mythical 'how long is a piece of string' questions, but there's not denying that a well thought out addition can not only significantly increase your living space, it can also add to your quality of life as well. If you've ever looked at a striking project and found yourself  wondering how much is an extension, we want to give you an idea of what you could expect to spend, right now. 

Naturally, your architect will be able to give you far more accurate costings, as and when you begin the design process, but for now, come with us and see what you should expect to face, in terms of house extension costs. We think you'll get some great ideas!

1. Single-storey small extensions.

Ground Floor Extension, Drury Rd Casas de estilo clásico de London Building Renovation Clásico
London Building Renovation

Ground Floor Extension, Drury Rd

London Building Renovation

Firstly, it's important to recognise that extensions in any built-up city will always cost more than those in rural locations. Secondly, let's focus on small one-storey additions, for a moment. While you also need to take into account design fees and any relevant taxes and permits, on average, extension costs per sqm will come in at around 2,500 SGD.

2. Two-storey extensions.

The Cube, Winchester Casas modernas de Adam Knibb Architects Moderno
Adam Knibb Architects

The Cube, Winchester

Adam Knibb Architects

With a one-storey extension ballpark figure known, it is an easy stretch to realise that two-storey extensions will usually cost around 50% more! That's just common sense mathematics. Naturally, two-storey extension costs will be more, as there will be extra structural adaptations to be made and the process will take longer.

3. Bathroom and kitchen extensions.

Bright, clean, contemporary Cocinas de estilo moderno de homify Moderno

Bright, clean, contemporary


Extensions that specifically provide space for a new kitchen or bathroom in the new room will always cost significantly more than a simple open extra room. Essentially, you'll have the building costs to think about first and then, you need to account for new sanitary items or cabinets and appliances. 

4. Consider costs of finishing touches.

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Naturally, you'll be attempting to not spend your whole budget on just the building of an extension, which is why you absolutely have to think about the finishing touches, the whole way through. A good rule of thumb is to focus on installing a few timeless and investment materials, such as granite kitchen worktops, while selecting cheaper cabinets that won;t give an overall impression of cost-effective design.

5. What is the site is difficult to build on?

Existing 1900s Family Home in Hindhead, Surrey de ArchitectureLIVE Moderno

Existing 1900s Family Home in Hindhead, Surrey


If your plot is going to be troublesome to build on, you will definitely incur extra costs during an extension project. The most expensive elements that will affect your budget include:

- Solid foundations. If you have a difficult to manage soil type, you might need to excavate using expensive machinery.

- If access to your proposed site is limited or restricted, expect your costs to spiral. 

- Propping up your existing home and supporting the structural elements will always require significant investment. Should you need to remove or adapt any windows, this will also need acrows and support systems as well.

- If any pipelines or drains need to be moved, adapted or accounted for, you might find yourself getting into some unexpected financial trouble. So plan ahead!

6. How will the area affect the cost?

Forest View Balcones y terrazas de estilo moderno de Clear Architects Moderno
Clear Architects

Forest View

Clear Architects

Now this might sound like a strange thought, but the more exclusive and beautiful your location, the more you might need in invest in an extension project, to keep up! You won't be abel to get away with a cheap or lacklustre design, as it will stand out, for all the wrong reasons.

7. Will materials play a part?

Absolutely! We have given you an estimation of building costs, but the construction materials that you select for a home extension will significantly affect the final price. Your design professionals will be able to advise you as to the best ways to capture a certain aesthetic, while staying within budget.

8. Will project management help?

Modern Garden Room Anexos de estilo moderno de ROCOCO Moderno

Modern Garden Room


In order to complete a home extension project within your budget, it makes perfect sense to ask for professional project management services to be completed. Don't simply see this as an extra cost though, as your architect, for example, can call in various deals and oversee effective timescales, which will actually save you a significant amount.

For some extra extension inspiration, take a look at this Ideabook: 7 ideas to expand your house with a small budget.

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