8 minutes

Understanding Fees – How much will a house extension cost in London 2024?

The pandemic lead us all to spend a lot more time in our houses than ever before leading homeowners to come to the conclusion that, simply put, it was time to move out!

However, while post-lockdown property sales saw a boom, as did the number of applications on the planning portal for extension works.

As we are slowly beginning to navigate through our new sense of reality and contemplate the notion that improving is often cheaper and less stressful than upsizing, the question arises, How much will I spend on a house extension cost in London?

While there are several factors to consider when it comes to adding an extension to your property, this article aims to give you a better understanding of cost including fees for architectural designers, the various options you have when it comes to construction and the best ways to manage your budget.

To keep in mind, while living in the Capital definitely has its many benefits, construction does often come with a premium price tag in London with labour and material costs coming out more expensive in comparison to other cities.

So, what should I do before starting any works?

From the outset, consider what exactly you are looking to add in terms of space to give you a rough idea of size – the larger the extension, the higher the total build cost will be. Planning policies depending on where your property is located may also restrict the desired size of the extension. Your architectural designer will be able to look into this for you and advise accordingly.

Also, before beginning any works, consider how much in terms of a value an extension will add to the overall property and if it is expensive, will it work out cost-effective when it comes to selling?

(Please note, post-covid and post-brexit, prices have increased and building works are no exception. Therefore the below figures are to be taken as an estimate for 2021)

As an estimated figure, how much are you looking to pay?

Based on the square meterage of the proposed works, here is a rough estimate for London properties:

  • Single-storey extension: Approximately £2,000-3,000 per sqm (depending on the choice of finishes and products)
  • Two-storey extension: Approximately 2x the cost quoted for a single storey.
  • Basement extension: Due to the complexity, Approximately between £4,000 and £5,000 per square metre.

The above figures are obviously dependent on several factors (I.E) your choice of finishes and fittings and do not include both VAT and fees for professionals like your architectural designer.

Additional Fixtures and Fittings

Let’s say your single-storey rear extension will house an open plan living/kitchen/dining space. This will be more expensive than adding additional sleeping accommodation as you need to consider the specification of the kitchen including your choice of cabinets, worktop and appliances.

How much am I looking for a new kitchen or bathroom in my extension?

Again, this will depend on where you want to get your kitchen, the aesthetic you are trying to achieve and the size.

As a ballpark figure:

  • Kitchens: Typically we always say set aside £10,000-15,000 of your budget to cover a low-mid range kitchen with appliances. Again, depending on size and spec, this could go up to around £40,000 and more.
  • Bathrooms: Again, completely reliant on size and choice of fixtures and fittings but approximately set aside £5,000 to £10,000 of your budget.

Your architectural designer will be able to help you carry out some cost-saving exercises to keep you on budget. From the beginning stages, they should be able to highlight where they think most of the costs will lie in relation to your scheme.

When quotes from suppliers such as Kitchen Designers come through, they should have the ability and experience to gauge if the quote seems correct for the quality and design and where cost-saving could occur.

With the help of your architectural designer, a set of good quality detailed drawings married with several quotes from contractors and subcontractors should help you get an accurate idea of how much you are looking to spend.

Your architectural designer will reiterate this point and as we have mentioned in several of our other articles, make sure you shop around and do not always make a decision based on what is cheapest.

So, we have mentioned working with an architect or designer, you have probably begun to think,

How much are Architectural Fees?

Depending on the size of your scheme, you may only need an architectural designer. If you are looking at a slightly larger development, you may have to take on board other consultants such as Quantity Surveyors.

Architectural designers will usually price according to the total build cost, typically taking around 10-15%.

Do I need an Architectural Designer?

This is entirely your choice, however, we do believe it helps! An architectural designer not only can help you spatially plan your dream project and make it a reality, but also can assist with several other key factors such as planning, budget management and managing contractors.

Where will most of my budget typically go when building an extension?

We spoke about the costs of different kitchens and bathrooms (depending on size and spec) but other factors that do soak up the budget can include new glazing (windows and doors), site constraints, and heating.

Adding additional glazing to your property will no doubt help to create beautiful spaces, but windows and doors generally do take up a chunk of your budget. Again, size is important here as the bigger the window per sqm the more the cost will be. The type of glazing you want (i.e single, double, triple), the style and the fitting will all have an impact on cost. Doors can also be expensive, especially if you are looking to add on patio doors or bifolds. However, at CDD, we always recommend spending a little more on glazing as it can really improve your standard of living, making your home more enjoyable to live and work in (especially during today’s “work from home” culture!)

Heating the new spaces in the extension is also something to consider when it comes to thinking about adding space. Costs can be added if you need an update your boiler or add a secondary heating system to accommodate the new spaces.

Unfortunately living in London does create some sites that are more challenging than in other areas. Let’s say your property is a terraced house, builders and other contractors may factor in additional costs to cover tools, materials and access for workers. If you need to remove a tree on the site or need to move pipework or gas meters, there are again additional costs. These can be even more expensive if your property is in a conservation area or listed and may require you to use a specialist.

Use the following as a very rough guide when it comes to planning your budget:

  • The cost of builders, material and construction: 60%
  • Architectural Designer: 10% -15% of total build cost
  • Other consultants: 5%
  • Planning permission and administration: 1%
  • Party wall agreements: 3%
  • Insurance: 1%
  • VAT: 15-20%

What other costs should I consider?

Especially in London, never underestimate the cost for the planning process. The size of the extension will determine what kind of planning application you need and therefore the fee. You may also want to carry out a pre-application to discuss the scheme before submitting to the Council, which will be an additional cost to keep in mind. You will probably require building regulations approval, which is another fee to remember.

Your works may fall under Permitted Development and therefore not need to submit a planning application. However, you should still apply for the lawful development certificate to show that the works are lawful. This is approximately half the fee for a planning application.

VAT is typically 15%-20% for an extension but can be reduced if let’s say the property has not been habited for more than two years. Ask your architectural designer about VAT reductions as it is definitely a cost-saver!

Think about the cost of insurance and what will be covered by home insurer policies while works are being carried out. A lot of companies will not cover the property while there is construction going on therefore leaving you in a tricky situation if something goes wrong.

You should notify your insurers before any works on site take place and check if you need additional coverage such as non-negligence insurance to protect yourselves if any structural damage happens to a neighbouring building because of your works. Again, this will impact the budget and can be a hidden cost often overlooked.

With all of the above points considered in this article, ask yourself the questions below before proceeding with the works:

  1. What are the main aims of the project?
  2. How much realistically do I have to spend?
  3. Do I have the time to commit to this build?
  4. Will it add value to my property?
  5. Is it worth considering selling and moving home?
  6. How do I want to add space? (i.e) Do I want to dig down (basement extension)?
  7. How much space do I want to add and what will the new spaces provide? (i.e) New open plan kitchen/living/dining area, bedrooms, entertaining space?
  8. Do I have a strict timeframe in which the works need to be completed?
  9. Do I have an idea of aesthetics for the project?
  10.  Will I need planning permission and/or building regulation approval?

If you have any questions or require any help with your project please get in touch below. We are always happy to help!

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