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Top 5 mistakes you must avoid when extending your home [2024 edition]

We've identified some of the most common errors people make during the designing and building of extensions - and explain how to stay on the right track

19 January 2024
3 minutes read
Modern rear kitchen extension idea with large bifold windows with transom windows, custom-fitted grey kitchen cabinets with integrated oven, dishwasher and fridge/freezer with matching kitchen island with white countertop and sink

So, you're thinking of extending your home for an extra bedroom, living space or a new kitchen but want to avoid the common home extension mistakes many homeowners make?

We are all scared of making mistakes and losing money. Generally speaking, if you make mistakes when you extend your home, it takes at least double the time, money and effort to put your project right. So what can you do about it?

You can be very careful while planning to extend your home by taking extra time to avoid hassle and getting into trouble! Here are some of the most common home extension mistakes you should avoid for your perfect home extension.

Modern rear kitchen extension idea with large bifold windows with transom windows, custom-fitted grey kitchen cabinets with integrated oven, dishwasher and fridge/freezer with matching kitchen island with white countertop and sink
House Extension by Urbanist Architecture
Rear kitchen extension ideas with a large retangular skylight shining onto the white marble kitchen island and three teal fabric bar stools leading directly onto a sunny and green garden with wooden patio furniture
House Extension by Urbanist Architecture

1) Missing the bigger picture

The point of a home extension is to create additional space for your existing home, so it is crucial you consider the entire layout of your house.

Things to consider are:

  • How will the new space improve the flow of the rest of your house? Do you have a clear idea of how the new rooms will slot in with the existing ones, and whether you need to change the layout to fit in with what you are adding? (And have you budgeted for that?)
    • Who will be using the room/space?
    • How will it add value to your property?

A badly designed extension not only won't improve your house while wasting your money, it can leave what are currently good rooms dark and unappealing.

2) Not getting planning approval

You're impatient to get your extension built, you've convinced yourself that you are entitled to build and so you push ahead without checking the regulations. What happens? Once the local authorities learn what you've done, you end up having to demolish what you've built – and to start again, you have to get permission from a council that has no reason to trust you.

Compared with the cost and time wasted that way, waiting a few months for the council to make a decision on your application suddenly isn't a big deal anymore.

Depending on the type of your extension, you'll need to make an application for planning permission or permitted development. You should do this with the guidance of a professional.

The extension types that may require planning permission or a lawful development certificate (for permitted development) include but are not limited to:

  • Basement extension
  • Rear extension
  • Side extension
  • Front extension
  • Wrap-around extension
  • Multi-storey extension
  • Roof extension
  • Additional floor extension

Even a whole new bay window counts as an extension and will need planning permission.

We'll put this bluntly: not getting the agreement of your council for you to build an extension is a gamble you can't afford to take.

3) Forgetting your neighbours

Regardless of whether you get along with them or you absolutely can't stand each other, you must always inform your neighbours about the renovation that is going to take place on your site.

You should observe the Party Wall etc. Act 1996, as failing to do so will interrupt the construction process and create unnecessary headaches. The agreement with your neighbours usually takes place in letter form, and could also be done by a third party such as a party wall surveyor.

4) Hiring shady builders

So, your local authority grants permission, your neighbours are informed and you have found builders who are willing to work immediately. Perfect! The construction begins and it all seems to go smoothly until completion. Suddenly your property is in great danger with leaks, cracks and builders out of sight!

But this doesn't have to happen. To avoid the nightmare of falling under the spell of cowboy builders, do your research properly and always be suspicious. Ask builders for references and speak to their past clients. Ask to see their previous work to get an idea of their competence.

Or even better, you can appoint your architect to be your Contract Administator and Project Manager to avoid disappointment.

5) Picking the wrong materials

The choice of materials is crucial. Firstly, if you are using permitted development, they have to match the existing house.

If you are getting planning permission, you have more flexibility. But the external appearance of your extension should be sympathetic to the existing look of your house and neighbouring properties, particularly if you decide on a side extension.

Local authorities also focus on the impact your renovation will have on the overall feel of your street. Being selective and getting professional advice is extremely important. You will be glad you did.

Think seriously about the long-term – cheaper materials might look OK for a year or two but will often look terrible in 10 years. And with extensions these days often costing above £100,000 or more, building something that will last less than a decade in good condition is a terrible move.

Using shoddy materials for your extension can also end up causing damage to the rest of your house. In short, trying to save a few thousand pounds right now could end up costing you tens of thousands down the line.

Work with the best architects and builders to avoid costly mistakes and save hours of frustration

Your project's success is 100% dependent on the quality of professionals and tradespeople you employ. Don't waste your money and time on people that do a bad job!

How Urbanist Architecture can help you 

Urbanist Architecture is a London-based RIBA chartered architecture and planning practice with offices in Greenwich and Belgravia. With a dedicated focus in proven design and planning strategies, and expertise in residential extensions, conversions and new build homes, we help homeowners to create somewhere they enjoy living in.

If you would like us to help you with your extension, please don’t hesitate to get in touch.

Selena Martin, Architectural Designer at Urbanist Architecture
AUTHOR

Selena Martin

Selena is a pivotal member of our architectural team, with extensive experience in new build design, renovations and refurbishments. Selena approaches every project with enthusiasm and thrives in providing clever design solutions to tricky sites.

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