5 common home extension mistakes to avoid

Making the decision to renovate or extend your home is incredibly exciting. In most cases the results are well worth the investment, but it can be a complex process, especially for those embarking on this journey for the first time.

Here we list some of the common home extension mistakes that homeowners make, along with our advice on how to avoid them!

1 Forgetting the bigger picture

So you have plans to create a bigger kitchen….that’s just one element of your home, right?

Well it’s not quite that straightforward. Regardless of which part of your home you plan to reconfigure or extend, it’s important to consider the layout of your entire house as you plan your home improvements.

There are so many factors to consider when reconfiguring or extending:

  • How will the new space flow to existing parts of the house?
  • Will there be enough natural light to create an appealing ambience?
  • How will the needs of your family change over the next 5 – 10 years?
  • How will it add value to the property?

A badly designed extension will prove a costly mistake.

Living room internal view
Living room extension internal design

2 Poor quality drawings

Producing drawings for an extension or house build isn’t just a tick box exercise to get through the planning approval process. High quality drawings are an essential starting point for your project and will enable you to:

  • Visualise the finished project: Take away any guess work and be sure the house you are building is the house you want to live in. It can be very hard to visualise the new space and how the layout works without good drawings.
  • Gain accurate quotes: The level of detail within professional drawings is incredibly high. So when you send them out and ask a contractor to quote, you’ll receive a full breakdown for each element of the project. This eliminates any nasty surprises as you get into the build.
  • Avoid delays and confusion: Downtime on site should be avoided at all costs because it is a waste of time and money. With detailed drawings, everyone is clear about what needs to be done and when so there will be no downtime as contractors try to piece together the job.

3 Skipping the planning approval process

Whilst your extension makes perfect sense to you and your home, the council may not agree!

Although it may be tempting to push on and worry about the paperwork at a later date, you will effectively be committing a planning breach if you start work without the relevant planning approvals in place. This could lead to the council issuing an enforcement notice to restore the property to its original state, which is an extremely costly position to find yourself in.

Whether you need full planning permission or can carry out the works under permitted development will depend on what you are proposing (check out our article on types of extensions for more details click here, but even if you are going through permitted development, you still need to obtain a lawful development certificate before you can start work.

If you are confused about planning permission, and what level of approval you need, please get in touch for advice.

4 Accepting underpriced building quotes

A building quote that comes in significantly cheaper than the competitors sounds incredibly tempting, but proceed with caution.

The money you spend on contractors will take up a significant part of your budget, so it can be tempting to make savings, but if it sounds too good to be true, it probably is!

Accepting an underpriced quote can cause difficulties down the line. Maybe certain elements of the project weren’t included in the quote, or they haven’t incorporated enough labour time to get the job done with the agreed timescale. You also need to be sure that they have followed the designs that you have supplied (see point above about drawings!) and will carry out the work to a high standard.

Here at Taylor and Co Architects we provide a tender service so we can help you to manage this crucial part of the project.

5 Under budgeting

It’s important to take the time to consider your budget and how much you are going to spend on your build or renovation project. You’ll need to consider every element, including those all important finishing touches, and be realistic about what you can afford.

As a general rule, we advise clients to budget £3500/square metre of space. This figure includes heating, electrics and general finishes but excludes kitchen fittings which you should seek separate quotes for.

You’ll also need to have a contingency budget to cover any unexpected costs as they rise, which they inevitably do. So if the budget is tight, start looking at elements of the project you’d be willing to sacrifice rather than hoping it will work itself out down the line.


Although it can be tempting to press ahead and break ground, putting in the work now to plan your project and gain all the necessary approvals will save a great deal of heartache and money further down the line.

If you’d like help to design your dream home, get in touch to see how we can help.