Do I Need Planning Permission When Building an Extension? is a question we sometimes get asked at Envision CAD and there is no simple Yes or No.

Unless you live in a conservation area or one of the UK’s 15 National Parks, you may be able to extend under Permitted Development.

What is PD?

Under PD, the following rules apply:

  1. You can extend a detached property by 8m to the rear if it’s a single-storey extension, or by 3m if it’s  a double storey extension.
  2. A single-storey extension can’t be higher than 4m on the ridge and the eaves, and ridge heights of any extension can’t be higher than the existing property.
  3. Two-storey extensions must not be closer than 7m to the rear boundary
  4. Side extensions can only be single storey with a maximum height of 4m and a width no more than half of the original building
  5. Any new extension must be built in the same or similar material to the existing dwelling.
  6. Extensions must not go forward of the building line of the original dwelling.
  7. An extension must not result in more than half the garden being covered.

What may be obvious to you is that Permitted Development criteria are not very stringent.

Extending your home with a single-storey structure is permitted then in most cases, but there are some practical aspects to consider:

  • Finding an Architect or Designer
  • Building an Extension – Planning the Work
  • Who Will Manage the Work?
  • Finding a Builder
  • Tradesmen
  • Safety and Disruption on Site
  • Should You Move Out While Extending?
  • Adding Heating and Electrics When Building an Extension
  • How to Pay for Your Extension
  • VAT

Let’s look at the first point and we’ll cover the others in future posts on this website and our active social media channels.

Finding an Architect or Designer

If you look through a magazine or website or see some Grand Design on TV, you may not have the budget for these high profile architects, designers and planners. If you have the budget, you may find that the architect is not overly interested in your single storey extension. More likely is that the timescales are challenging.

We are in an age where, as consumers, we want immediate results. Need a new phone? Go online and order one. Want a birthday present delivered for tomorrow? Head to your Amazon Prime account.

Now, Envision CAD are not promising next day delivery, but what we can say is that you won’t be waiting weeks or months for a response from David Frazer at Envision CAD. It’s his company and one he wants you to be happy with and recommend to others.

You can see our Case Studies here.

If you’re planning an extension and need professional trusted advice, contact David now on: and you judge for yourself on how quickly he responds. You can also book an appointment, subject to approval by David, on our Facebook page.