What is the process for building an extension? This article looks at the process for building an extension and where to start with the building project.

Building an extension on a house – where to start

Planning and building a home extension project can be a big task, even for small extension projects, yet the result is often worth the difficulties. You can increase your already beloved space with an extension without having to move your belongings and deal with hefty moving fees. You can build a home extension to support a number of lifestyle changes, from a growing family to a new entrepreneur in need of home office space.

The addition of an extension not only increases the space in the home, but it can add value to the house for when you decide to sell. Value-added can be determined by the type of extension built and the best-selling features in the local area. Before choosing the type of extension, consider the fact that some are feasible under your 'Permitted Development Rights.

This means planning permission is not required, reducing timescales and reducing costs for the project. Further comprehensive information regarding these rights can be found online with the UK Government's official guide: 'Permitted Development Right for Householders Techincal Guidance'.

An example would be Loft Conversions; this type of home improvement generally doesn't require any planning permissions, unless the height or width of the loft is extended further than the original roof outline.  However, we offer a condensed and equally informative list below, as the official guide is quite lengthy. Below we discuss which extensions fall under this category and the conditions. 

HOW MUCH WOULD IT COST TO BUILD AN EXTENSION

What size extension can I build without planning permission?

Single-storey rear extension 

Under your right for Permitted Development, you can add a single-storey extension to the rear of your home under two specific circumstances;

• Height must not exceed 4m
• The width must not exceed 4m (detached) from the original rear wall, or 3m (non-detached, terraced)

Moreover, if the new extension is being added to an existing extension, then the above measurement guidelines should include both the old and new builds. Using the 'Neighbour Consultation Scheme,' you can even push these limits further with non-detached houses allowing 6m width from original build and detached houses allowing 8m. This scheme means planning permission isn't required.

Instead, it allows you to make a proposal and give your neighbours 21 days to object to the idea, with valid reasoning to support them. Once this period is over, the Local Planning Authority will have another 21 days to grant approval and request a fee for a Lawful Development Certificate; this proves you don't need planning permission and your Permitted Development is legal. 

Two-storey rear extension  

Similarly, you can build a two-storey rear extension without planning permission, as long as it meets the following requirements;

• Height must not exceed 4m
• Distance from the rear wall must be no more than 3m
• Should be within 7m from the boundary of your plot that's directly opposite that wall
  

Be cautious that adding another storey on top of an existing single-storey extension when the original build extends by more than 3m beyond the rear wall will require planning permissions. It will not be legal under your permitted development rights, so always check before planning begins. 

Side extension

A side extension can be built without planning permission if its width is no more than half of the width of the original house, single-storey and no higher than 4m. If the new extension is an add-on to a previous extension, then the above measurements apply to them both together. If the side extension is built to pass beyond the rear wall, whether or not it's attached to the wall, then it is subject to the same rules. 

• Height must not exceed 4m (one-storey)
• The width cannot exceed half of the width of the original house 
  

Rules may vary depending on the location; for instance, in Wales, a two-storey side extension may be possible under a Permitted Development application.

Rear-plus-side extension

If you want the extension to extend the rear and side walls, the restrictions become slightly more confusing. Ensure your design fits into requirements before any further steps are taken.

• Height must not exceed 4m (one-storey)
• No more than 6m past the rear wall (terraced, non-detached) or 8m (detached)
• The width cannot exceed half of the width of the original house 

'Infill extensions' refer to those built in the space between the rear and side wall, often used to square off the house blueprint. This type of extension is allowed under Permitted Development Rights. You can also build two separate buildings, although wraparound designs require planning permission as they'll likely exceed width limits. 

Height limit planning rules

Height restrictions for extensions are quite straightforward. Simply put, the top height of the new extension should not exceed the height of the original home's highest roof ridge line or flat roof. The extension's height must not exceed the height of the highest roof ridge line (or flat roof) of the existing house.

Eaves are the edges of the roof that overhang the wall face to the side of the structure. Eaves are the edges of the roof which overhang the face of a wall and project beyond the side of a building. If the new extension is within 2m of the boundary line, the eaves must be no higher than 3m, according to the Permitted Development Guidelines.

To check for this, find your neighbour's closest window and draw the imaginary line to see if it will breach. This also relates to the neighbours' Right to Light', which often comes under the Prescription Act 1832, or the more recent 'Rights to Light Act 1959.

Overall, its' best to be honest with your neighbours and show them the extension designs, especially when boundaries are involved. Some disagreements may arise, but you'll have plenty of time to adjust the designs and rectify the problem before it's too late! A general rule is; that if the extension will be any higher than 7.2ft, you should speak with your neighbour; any lower, and it should be okay.

Steps To Adding An Extension To Your Home

Creating more space in your home is becoming increasingly popular as the way we use our homes evolves. We now expect our homes to provide a place to eat, relax, work out, entertain and more; as demand increases, so does the need for usable space resulting in a need for extensions. As housing prices rise and the market worsens, there is an excess of demand that cannot be met.

In this volatile housing environment, many are opting for home improvements and house extensions. It's a very smart move to increase your existing space rather than opt for the challenges of securing and financing an entirely new home. Moreover, houses can hold a lot of important memories, and with an extension, you not only get the benefits of a new space, but you get to retain the home you cherish and add resale value to the home.

Below we discuss the route you should follow to construct a successful, efficient and feasible plan for a new home extension project.