House extensions come in all shapes and sizes – single-story, two-story, wraparound or to the side.

But, whatever house extension you’re intending to build there are a lot of things to work out and make decisions on before the project even gets going.

From the legalities and logistics to budgets and builders – it pays to know what’s what before you start your house extension. 

House extension for every budget can include building an extension over a garage that’s already there. It is more cost-effective than building a new ground-floor extension, providing the existing foundations can take the load.If you don’t have the budget to create the home extension you want, a more cost-effective way to get the rooms you need is to look at reworking the space you have. If you rarely use your garage and parking isn’t at a premium where you live, it may be worth creating another habitable room by converting your garage. A single story home extension is the perfect way to create extra living space in your home, while transforming your space to better suit your lifestyle. Whether you’re considering a side return extension or a rear extension, it’s the perfect spot for a new, open plan living, kitchen and dining area that make for perfect family spaces and, of course, are so beloved by potential future buyers.

Meeting Building Regulations

Even if your house extension can be built under Permitted Development rights and won’t need planning permission, work must get Building Regulations approval.

The Building Regulations set out minimum requirements for structural integrity, fire safety, energy efficiency, damp proofing, ventilation and other key aspects that ensure a building is safe.

Most repair work is excluded from Building Regulations, with the exceptions of replacement windows, under­­pinning and rewiring. However, apart from certain new buildings such as sheds, outbuildings and some conser­vatories, all new building work, including altera­tions, must comply with the Building Regulations.

Typical Examples of Work Needing Approval:

  1. House extensions such as for a kitchen, bedroom, lounge, etc
  2. Loft conversions
  3. Internal structural alterations, such as the removal of a load-bearing wall
  4. Installation of baths, showers, toilet which involve new drainage or waste plumbing
  5. Installation of new heating appliances

Will a House Extension Add Value?

For house extensions to make economic sense, you need to make sure the value added is greater than the cost of the project. It can be difficult to assess, but finding similar local properties and seeing how much they’ve sold for can be a useful guide.

Be mindful of the ceiling value in your area – and be prepared to adjust your plans if necessary.

How Big Should my House Extension be?

Often extenders get preoccupied with only thinking of the project in terms of square feet, not in terms of what that size is adding to the house. Bigger is not always better when it comes to house extensions, and there are often ways of creating the feeling of more space, without adding a large extension.

This is often achieved through clever design, not only of the new space, but also what is already there.

Matching Materials

If you are aiming to match your house extension to the existing property then you need to source matching materials (which is sometimes easier said than done). One mismatch can stand out like a sore thumb.

4. Choose the Right Designer

When it comes to the design of house extensions, there are a number of options you can choose from.

These include:

  • architects
  • architectural Designer
  • specialist designers
  • package build companies’ in-house design teams

Ask for recommendations from friends, family and neighbors, but also look online for practices that have designed projects similar to what you are hoping to build.

Design in Efficiency Early On

Appending a thermally-efficient extension to a poorly insulated home will not make it cheaper to run overnight and you should look to improve the efficiency of the main house while the builders are on site.

Extending Above a Single Story

While it may seem appealing to extend above a single story extension or garage, these structures may not be able to support the load.

There are options where the old structure isn’t up to scratch: underpin existing shallow foundations; strengthen or bypass the existing with a steel frame bedded in new concrete pad footings; or demolish and rebuild. The latter is often the most cost-effective option.

Planning Services

If you are extending your kitchen, you need to confirm the position of your units, cooker and white goods before work begins so that electrics, ventilation and plumbing can be planned in.

The same will apply if you’re building a two story extension and are including a new bathroom or en suite in the design.

Connecting the Old and the New

How well the additional space sits alongside the original property will undoubtedly affect the success of the project. While there are no hard and fast rules, you will need to make a decision on whether you want your new house extension to complement or contrast with the main house.


Should I be the Project Manager?

Project managing any building project requires high levels of patience, organization, problem-solving and decision-making skills. If you don’t feel confident dealing with the problems associated with a build site or have the time available, a professional PM, main contractor or package company is a must.