Tips and advice for a property extension

Tips and advice for a property extension
May 31, 2016 Rosie Williams
tips and advice for a property extension project

Due to rising house prices, extensions are a realistic way for property owners to create more space and add value without needing to sell and move home. Whilst extensions are not often cheap, they can add value to your home if planned well and serve a purpose for anyone needing to stay in their home for the next few years but need a little extra space.

Extensions do require some significant planning and project management to avoid problems in the future and there are a lot of factors to take into consideration before embarking on an extension project.

Design and planning phase

Probably the most important part of the extension process is in the initial design idea. With the right design and research, the rest of the planning process should be a smoother process.

You need to make sure that the extension will actually add value to the property, otherwise it can become an expensive project without any financial return. You can get advice from architects or estate agents to get an idea of what sort of financial return might be possible from your plans.

During the design phase, it is important to consider the look and feel of the property and how the extension may impact this. Try to match the existing property features, such as the roof, windows & doors and be sympathetic to your surroundings.

Talk to your neighbours

The neighbours can have a significant impact on the extension plan if they oppose any part of the planning application. It’s a good idea to get them involved as early on as possible to gain buy-in and try to foresee any potential oppositions which could delay you later down the line.

Get a good Architect

You’ll need an architect for the detailed specification as a very minimum, although they can also be very useful for obtaining advice on the extension plans, issues regarding planning permission and any local factors which may impact the modifications. At an extra cost, architects can also oversee the extension project which could be suited to someone with little experience or time to dedicate.

Permissions & applications

For most properties, obtaining planning permission will be necessary before any building work can commence. Planning is there to control how neighbourhoods are developed, focusing on land use, the appearance of buildings, landscaping considerations, road access and any environmental impacts. You will certainly need planning permission in the following circumstances:

  • The proposed extension is higher than your original roof.
  • The proposed extension is over four metres high at any point and within two metres of the property boundaries.
  • The total volume of the original property is more than 115 cubic metres.
  • The total volume of the property is increased by more than 10% for terraced houses.
  • Any proposed extensions in conservation areas, national parks or the Broads.

Gaining planning permission

You will need to submit an application for planning permission with your local council. The proposed extension plans will be put on the Planning Register once received by the council for public viewing and neighbours will be notified. The proposed plans will then go into consultation, giving people the opportunity to leave comments or opposition. Without any opposition, planning permission is normally obtained within 8 weeks, although 26 weeks is the statutory maximum.

If planning permission is refused, amended plans can be resubmitted within 12 months without any further charges. Anyone who builds an extension before obtaining planning permission can face extensive fines or even be required by law to demolish the new building work.

Building Regulations

In the majority of cases, it is necessary when extending a building to ensure it complies with the Government’s Building Regulations. These are a set of minimum standards for the design and construction of building to ensure they comply with health and safety rules.

A decent builder should be able to help you to ensure the extension meets all of the Building Regulations, also making sure all necessary inspections are completed.

This is a separate process from planning permission and the architects detailed plans must be submitted to the local planning authority as early as possible. Building control surveyors will examine the plans before approving the project. Your builders must notify the council before any work commences and inspections can be made throughout the project to ensure the work complies with Building Regulations.

Labour and supplies

Choosing a building workforce can be a very daunting part of the process, making sure you choose a reputable builder and avoiding the many cowboys out there. Be wary of low quotes – these are often achieved by cutting corners which could lead to poor quality work and could cost a lot more money in the long run. There are plenty of resources for finding reputable tradesmen such as the Federation of Master Builders (FMB).

The best approach is to obtain several quotes from different contractors, making sure you include building supplies into the quote. Most reputable builders will be happy for you to speak with their previous customers for testimonials.

You should ensure you have a proper contract in place with your builder and understand the terms of your agreement. Whilst it is good practice to set a projected completion date, expect to be flexible with this as it often relies upon good weather, material availability or even a change of scope.

It may be a good idea to hire a project manager if the budget allows – they would be able to manage all of your labour and supplies and will likely already have a list of reliable suppliers.


Extension projects are often subject to change and budgets are often underestimated. Adequately budgeting is very important and is simple if you are realistic with your expectations and seek reliable, trusted advice before commencing.

It is sometimes possible to budget the extension by remortgaging the property, freeing up cash to spend on the project. In this situation it is vitally important to ensure you have checked the impact of the extension on the property value and how it may impact the sale of the property.

Always remember to budget for a little extra emergency cash in case of any unforeseen problems or delays. You should consider the cost of planning permission, Building Regulation application fees, professional fees and your existing mortgage repayments. Don’t forget the consider the budget for decorating and furnishing your new space!

Here are a few tips for saving money on your extension:

  • Work with self-employed tradespeople who’s turnover is less than the VAT registration threshold and save 20% on the would-be VAT costs.
  • Project manage the build yourself and save up to 25% in added costs.
  • Do some of the work yourself – only if you won’t be compromising on quality!
  • Keep your design simple – square corners are much cheaper than rounded rooms!
  • Recycle old building materials – it’s often being given away for free!