8 Things To Keep In Mind When Building An Extension

Building an extension to your home is a project that can provide you with that extra space you need without having to move. It can also add value to your home. However it is also a costly and potentially complex project. To make sure that you reap the rearwards of a home extension, here are 12 things you want to keep in mind.

1. Will An Extension Really Add Value To My Home?

It all depends. It is all about the right balance. If you are building an extension with the idea to sell, you want to make sure you do not invest more than what you are likely to recuperate. An extension can add value in terms of the space it will create but might not necessarily add value when selling your property. The extension you decide to build should be in line with the potential ceiling of properties in your area. That is to say that if the most expensive properties in your area are selling for £500,000, investing £300,000 in a massive extension will probably not be the best financial decision even if it provides you a great home. Talk to a local estate agent as they can help you understand the local market and give you an idea of what similar extended homes in your area are selling for.

2. Do I need Planning Permission?

You might be able to build an extension under Permitted Development. If so, you won’t have to go down the formal route. Keep in mind that if your house is in a Conservation Area or a National Park, the amount of work you will be allowed to carry out is reduced. Under Permitted Development you can carry out certain work as long as you meet criteria such as:

  • You can extend a detached property by eight metres to the rear if it is a single storey extension (six metres for a semi-detached or terraced house) or by three metres if it is a double storey.
  • A single-storey extension can’t exceed four metres in the ridge and the eaves, and the ridge heights of an extension can’t be higher than the existing property.
  • A double storey extension can’t be built within seven meters of its rear boundary.
  • A side extension can only be single storey and a width that does not exceed half the size of the original building.
  • Extensions can’t go forward of the original building line.
  • In certain areas such as those of outstanding natural beauty or conservation areas, side extensions require planning permission and all rear extensions must be single storey.
  • An extension must never cover more than half the garden.

From 31st August 2020, the rules changed so that two-storey extensions on detached, semi-detached and terraced houses will be fast-tracked as long as they get prior approval. This means the local authority have to be notified of the details before the project starts and it’s a much more involved process with the Local Authority. However, some restrictions apply.

  • Once completed, the building must not be more than 18 metres hight.
  • The floor-to-ceiling height of any additional storey must not be more than three metres in  height or higher than the floor-to-ceiling height of any of the existing storeys.
  • The overall height of the extension, including the roof, must not be more than seven metres high.

If you are planning a larger extension, chances are that you will need Planning Permission and will need to submit an application. It is a good idea to engage with your local authority early on and get information on local planning policies prior to submitting your application.

3. Do I Need A Lawful Development Certificate?

Even if you can extend your home under Planning Development (PD) rights, it is always a good idea to apply for a Lawful Development Certificate from your local authority to ensure that the work was lawful and met the PD requirements.

4. How Close To A Boundary Wall Can I Build?

If your extension requires digging or building foundations within three meters of the boundary, party wall or party wall structure, or digging foundations within six metres of a boundary, the work will require compliance with the Party Wall Act.

In some cases excavating within six metres of an adjoining property can also be covered by the Act. But this only applies where the new foundations are so deep that drawing an imaginary line downwards at a 45° angle from the bottom of the next door’s foundations would hit them, for example on a steeply sloping site or where you’re incorporating a basement. 

There are two other situations where the Party Wall Act applies. When a new extension is designed to maximise floor area by building right up to, or ‘astride’ the garden boundary between two properties and when you physically cut or alter a party wall. (such as where you want to build onto your neighbour’s existing wall so it becomes your new extension’s party wall).

5. What Do I Need To Consider When Drawing Up Plans?

When drawing plans for your extension you want to keep in mind:

  • soil type on the site
  • services
  • surrounding trees
  • any history of flooding
  • site access
  • rights of way

Also do not forget to notify you insurer as your policy might not cover you during the work period.

6. Do I Need An Architect To Build An Extension?

You do not necessarily need an architect but it can be very helpful. An architect can help you draw plans that can be used for submission to your local authorities for planning approval and to produce drawings and calculations for Building Regulation purposes. (These documents will also form part of the tender process documents when hiring builders). When choosing an architect, chose one that you feel gets your lifestyle and understands your needs.

7. Do I Need To Provide A Design Brief?

The simple answer is yes. The clearer and more detailed the better. You should tell your designer/architect/contractor how you would like your home to work for you, what your budget is and your likes and dislikes. This not only will you’re your designer/architect/contractor understand what you really want, but will let them know you are serious about the project.

8. Do I Need To Comply With Building Regulations?

Once again the answer is yes. Even if you do not require planning consent, you need to comply with building regulations. You can either submit a Full Plan Submission or a Building Notice.

  • Full Plan Submission: send plans to your local authority building control or approved inspector prior to the build for approval. The building inspector visits your site at different stages and inspects the work as it progresses.
  • Building Notice: is a statement which lets the local authority know that you will be complying with the regulations in building your extension and gives the building control department 48-hours notice of your intention to start the work. Building inspectors will inspect the work at various stages and will advise you of any problems.

Keep in mind that with a building notice, you could potentially find out that you have a compliance issue once the project has started and this means that you will have to pay to set it right. All alterations to listed buildings, including internal ones, will require consent and carrying out work without, is a criminal offence.

If you are planning to extend your home, give us a call at 020 71186155 or set up an appointment to speak with our construction experts at our office in Hammersmith. At Dominant Construction, we are always keen to talk about construction and how to make your project a success.

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