Extensions
Unlike loft conversions, house extensions are more about creating space than adding value to the property, although it is of course an important consideration. Extending your home may be a more affordable option than moving into a bigger one, especially if the difference in house price to the next size up is considerable.
Whether a house extension is possible is inevitably dependent on your ownership of the land on which you wish to build, and on whether your plans are passed by Planning Permission and Building Regulations.
Extending your home can be quite stressful; rendering some areas of the property ‘no go’ and creating an unavoidable mess for a time. However, compared to moving house it will usually be less hassle.
Costs:
Before any work on your proposed extension has begun, there are prior costs to consider. An architect will be required to draw up the plans, and you will have to pay two fees to the council for Planning Permission and Building Regulations approval.
Depending on the size and type of your extension, costs in the design will vary considerably. If you need to knock down an exterior wall to extend the property you will require a structural engineer to calculate the size of RSJ, which is the beam to be supporting the wall across the new gap. A quantity surveyor is needed to work out the cost of the beam itself.
You builder will quote for what he can see, but plans may be forced to change when things occur or are discovered after the work has begun. It is advisable to set aside some emergency funds in case extra costs emerge.
Planning:
In order to have your Planning Permission and Building Regulations approval granted, your extension should blend into the existing property and the surrounding neighbourhood. Similar materials should be used where possible, and the design should be kept to the same scale and character. Any additional details like decorative effects or windows should also reflect the existing nature of the property. It is important that the extension does not overtake the property and dominate its appearance.
Nor should the proposed extension affect any neighbouring properties. It should not reduce your neighbour’s privacy or daylight, and should not obstruct or dominate their view.
If it is inevitable that your extension will overlook theirs, in the case of terrace houses, the windows should be at least 22 metres apart and can have frosted glass to prevent loss of privacy. A wall or fence to obstruct the view can also be erected, or you can install high windows or roof lights.
If the extension is at the rear of the property, it should not interfere with neighbouring properties whether by blocking light or view, evading their privacy or even by physically altering their property. This also applies to conservatories.
Extensions at the front of the property are rarely allowed as they will inevitably affect the overall appearance of the street or neighbourhood. If a front extension is to meet approval, it must stringently adhere to the original design and form of the property and neighbourhood dwellings.
Considering the exterior of the property; an extension should not be created if it will reduce the number of parking spaces and thus cause problems with road traffic or safety.
Any trees around the property should be left alone and remain unaffected by your development plans where possible.
The 45º Test:
According to the Building Research Establishment guidance which is endorsed by Councils, site design for a house extension should pass the 45º test when considering daylight access for neighbouring properties.
Taking your house plans, draw a diagonal line at 45º from the highest corner point of the wall where your neighbour’s window is located. Then draw another line at 45º from this plan toward the window wall at the end of the extension.
If the middle of this main window on the neighbour’s house lies on the extension side of both these 45º lines, the extension may obstruct light into the window.
The test however, is just a measure of guidance and does not result on definite approval or denial.