Rear Extension
Extending a house from its rear wall towards the rear garden is generally considered a rear extension and can span one or more stories, including basement. It can be as wide as the house itself and can add significant value to a property. Rear extensions are considered permanent structures and as such are different to rear conservatories.
The Benefits
Extensions are a great way to improve and refresh your home and expand your living area without having to move to a new house. Rear extensions, in particular, are arguably the most straightforward way to achieve this.
A single-storey rear extension is a great way to enlarge a Ground Floor Kitchen or a Living room. Combined with some Internal Alterations it might also allow for a large Open Plan Kitchen/Dining/Living area, which is a preferred layout in recent years, for the many benefits of having a large open space. A Multi-Storey Rear Extension further allows for enlarging bedrooms and adding bathrooms to a home as well.
Planning
There are various rules that apply to the design of any extension, and those may vary slightly from council to council. The rules are mostly concerned with massing and appearance. Here are a few typical ones for every council in England:
The 45-degree rule
This rule has to do with preventing overshadowing neighbours and obstructing their views. In houses, it mostly applies to extensions at First Floor level and above, and it is measured in both orthogonal directions, either from the centre of the neighbours’ windows, or from the point of crossing of the boundary line and the neighbours external walls. In practice, the rule would be a major factor for determining the depth and height of a Multi-Storey Extension, while Ground Floor Extensions are typically unaffected by it.
Appearance
It is common practice for extensions to match the appearance of the original house, even more so if going through the Permitted Development route. This usually applies to the finish materials, types of windows and doors, and the roof shape. However, most councils allow more freedom when it comes to rear extensions done with a planning permission. Unlike side extensions, rear extensions can rarely be seen from the public highway, therefore, with planning permission, one can have a modern looking rear extension to their otherwise traditional house.
Overlooking
Side-facing windows, in most cases, are only allowed to be frosted and non-openable if there is potential for overlooking into your neighbours’ property. Hence, habitable rooms, like a bedroom or a living room, should ideally make use of front and rear facing windows only, which could result in limitations on things like the number of bedrooms, the living area size etc. It is common practice to either have no side-facing windows in a multi-storey rear extension, or only have them in bathrooms, hallways or storage areas.
Further Considerations
Extensions increasing the depth of a house overall, typically result in larger areas served by the same area of windows - this is commonly addressed by creating larger openings or introducing additional windows and skylights as part of the extension.
Large openings in the rear wall of the original house will require the introduction of significant structural frames, possibly driving up the cost of the alterations.
Although conservatories are different to extensions in their use and construction, in most cases the same rules would apply to their massing.
Permitted Development
Rear extensions are very often constructed under Permitted Development, as it is the more straightforward option to deal with, provided the extension complies with the following:
It matches the external finishes and appearance of the original house.
It does not extend beyond the original flank walls.
If single-storey, it is no deeper than 3m in the case of terraced and semi-detached houses, and 4m in the case of detached houses. It is possible to extend these limits to 6m and 8m respectively, subject to the neighbours consultation scheme.
If single-storey, the height of the extension must not exceed 4 meters
If single-storey and within 2 meters of the boundary, the maximum eaves height should not exceed 3 meters
If multi-storey, the maximum eaves and ridge height of extension should be no higher than existing house. If extension is within two metres of a boundary, the maximum eaves height should be no higher than three metres.
If multi storey, it must not extend beyond the rear wall of original house by more than three metres or be within seven metres of any boundary opposite the rear wall of the house.
If multi-storey – the roof pitch should match that of the existing house, as far as is practicable.
Any upper-floor window in a wall or roof slope in a side elevation must be obscure-glazed and non-openable unless the parts which can be opened are more than 1.7 metres above the floor of the room in which it is installed.
No balconies or verandas are allowed under permitted development.
The extensions footprint, combined with all other extensions and outbuildings, must not add up to more than 50% of the original garden area.
Constructing any item allowed under permitted development, does not limit your future permitted development rights, with the following exception:
If a single storey rear extension to the original house is constructed either under permitted development or with a planning permission, any upper storey rear extension will require planning permission.
It is important to remember that a wraparound extension will also require planning permission
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