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House Extensions 101: Front, Side and Rear

House Extensions 101: Front, Side and Rear

Matthew Montague
4.2.2024
4 min read

Intro

There are a whole number of reasons why people extend their home. Typically its for more space, to add extra value or to change the design and usage of their property. Commonly, people extend at the front, side or rear of their property.

The front of the house is generally the most sensitive as it will affect the street scene.

Side extensions can be virtually as high as the house and the full depth without being too dominant on the street scene.

Front of House Extensions

The front of the house is generally the most sensitive as it will affect the street scene. If you look around you, the house frontage has usually been carefully designed in order to present an attractive approach. 

This is commonly known as ‘Kerb Appeal’. The rear and side of your property are generally much more simple with form following function therefore, any additions that are made might be less sensitive to design and less expensive to build. 

If space is tight, extending on the frontage can be limited as you may need to retain a minimum number of car parking spaces related to the number of bedrooms and people living in the house. We have to be very careful with hard-surfacing the frontage of houses to avoid the risk of flooding the highway with rainwater in bad weather. 

Glass Box Front Extension for Entrance Hall

Extensions: Side 

These are usually pretty straight forward. These are usually pretty straight forward. Side extensions can be virtually as high as the house and the full depth without being too dominant on the street scene. It crucially depends on the style of your house but side extensions usually look a lot better if they are slightly set back from the main house frontage. The roof height might be slightly lower than the main house, looking ‘subservient’ to the main property. The addition of a garage with a bedroom above is very common and gives your home a real asset: more bedrooms and secure off-road car parking. 

A common pitfall to consider is underground drainage at the side of houses heading for the road. If these are shared with other properties, then they might be considered public sewers and permission will be necessary to build over them. This is not unusual and there is a process to gain approval. However, think about this at the outset and establish whether this is a real constraint. 

Sometimes there can be a much larger sewer running through or a significant water main, this might be why no one has ever built in this location. In this case, you probably won’t be able to build without diverting what is below which can prove to be hugely expensive. 

You are also often in danger of overbearing your neighbours. You must consider their amenity (daylight and privacy) and be aware that if you are building near a boundary, you are likely to need to enter into a Party Wall Agreement with your neighbour. 

Finally, don’t forget you still need to access the rear of your house, usually for the use of wheelbarrows and wheelie bins which aren’t very clean when you are wheeling them through the house, so don’t cut off your rear garden entirely. 

Glass Contemporary Side Extension to Country House

Extensions: Rear

This is also very doable. Single storey extensions are not normally an issue but you must retain a certain size of garden and this very much depends on the requirements of your local authority. 

A two-storey extension is usually possible but not if it over-bears on a window next door - the 45 degree rule is a good guideline. If you imagine you are standing looking out of your neighbour’s window and then strike a line at 45 degrees to your sightline then any extension should not be seen within this line, if it is then it will be considered to be overbearing. 

Quite often in this case, you might extend fully on the ground floor but then set back the first-floor wall to avoid any issues. The issue with drainage, as described previously, still applies. This is because drains across the back of your property could be shared with neighbours and therefore considered public. 

Modern Rear Extension to London House

Matthew Montague

Award-Winning Residential Architect

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