Can I get a side extension on the ground floor or first floor when I live in a detached house?  

 I live in a detached house. Is there any scope in extending the side of my property on the ground floor or the first floor? 

First of all, there is a Permitted Development (PD) right to extend the sides of a property on the ground floor level, as long it’s a single dwelling (or small house in “multiple occupation” HMO) and it’s not in a conservation area, and so on.


The PD rules are quite simple:
– One must not extend a side elevation that fronts a highway, or the principal elevation, meaning that if your house is on the corner of the street, you will not be able to use this PD right.

– The size of the side extension can be only half the width of the original house, so if your house is 6 metres wide, you can extend 3 metres to the side in width.

– The maximum height of a side extension is 4 metres by the ridge (see illustration of which is the eaves and which the ridge), and no higher than the ridge of the main house. So if your house is a single-storey bungalow, you need to make sure it doesn’t go higher than the ridge.

– There is a maximum eaves height of 3 metres if it’s within 2 metres of the boundary; if it’s more than 2 metres away from the boundary you can go up to 4 metres.

– The material needs to match the existing materials, as in all PDs.

– In addition, the total area of all the extensions can’t cover more than 50% of the garden.

  A few years ago, a client called me and said that he had built an HMO in a borough where that was allowed under PD. He built side extensions and, as it was a detached house, he built them on both sides (for example, the house was six metres wide, so he put three-metre extensions on both sides). Then he received a letter from the Enforcement Team saying that that he is in breach of the regulations twice, because as an HMO the building does not have PD rights and the side extension was more than half the width of the property.

I contacted the officer and emailed him, showing clearly that he had mistaken the law on both counts. One: HMO does have PD rights (As attached in the memo below), and second, there is a Planning Inspectorate decision clearly stating that EACH side extension can be half of the width of the house, and they are not calculated together!
A few minutes later I got a message from the client that the council will review the case, and he had no further communications from them.

All the above is regarding the PD, and on the ground floor. However, if you want to extend the first floor you will need a full planning application, and it all depends on the borough in which you live. For example, in Brent they allow it, but you have to move the first-floor extension back from the front elevation between 2 metres to 2.5 metres (as seen below).
I hope this clarifies your question; in any case, it’s always good to go through your house in detail with a Planning Consultant, as there are always some gems hidden where you can maximise the potential of the property.




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