Question: We are going to have a baby, so we need to extend our detached home to make more room for the new arrival. Our garden is certainly big enough to take an extension to our property and we have discussed our plans with our nearest neighbours who, I am very pleased to say, have given us their full support.

What I need to know is just how large can we build this new extension without all the bother of having to apply for planning permission?

Answer: The number of applications for “Notification for Prior Approval for a Proposed Larger Home Extension” — known as an NPA — submitted in England increased by three per cent in 2017-2018.

Since this classification of “larger” home extensions was introduced in 2015, its popularity among householders has resulted in this permitted development being made permanent.

So you may be able to build a rear extension to a depth of eight metres, up to a height of four metres (three metres at the eaves) without full planning permission.

Your council will need to consult your neighbours before you start building. Therefore, it is always advisable to discuss your aims with your neighbours first, as you’ll discover most people find it difficult to contextualise plans without correct guidance.

If you don’t inform your neighbours, you could run the risk of receiving an objection. Your architect should make sure that the design does not create a loss to neighbouring daylight/ sunlight, an increase in overshadowing or create an unattractive building.

If your council receives an objection, it will usually refer to its Local Plan to assess whether the development complies with design or amenity protection policies.

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In the case of a semi/terrace house, homeowners could build an extension projecting to six metres and a height of four metres (three metres at the eaves and subject to a neighbour consultation).

You will not be able to apply for a larger home extension if you live in a National Park, an Area of Outstanding Natural Beauty, a conservation area or a World Heritage Site.

If your property lies in a protected area or if your NPA is subsequently refused, then you may construct a smaller rear extension which should not project more than four metres in depth or exceed four metres in height (three metres at the eaves).

Check with your council to see if permitted development rights have been removed within your local area, or from your property via an existing planning condition.

There are other factors you should consider that apply to all applications made under Class A of the General Permitted Development Order 2015/2019.

Your extension should not cover more than 50 per cent of the surface area of your property (excluding the area covered by the original house). Maintain a minimum two-metre gap from the side boundaries and at least seven metres from the opposing rear boundary.

All materials used to build the extension should match those used in your property’s original construction and if your property lies within a protected area, the use of stone, artificial stone, pebbledash, render, timber, plastic or tile cladding is prohibited.

Selwyn Atkinson MRTPI is an associate town planner at Ingleton Wood LLP.



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