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Is Planning Permission Required For A Glass Extension?


When you’ve just agreed to buy a brand new glass extension for your home from Hazlemere you’ll understandably want it built and up and running as quickly as possible. We want that too, but sometimes one thing can get in the way before any construction can commence – planning permission.

Glass-to-Floor Extension

No-one wants to be held up by planning permission requirements, least of all us, but if planning permission needs to be sought for your proposed glass extension it simply has to be obtained first. You run a huge risk by ignoring these obligations as severe penalties can be imposed, such as your planning department ordering you to completely knock down the extension.

There is a possibility that you will neither have to spend any time or money on attempting to acquire planning permission if you have Permitted Development Rights.

Your glass extension must comply with the full set of rules below to be considered a Permitted Development and not require planning permission:

  • No more than half the area of land around the “original house”* would be covered by additions or other buildings.
  • No extension forward of the principal elevation or side elevation fronting a highway.
  • No extension to be higher than the highest part of the roof.
  • Single-storey rear extension must not extend beyond the rear wall of the original house* by more than three metres if an attached house or by four metres if a detached house.
  • In addition, outside Article 2(3) designated land* and Sites of Special Scientific Interest the limit is increased to 6m if an attached house and 8m if a detached house until 30 May 2019.
  • These increased limits (between 3m and 6m and between 4m and 8m respectively) are subject to the prior notification of the proposal to the Local Planning Authority and the implementation of a neighbour consultation scheme. If objections are received, the proposal might not be allowed. If a single neighbour objects you’ve lost 6-8 weeks and will then need to apply for planning permission, so frankly it is far faster to apply for full planning permission in the first place.
  • Current PD Rights permit a conservatory to be built without the need for planning if they do not exceed 3m or 4m metres from the original rear wall of the original property depending on whether your property is terraced/semi-detached or detached.
  • Maximum height of a single-storey rear extension of four metres.
  • Extensions of more than one storey must not extend beyond the rear wall of the original house* by more than three metres.
  • Maximum eaves height of an extension within two metres of the boundary of three metres.
  • Maximum eaves and ridge height of extension no higher than existing house.
  • Side extensions to be single storey with maximum height of four metres and width no more than half that of the original house.
  • Two-storey extensions no closer than seven metres to rear boundary.
  • Roof pitch of extensions higher than one storey to match existing house.
  • Materials to be similar in appearance to the existing house.
  • No verandas, balconies or raised platforms.
  • Upper-floor, side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor.
  • On designated land* no permitted development for rear extensions of more than one storey.
  • On designated land no cladding of the exterior.
  • On designated land no side extensions.

* The term “original house” means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date). Although you may not have built an extension to the house, a previous owner may have done so.

* Designated land includes conservation areas, national parks and the Broads, Areas of Outstanding Natural Beauty, and World Heritage Sites.

Leave planning permission to us

We never leave our customers in the lurch! If there is a need for a planning application to be submitted prior to us starting work, we will handle this on your behalf in an efficient manner.

For now, you just concentrate on choosing which of our fabulous glass extensions you love the most and then ask for a FREE quote.


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Credit is subject to status and affordability. Terms and conditions apply. Finance on windows & doors is available to a maximum loan value of £50,000 with zero deposit. Finance on conservatories is available to a maximum loan value of £30,000 with a 15% deposit. £1,000 minimum order value applies to all finance options. Authorised and regulated by the Financial Conduct Authority. Hazlemere Window Company Limited at Cressex Business Park, Wellington Road, High Wycombe, Buckinghamshire HP12 3PR (Financial Services Registered No. 796507) is a credit broker and is authorised and regulated by the Financial Conduct Authority. Credit provided by Hitachi Personal Finance, a trading style of Hitachi Capital (UK) PLC, authorised and regulated by the Financial Conduct Authority (Registered No. 704348).