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Rear Extension - the 45 degree rule

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henrik1971henrik1971 Forumite
202 posts
We live in a semi-detached bungalow and are thinking of extending to the rear.
Both ourselves and the other house we're joined on to already have single storey extensions. There is a fence and a hedge along the boundary line between the two properties, and our two extensions are stepped in by a couple of feet on each side of that boundary fence.

We want to make our single storey flat roof extension about 15 feet longer, but I've heard about the 45 degree rule that the planners can use to prevent such a thing. My query is - as there has always been a close-boarded fence 1.8m high between the properties and a hedge about 2.5m high does this mean they couldn't object to the extension on the grounds of shadowing next door's property as there has always been a physical barrier there anyway? I would guess the extension would be about 3m high in total - so a couple of feet higher than the existing hedge.

Any advice or answers would be welcome.


  • DoozergirlDoozergirl Forumite
    30.7K posts
    Part of the Furniture 10,000 Posts Name Dropper Photogenic
    The 45 degree rule (which is a guideline) only applies to second storeys.
    Everything that is supposed to be in heaven is already here on earth.
  • Around our way the 45 degree rule applies to single stories too, but can be omitted so long as the 25 degree vertical rule isn't breached.
    Recently I did a design and build extension which sounds similar to yours the planners allowed the flanking wall at the boundary so long as it didn't exceed the height of the existing boundary fence provided the roof was of a certain pitch, sorry can't remember, what that was, but 27 degrees is something I have in my head.
    Simple answer is to arrange a pre-app consultation with the planners.
  • Thanks for the responses.

    I hear that some Councils apply the 45 degree rule to single storey buildings, so I suppose a pre-app enquiry might be the only way to be sure. Round here, because of cuts to funding, the planners won't speak to you unless you either make an application or otherwise pay for advice. Might be worth speaking to a local planning consultant instead....?

    Pitch of the roof shouldn't be an issue as planning to have a flat roof, as existing extension has flat roof, and would want new extra bit to be 'in keeping'. Pitched would be preferable, but I'll get a decent quality covering and planning to put a couple of aluminium framed roof lanterns in both for daylight and aesthetics.
    Also thinking of putting a full height glass wall 12ft wide x8ft high on the end elevation that overlooks the garden. Two further queries for anyone who might be in the know..:
    1. I'm told glazing per sqm is cheaper than brickwork. Is this true, especially for something bespoke like I'm planning?
    2. Would triple glazing be advisable and how much better is it than the best double glazing? I'm imaging it to be 3 panels 4ftx8ft each.
  • edited 17 November 2015 at 8:35AM
    DoozergirlDoozergirl Forumite
    30.7K posts
    Part of the Furniture 10,000 Posts Name Dropper Photogenic
    edited 17 November 2015 at 8:35AM
    Glazing is not cheaper than brickwork! No way. Not even just building regs standard windows.

    Google your council's name and 'supplementary planning guidance'. They should provide a guidance document for new building - they would need to refer to their own policies in their reports when rejecting applications.

    A planning consultant is overkill and a pre-app would definitely be cheaper. Any local architect should know the answer but as I said, there should be printed guidance.
    Everything that is supposed to be in heaven is already here on earth.
  • MisterBaxterMisterBaxter Forumite
    666 posts
    Most planning departments these days cover a lot of these simpler enquiries on their website and reserve planning consultations for more major jobs, but if you want a planning consulation most now charge.

    I have found that a quick phone call will often result in useful advice for relatively simple matters such as this, although they won't guarantee such advice. It is often just as easy for them to give you the simple answer as it is to explain the consultation/advice process and most of them want to try and help.
  • Absolutely a quick five minute chat should tell you if they will apply the 45 degree rule. As has been said a local architect will be able to answer your questions.
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