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Confused on Extension Roof Pitch and PD and PP

Discussion in 'Building Regulations and Planning Permission' started by GateBeam, 22 Aug 2019.

  1. GateBeam

    GateBeam

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    Hi everyone,

    Roof Pitch2-1.png
    [​IMG]
    https://imgur.com/a/IgWeLEn

    According to this drawing I made, what colour is the best option for my 5000mm Extension?

    3500mm is the max height until I hit my window

    Purple is the current plans, but it is only 10 degrees

    Red meets 18 degrees which I think is the minium for PD

    Blue is 20 degrees which is considered safe

    Green is how long I have to have to room (2400mm) to meet 20 degrees ratio

    Which one of these falls under PD or PP?

    Thank you
     
  2. tony1851

    tony1851

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    For permitted development, you are limited to 4m maximum height - so it's the red line.
    If it rises above the window cill, you do a cut-out lined with lead, though it doesn't look as good inside, unless you have a flat ceiling.
    Alternatively, as 5m is a big distance out to get a reasonable pitched roof on, why not consider a warm flat roof with lantern?
    Or have a gable roof with a central ridge at right-angles to the house wall.
     
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  3. GateBeam

    GateBeam

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    Thanks for your reply, really helpful. :)
    I ideally want to keep the Extension below the Window Cill, because a Cut-Out as you said, does not look as good.
    Also, I'm not too keen on a Warm Flat roof with Lantern either and if possible, keep a pitched roof.
    So knowing this, I think the Purple Line is the best option because It meets my requirements.
    However, would the Purple Line 10 Degrees be allowed under PD?
    Thanks again (y)
     
  4. catlad

    catlad

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    Well I've seen a few extensions with 10° roofs and they look terrible and leak, as for skylights forget it.
    You need a flat roof if you insist on going out 5mts
     
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  5. tony1851

    tony1851

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    @op, Cat is correct.
    If you go down to 10 deg., your choice of tile will be very limited - you might even need metal.
    Consider also that at 5m out, you will need roofights to get daylight into the existing rear room(s), otherwise they will be dark.
    For rooflights, you generally need a minimum pitch of 15 deg for weathertightness, which means your purple line would not comply.
    Save yourself grief and go with a warm flat roof + lantern, finished in grp or EPDM.
     
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  6. GateBeam

    GateBeam

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    @catlad
    I see, it seems tile is not the way to go for 10 Degrees, but what about 10 Degrees with with Felt, EPDM or GRP? I assume that would be better than flat for 5m.
     
  7. GateBeam

    GateBeam

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    @tony1851
    Great points however sorry you can't see from this drawing, but there will be daylight to the existing rear room because of a existing window which means is it not necessary for rooflights I assume.
    But a flat roof with lantern does sound good, however I am wondering if that would be come under PD?
    Because the lantern will possibly rise above the 4m PD limit, so in this case 10 Degrees with a Felt, EPDM or GRP roof would be a better option?
     
  8. ^woody^

    ^woody^

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    Where is Freddie when you need him. :rolleyes:

    Tiled roof below the recommended pitch, with a boarded and felted layer beneath.
     
  9. GateBeam

    GateBeam

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    @^woody^
    Sorry I'm not sure what you mean. Are you saying felt + board + tile?
    Thanks
     
  10. ^woody^

    ^woody^

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    I am. But board + flat roof felt + tile.
     
  11. catlad

    catlad

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    You don't need a roof lantern Velux do flat roof windows that will open with your phone if that turns you on.
    O
     
  12. Bluepeppo

    Bluepeppo

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    At 5m a GRP flat roof with a lantern is most likely the right solution. A parapet wall will stop it looking cheap for not a lot more money.
     
  13. Leofric

    Leofric

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    don't forget the tantalised battens and counter battens - for very low pitch roofs - tiles on battens on counter battens on suitable membrane on sarking boards on rafters :)oops: I've said it again :!:)
    ps that doesn't mean I am saying a tiled low pitch roof is necessarily the best solution in this case.
     
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  14. Nakajo

    Nakajo

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    Ooh, how tantalising
     
  15. ^woody^

    ^woody^

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    Yes this could be tantalising in certain circumstances, but some tiles at low pitches can look crap, so is not always best option.

    Yes and the counter battens need thought given to the roof depth, and fascia design
     
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