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What constitutes a flat roof?

  • 08-10-2020 05:01PM
    #1
    The Mighty Quinn
    Registered Users, Registered Users 2 Posts: 1,229 ✭✭✭


    Can't see to find a definition of a flat roof in TGD L.

    I have a roof with a slope of 1:25, or 2.2°. To me, this is a flat roof. I'm trying to see if I need to meet a u-value of 0.20 W/m²K for flat, or 0.16 W/m²K for pitched.

    I'm using a Kingspan panel which the literature says gives me a u-value of 0.14 W/m²K, but I know myself that by the time you factor in purlins and that, it ends up not being as good as you think.

    If anybody can point me definitively to where I might find this?


Comments

  • #2
    Biker1
    Registered Users, Registered Users 2 Posts: 427 ✭✭Biker1


    BS6229 defines a flat roof as having a pitch of less than 10 degrees.


  • #3
    The Mighty Quinn
    Registered Users, Registered Users 2 Posts: 1,229 ✭✭✭The Mighty Quinn


    Biker1 wrote: »
    BS6229 defines a flat roof as having a pitch of less than 10 degrees.

    Is this referenced in the technical guidance documents anywhere though? I did a search throught TGD L and this doesn't appear to be referenced.


  • #4
    sydthebeat
    Subscribers, Paid Member Posts: 44,136 ✭✭✭✭sydthebeat


    The Mighty Quinn wrote: »
    Is this referenced in the technical guidance documents anywhere though? I did a search throught TGD L and this doesn't appear to be referenced.

    TGD F defines flat roofs as a roof with a pitch less than 15 degrees.

    https://www.housing.gov.ie/sites/default/files/publications/files/tgd_f_2019_-_with_corrections_since_publication.pdf

    BS 6229: 2018 defines it as 10 degrees

    there is absolutely no question that a roof of 2.2 degrees is a flat roof.


  • #5
    The Mighty Quinn
    Registered Users, Registered Users 2 Posts: 1,229 ✭✭✭The Mighty Quinn


    Thanks Syd.

    You'd think it might be a fundamental in a document prescribing requirements to offer a definition of what their terms are. I was 99% sure I had a flat roof, even though in reality it's not flat at all, it's a modest pitch. I was just unsure where the cut off would be.


  • #6
    sydthebeat
    Subscribers, Paid Member Posts: 44,136 ✭✭✭✭sydthebeat


    The Mighty Quinn wrote: »
    Thanks Syd.

    You'd think it might be a fundamental in a document prescribing requirements to offer a definition of what their terms are. I was 99% sure I had a flat roof, even though in reality it's not flat at all, it's a modest pitch. I was just unsure where the cut off would be.

    "flat" roofs are not supposed to be technically flat


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  • #7
    The Mighty Quinn
    Registered Users, Registered Users 2 Posts: 1,229 ✭✭✭The Mighty Quinn


    sydthebeat wrote: »
    "flat" roofs are not supposed to be technically flat

    I know, but at some point a pitched, 'flat', roof becomes a pitched, 'pitched' roof in the eyes of the legislation and I wasn't sure where that arbitrary line is drawn.


  • #8
    Gumbo
    Moderators, Society & Culture Moderators Posts: 41,427 Mod ✭✭✭✭Gumbo


    The Mighty Quinn wrote: »
    I know, but at some point a pitched, 'flat', roof becomes a pitched, 'pitched' roof in the eyes of the legislation and I wasn't sure where that arbitrary line is drawn.

    I think the below is pretty definitive
    Roofs with a pitch of 15° or more (Pitched Roofs)

    So I think 15 degrees is that arbitrary line. The BS code might state differently but the TGD is an Irish standard.


  • #9
    The Mighty Quinn
    Registered Users, Registered Users 2 Posts: 1,229 ✭✭✭The Mighty Quinn


    Hi Gumbo, I know that now, that was the information I was looking for, Syd kindly obliged.

    I was merely saying that they discuss requirements for flat roofs in L, but don't mention what is considered a flat roof in L.


  • #10
    Gumbo
    Moderators, Society & Culture Moderators Posts: 41,427 Mod ✭✭✭✭Gumbo


    The Mighty Quinn wrote: »
    Hi Gumbo, I know that now, that was the information I was looking for, Syd kindly obliged.

    I was merely saying that they discuss requirements for flat roofs in L, but don't mention what is considered a flat roof in L.

    Part L stipulates that it should be read in conjunction with part F but I get your point.

    I guess the idea is that if part f recommendations for a flat roof changes in the future, then they don’t have to reprint part L with an amendment to match part f.


  • #11
    Lumen
    Registered Users, Registered Users 2 Posts: 30,510 ✭✭✭✭Lumen


    Why aren't flat roofs called level roofs?

    Like, we don't use a spirit flat, do we?


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  • #12
    sydthebeat
    Subscribers, Paid Member Posts: 44,136 ✭✭✭✭sydthebeat


    Lumen wrote: »
    Why aren't flat roofs called level roofs?

    Like, we don't use a spirit flat, do we?

    Cos flat roofs aren't level???

    :D


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