Building regs: 30 mins fire resistance

Discussion in 'Misc DIY' started by Ben Schofield, Feb 12, 2004.

  1. Hi all,

    I live in the attic of a house which has been converted into flats.
    During the decoration (ahem) of the lounge, I've opened up a storage
    space under one of the eaves, which was previously closed off. Before
    I board out this space, I think I ought to meet current building regs
    with regard to creating a fire compartment here. As this is a
    three-storey flat conversion, the building regs say that 30 minutes
    `could' be acceptable here.

    The space has a suspended ceiling (belonging to the flat below) about
    1m underneath it.

    So, my question is: will 9.5mm of plasterboard and 18mm of chipboard,
    plus the suspended ceiling below, give me the 30 mins fire resistance
    I require? What about 18mm of chipboard alone? Or is this one for the
    local BCO? :)

    Ben.
    Ben Schofield, Feb 12, 2004
    #1
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  2. Ben Schofield

    Peter Parry Guest

    On 12 Feb 2004 14:38:38 -0800, (Ben
    Schofield) wrote:


    >The space has a suspended ceiling (belonging to the flat below) about
    >1m underneath it.
    >
    >So, my question is: will 9.5mm of plasterboard and 18mm of chipboard,
    >plus the suspended ceiling below, give me the 30 mins fire resistance
    >I require?


    If you are going over someone elses property then no matter what the
    BR say think of your own security. Make sure the compartment is
    smoke proof for a start - fires rarely kill - their combustion
    product beat them to it. It used to be that a double layer of
    plasterboard was adequate to give 30 min resistance - I'm not sure if
    this is still so but it isn't far out.

    The suspended ceiling should be ignored in any fire resistance
    estimations.

    >What about 18mm of chipboard alone?


    No.

    --
    Peter Parry.
    http://www.wpp.ltd.uk/
    Peter Parry, Feb 12, 2004
    #2
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  3. On Thu, 12 Feb 2004 23:03:57 +0000, Peter Parry <>
    wrote:

    > >The space has a suspended ceiling (belonging to the flat below) about
    > >1m underneath it.
    > >
    > >So, my question is: will 9.5mm of plasterboard and 18mm of chipboard,
    > >plus the suspended ceiling below, give me the 30 mins fire resistance
    > >I require?

    >
    > If you are going over someone elses property then no matter what the
    > BR say think of your own security. Make sure the compartment is
    > smoke proof for a start - fires rarely kill - their combustion
    > product beat them to it. It used to be that a double layer of
    > plasterboard was adequate to give 30 min resistance - I'm not sure if
    > this is still so but it isn't far out.


    Thanks Peter, I hadn't thought of that. I'll fill the gaps between the
    joists, that ought to do it smoke-wise...

    Googling, I think that the floors in the rest of the flat have been
    filled with something called `foamed perlite', which apparently has 60
    minutes fire resistance, so I'd better meet that in the new
    compartment too...

    Ben.
    Ben Schofield, Feb 13, 2004
    #3
  4. Ben Schofield

    Peter Taylor Guest

    Peter Parry wrote
    > On 12 Feb 2004 14:38:38 -0800, (Ben
    > Schofield) wrote:
    >
    >
    > >The space has a suspended ceiling (belonging to the flat below) about
    > >1m underneath it.
    > >
    > >So, my question is: will 9.5mm of plasterboard and 18mm of chipboard,
    > >plus the suspended ceiling below, give me the 30 mins fire resistance
    > >I require?

    >
    > If you are going over someone elses property then no matter what the
    > BR say think of your own security. Make sure the compartment is
    > smoke proof for a start - fires rarely kill - their combustion
    > product beat them to it. It used to be that a double layer of
    > plasterboard was adequate to give 30 min resistance - I'm not sure if
    > this is still so but it isn't far out.
    >
    > The suspended ceiling should be ignored in any fire resistance
    > estimations.


    Assuming the original conversion work complied with Building Regulations, I
    would be extremely surprised if the 30 minute FR compartmentation covered only
    the area within the eaves voids. Normally it would extend to the outside walls
    all round. This, coupled with sound insulation, is probably the reason why
    there is a suspended ceiling at all. But, either way, here's a thought - if you
    provide 30 minute FR doors to the void areas there will be no need to upgrade
    the ceiling anyway.

    The British Gypsum website http://www.british-gypsum.com/immediacy-824 gives FR
    figures for various configuations of plasterboards/joists/floorboards etc.

    I don't think it is strictly necessary to apply for Building Regulations
    permission to do this work. Providing access to eaves voids, if only for
    maintenance, is normal procedure and this is usually through the short walls at
    attic level, rather than through the ceiling below. However, it's probably wise
    to ask the Building Control office for their views as there may be special
    circumstances here. They may even have kept archived records of the conversion
    work itself.

    Peter
    Peter Taylor, Feb 13, 2004
    #4
  5. Ben Schofield

    River Tramp Guest

    I would have said that to achieve 30min FR with a ceiling of 9.5mm pb, you
    need t & g boarding, and the floor void needs 60mm mineral wool on chicken
    wire mesh stapled to the joists. For FR purposes only, in the voids you
    could do away with the boarding and use 100mm mineral wool instead (but not
    if sound insulation is required).

    We also would not accept the FR door into the voids; inlike some BC
    authorities, we required the entire floor eaves to eaves to have the full
    fire resistance. Nowadays all authorities would require the voids boarded
    out for sound insulation purposes (eg when doing a loft conversion).

    RT



    "Peter Taylor" <> wrote in message
    news:Ky3Xb.2843$9.net...
    > Peter Parry wrote
    > > On 12 Feb 2004 14:38:38 -0800, (Ben
    > > Schofield) wrote:
    > >
    > >
    > > >The space has a suspended ceiling (belonging to the flat below) about
    > > >1m underneath it.
    > > >
    > > >So, my question is: will 9.5mm of plasterboard and 18mm of chipboard,
    > > >plus the suspended ceiling below, give me the 30 mins fire resistance
    > > >I require?

    > >
    > > If you are going over someone elses property then no matter what the
    > > BR say think of your own security. Make sure the compartment is
    > > smoke proof for a start - fires rarely kill - their combustion
    > > product beat them to it. It used to be that a double layer of
    > > plasterboard was adequate to give 30 min resistance - I'm not sure if
    > > this is still so but it isn't far out.
    > >
    > > The suspended ceiling should be ignored in any fire resistance
    > > estimations.

    >
    > Assuming the original conversion work complied with Building Regulations,

    I
    > would be extremely surprised if the 30 minute FR compartmentation covered

    only
    > the area within the eaves voids. Normally it would extend to the outside

    walls
    > all round. This, coupled with sound insulation, is probably the reason

    why
    > there is a suspended ceiling at all. But, either way, here's a thought -

    if you
    > provide 30 minute FR doors to the void areas there will be no need to

    upgrade
    > the ceiling anyway.
    >
    > The British Gypsum website http://www.british-gypsum.com/immediacy-824

    gives FR
    > figures for various configuations of plasterboards/joists/floorboards etc.
    >
    > I don't think it is strictly necessary to apply for Building Regulations
    > permission to do this work. Providing access to eaves voids, if only for
    > maintenance, is normal procedure and this is usually through the short

    walls at
    > attic level, rather than through the ceiling below. However, it's

    probably wise
    > to ask the Building Control office for their views as there may be special
    > circumstances here. They may even have kept archived records of the

    conversion
    > work itself.
    >
    > Peter
    >
    River Tramp, Feb 13, 2004
    #5
  6. Ben Schofield

    Peter Taylor Guest

    "River Tramp" <> wrote in message
    news:402d40bb$0$6850$...
    > I would have said that to achieve 30min FR with a ceiling of 9.5mm pb, you
    > need t & g boarding, and the floor void needs 60mm mineral wool on chicken
    > wire mesh stapled to the joists.


    According to British Gypsum White Book (Section c60 page 5), min 18mm T&G
    boarding, 47mm thick joists at 450c/c and 9.5mm wallboard with 2mm skim finish
    gives 30 minutes FR. No quilt is needed.
    http://www.british-gypsum.com/PDF/c60_093.pdf

    > For FR purposes only, in the voids you
    > could do away with the boarding and use 100mm mineral wool instead (but not
    > if sound insulation is required).
    >
    > We also would not accept the FR door into the voids; inlike some BC
    > authorities, we required the entire floor eaves to eaves to have the full
    > fire resistance.


    That's what I would expect too. I'd be surprised if any extra fire resistance
    is needed in the voids.

    Peter
    Peter Taylor, Feb 14, 2004
    #6
  7. Ben Schofield

    Nick Brooks Guest

    Peter Parry wrote:
    > On 12 Feb 2004 14:38:38 -0800, (Ben
    > Schofield) wrote:
    >
    >
    >
    >>The space has a suspended ceiling (belonging to the flat below) about
    >>1m underneath it.
    >>
    >>So, my question is: will 9.5mm of plasterboard and 18mm of chipboard,
    >>plus the suspended ceiling below, give me the 30 mins fire resistance
    >>I require?

    >
    >
    > If you are going over someone elses property then no matter what the
    > BR say think of your own security. Make sure the compartment is
    > smoke proof for a start - fires rarely kill - their combustion
    > product beat them to it. It used to be that a double layer of
    > plasterboard was adequate to give 30 min resistance - I'm not sure if
    > this is still so but it isn't far out.
    >
    > The suspended ceiling should be ignored in any fire resistance
    > estimations.
    >
    >
    >>What about 18mm of chipboard alone?

    >
    >
    > No.
    >


    Double layer of 12.5mm plaster board does meet 30 min requirement. So
    does single layer of 12.5mm firecheck plasterboard which is slightly
    pink in colour, but it's very heavy especially in 8x4 sheets.

    Nick
    Nick Brooks, Feb 16, 2004
    #7
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