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In July 2017, following the Grenfell fire,
the Chair of the Independent Review of Building Regulations and Fire Safety,
Judith Hackitt, issued a report reviewing the Building Regulations 2010. The
conclusion: a more robust regulatory system for the construction industry is
called for. The British government responded to the Hackitt report by issuing
the Building (Amendment) Regulations 2018 – banning the use of combustible
materials in the external walls of buildings – and by adapting the Approved
Documents that accompany the Building Regulations 2010. These Documents provide
practical guidance on how building professionals can achieve compliance. Among
them was the Approved Document B (ADB) on fire safety.
The 2019 edition of ADB brought along several
changes affecting roofing. For one, the principal determinant of external fire
performance for roofs is no longer the national classification system BS 476-3:2004, but the European
classification system BS EN 13501-5 (which ran alongside the national classification system for years). The latter
comes with five European class ratings: BROOF(t4), CROOF(t4),
DROOF(t4), EROOF(t4) and FROOF(t4). In what
follows, we explain the details of the fire standards for roofs and how they
correspond to the old classification system. We will also provide an overview
of SOPREMA waterproofing systems that have a BROOF(t4) rating,
indicating the highest performance.
If you want to know more about Requirement B4
and the recent understanding on the term ‘specified attachment’ that has been
reached in line with the new BS8579 ‘Guide to the Design of Balconies and
Terraces’, we’d like to refer you to our article on the updated ban on
combustible materials.
REGULATION
7(2)
Among other requirements, the Building
Regulations 2010 stipulate that
√“The
external walls of the building shall adequately resist the spread of fire over
the walls and from one building to another, having regard to the height, use
and position of the building.”
√“The
roof of the building shall adequately resist the spread of fire over the roof
and from one building to another, having regard to the use and position of the
building.”
To meet those demands, regulation 7(2)
prescribes that “materials which become part of an external wall, or specified
attachment, of a relevant building are constructed of materials rated A2-s1,d0
or A1 in line with Classification BS EN 13501-1”.
BS EN
13501-5 AND ITS 4 ROOF TESTS
BS EN
13501-5 classification refers to four separate roof testing
methods (DD CEN/TS 1187:2012) that measure the performance of roofs. Test 1
with burning brands, test 2 with burning brands and wind, test 3 with burning
brands, wind and supplementary radiant heat.
Test 4 evaluates
the performance of a roof under the conditions of thermal attack with burning
brands, wind and radiant heat. The test gauges external fire spread and
penetration by fire. One specimen is examined in the preliminary test. Three
other specimens are assessed in the penetration
test, with at least one specimen containing samples of the joint details in
each layer of the roof system. The suffix (t4) indicates that Test 4 is to be used, with BROOF(t4)
indicating the highest performance and FROOF(t4) the lowest.
BROOF(T4)
TO FROOF(T4)
Based on test 4, we arrive at the following
classification system for roofs and roof coverings exposed to external fire:
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BS EN
13501-5 classification (newer)
Classification using data from external
fire exposure to roof tests [2016] (European standards)
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BS 476-3
classification (former)
BS 476-3 classification and testing method
for external fire exposure to roofs [2004]
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BROOF(t4)
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AA, AB or AC
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CROOF(t4)
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BA, BB or BC
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DROOF(t4)
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CA, CB or CC
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EROOF (t4)
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AD, BD or CD
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FROOF (t4)
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DA, DB, DC or DD
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√BROOF(t4)
No penetration of roof system within 60
minutes
In preliminary test, after withdrawal of the
test flame, specimens burn for less than 5 minutes
In preliminary test, flame spread less than
0.38 m across region of burning
√CROOF(t4)
No penetration of roof system within 30
minutes
In preliminary test, after withdrawal of the
test flame, specimens burn for less than 5 minutes
In preliminary test, flame spread less than
0.38 m across region of burning
√DROOF(t4)
Roof system is penetrated within 30 minutes
but is not penetrated in the preliminary test
In preliminary test, after withdrawal of the
test flame, specimens burn for less than 5 minutes
In preliminary test, flame spread less than
0.38 m across region of burning
√EROOF (t4)
Roof system is penetrated within 30 minutes
but is not penetrated in the preliminary test
Flame spread is not controlled
√FROOF (t4)
No performance determined
CORRESPONDENCE
TO BS 476-3:2004
For purposes of clarification, the roof
covering classification BS EN 13501-5 is transposed to the former national
classification system in the table below:
LIMITATIONS
ON ROOF COVERINGS
With the classifications ranging from BROOF(t4)
to FROOF (t4) also come certain separation distances or minimum
distances from the roof, or part of the roof, to the so-called ‘relevant
boundary’. Approved Document B defines a relevant boundary as: “the boundary or
notional boundary (a boundary presumed to exist between two buildings on the
same site) that one side of the building faces and/or coincides with, and that
is parallel or at an angle of a maximum of 80 degrees to that side of the
building.”
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BROOF(t4)
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Unrestricted; can be used anywhere on the
roof
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CROOF(t4)
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At least 6 m from the boundary
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DROOF(t4)
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At least 6, 12 or 20 m from the boundary
(depending on the building type and use)
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EROOF (t4)
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At least 6, 12 or 20 m from the boundary
(depending on the building type and use)
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FROOF (t4)
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At least 20 m from the boundary
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JUNCTION OF
COMPARTMENT WALL WITH ROOF
Approved Document B also includes regulations
on compartmentation, which reduces the spread of fire (with fire stopping in
walls and floors) in paragraphs 5.12 to 5.14:
√“To
reduce the risk of fire spreading over the roof from one compartment to
another, a 1500 mm wide zone of the roof, either side of the wall, should have
a covering classified as BROOF(t4), on a substrate or deck of a material rated
class A2-s3, d2 or better.”
√“Materials
achieving class B-s3, d2 or worse used as a substrate to the roof covering and
any timber tiling battens, fully bedded in mortar or other suitable material
for the width of the wall, may extend over the compartment wall in buildings
that are a maximum of 15 m high.”
√“Double-skinned
insulated roof sheeting should incorporate a band of material rated class
A2-s3, d2 or better, a minimum of 300 mm in width, centred over the wall.”
A visualisation will make this more clear:
Approved Document B includes an alternative
to the provisions of paragraphs 5.12 to 5.14, too: in two cases, “the
compartment wall may extend through the roof for a minimum of either of the
following (see Diagram 5.2c)”, namely: “where the height difference between the
two roofs is less than 375 mm, 375 mm above the top surface of the adjoining
roof covering” and “200 mm above the top surface of the adjoining roof covering
where either of the following applies: a) the height difference between the two
roofs is 375 mm or more, or b) the roof coverings either side of the wall are
of a material classified as BROOF(t4).”
Contact Us:
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