Best Practice Guide 5 Issue 2

8/15/2019 Best Practice Guide 5 Issue 2

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Page 1

Electricalinstallationsand theirimpact on the

fire performanceof domesticpremises used assingle familyhouses

Best Prac ce Guide 5 (Issue 2)


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In electronic format, this Guide is intended to be made available freeof charge to all interested par es. Further copies may be downloaded

from the websites of some of the contribu ng organisa ons.The version of this Guide on the Electrical Safety First website (www.electricalsafety rst.org.uk) will always be the latest. Feedbackon any of the Best Prac ce Guides is always welcome – email bpg@electricalsafety rst.org.uk

Electrical Safety First is supported by all sectors of the electricalindustry, approvals and research bodies, consumer interestorganisa ons, the electrical distribu on industry, professional ins tutesand ins tu ons, regulatory bodies, trade and industry associa ons andfedera ons, trade unions, and local and central government.

*Electrical Safety First (formerly the Na onal Inspec on Council forElectrical Installa on Contrac ng) is a charitable non-pro t makingorganisa on set up in 1956 to protect users of electricity against the

hazards of unsafe and unsound electrical installa ons.

Published by:

Electrical Safety First Unit 331 Metal Box Factory 30 Great Guildford StreetLondon SE1 0HS

Tel: 0203 463 5100

Email: bpg@electricalsafety rst.org.uk

Website: www.electricalsafety rst.org.uk

Electrical Safety First and other contributors believe that the guidanceand informa on contained in this Best Prac ce Guide is correct, butall par es must rely on their own skill and judgement when makinguse of it. Neither Electrical Safety First nor any contributor assumesany liability to anyone for any loss or damage caused by any error oromission in this Guide, whether such error or omission is the result ofnegligence or any other cause. Where reference is made to legisla on,

it is not to be considered as legal advice. Any and all such liability isdisclaimed.

© Electrical Safety Council. November 2015

Best Practice GuideElectrical Safety First is indebted to the followingorganisa ons for their contribu on and/orsupport to the development of this Guide:

Associa on of Building Engineers www.abe.org.uk

BEAMA www.beama.org.uk

Bri sh Gypsum www.bri sh-gypsum.com

BSI Product Services www.bsigroup.com

CEDIA UK www.cedia.co.uk

Certsure www.certsure.com

Chief Fire O cers’ Associa on

www.cfoa.org.uk

Electrical Contractors’ Associa on www.eca.co.uk

Ins tu on of Engineering and Technology www.theiet.org

Intumescent Fire Seals Associa on www.ifsa.org.uk

Knauf Drywall www.knaufdrywall.co.uk

LABC www.labc.co.uk

NAPIT www.napit.org.uk

NHBC www.nhbc.co.uk

SELECT (Electrical Contractors’ Associa onof Scotland) www.select.org.uk

Tenmat Ltd www.tenmat.com

This is one of a series of Best Prac ce Guides produced by ElectricalSafety First* in associa on with leading industry bodies for the bene tof electrical contractors and installers, and their customers.

Consultants to Electrical Safety First:

Interna onal Fire Consultants Ltd www.in ire.com


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Electrical installations and theirimpact on the fire performanceof domestic premises usedas single family houses

1. Aim

1.1 The aim of this Guide is to promote best prac ceby providing prac cal advice and guidance fordesigners, installers, veri ers and inspectorsof domes c electrical installa ons where, as iso en the case, the electrical work requires, or hasrequired, the penetra on of linings forming ceilingsand walls.

1.2 The guidance, which is intended to apply toelectrical installa ons designed a er July 2008, mayalso be of bene t to speci ers, builders, buildingcontrol bodies and other interested par es.

1.3 By following the guidance, it is considered thatelectrical installa on work will not compromise the

re performance provisions that are mandatorilyrequired to be incorporated into domes c premisesunder the relevant building regula ons.

Photo courtesy of Greater Manchester Fire & Rescue Service


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2. Introduction

2.1 This Guide has been produced by Electrical SafetyFirst in associa on with the bodies indicated onpage 2.

2.2 It addresses the impact that electrical installa onsin domes c premises have on the re performanceof loadbearing and non-loadbearing walls and oors(and some mes ceiling membranes) that have a

re containment func on, or are required to carry aload for a prescribed period.

2.3 Fire safety in buildings generally requires that in theevent of a re su cient me is available for peopleto escape from a building:

• certain walls, oors and ceilings providere resistance for the purposes of

construc ng re compartments and/or protected escape routes, and

• the structure resists collapse.

2.4 The advice given in this Guide is aimed largely atpreserving the structural stability of the premisesas much as the re separa on between areas.For example, in most domes c premises, it is

the loadbearing capacity of the oors that isthreatened by early failure of ceiling linings, notthe re separa ng func on.

2.5 Many modern forms of engineered construc onhave an inherently lower level of re resistancewhen compared to more tradi onal forms ofconstruc on, and are heavily reliant on theplasterboard or similar linings for achieving therequisite level of re separa on.

2.6 Much of the guidance is related to the e ect that

the installa on of electrical equipment will haveon the performance of the protec ve linings thatare used to provide re protec on to lightweight joisted or studded construc ons. In the case of theassociated wiring, the need to prevent re frompassing through holes in all elements, whether solidor lightweight, is also addressed.

2.7 Amongst these forms of construc on are narrowsec on solid, stress graded mber joists, plywood/Orientated Strand Board (OSB) webbed ‘I’ joists(‘ mber I beams’), tooth or nail-plated trusses and joists, composite mber studs and lightweight metalstuds. Illustra ons of these vulnerable forms ofconstruc on are to be found in Annex A.

2.8 The re resistance of these elements can easilybe compromised by inadequate re sealingand ‘making good’ a er any penetra on toaccommodate electrical equipment and associatedwiring.

2.9 Electrical equipment that has been iden ed ashaving a direct and signi cant in uence on the reperformance of buildings includes:

• ush-mounted consumer units

• concealed and recessed luminaires,including downlighters

• ush-mounted electrical socket-outlets,ex outlet plates and data points

•ush-mounted switches, detec on

and control devices

• recessed wall luminaires

• concealed speakers.

2.10 The above items all require the removal of a partof the ceiling or wall lining, and replacementwith glass, thin metal or plas c that does notprovide the same level of re protec on to thestructural members, causing a reduc on in the reperformance of the element. These are known as

par al penetra ons .

2.11 In addi on to the in uence that these par alpenetra ons have on the re performance, someinstalla ons can penetrate both linings, such as:

• associated wiring and conduits

• ven la on fans and related ductwork.

2.12 These installa ons have a poten al to compromisethe re containment capability, and guidance isincluded for these situa ons. These are known asfull penetra ons .


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2.13 In addi on to the above items that all have a directin uence on the re performance of oors orwalls, the following items can also have an indirectin uence if the lining provides some or all of theirsupport:

• heavy ceiling-hung luminaires, ligh ngtracks and overhead projectors

• wall-mounted brackets for televisions, heavyspeakers and at screen installa ons.

If the room is involved in re, the weight of suchitems may lead to the premature failure of the lining

material.

2.14 In addi on to the risk of the electrical installa onreducing the re separa on capabili es of thoseelements that need to resist re spread or toremain structurally sound in a re, a poorlyconstructed installa on can poten ally be the cause

of a re, for example due to heat generated byloose connec ons.

2.15 When involved in a re, thermoplas c materialsused in the construc on of electrical ngs canrelease signi cant quan es of dense smoke andtoxic products. They can also create aming moltendroplets which have been known to cause respread to carpets and furnishing below them.

2.16 The re separa ng capability of an element ofconstruc on is generally measured by the dura onfor which the element will sa sfy the criteria of a

re resistance test. Historically, these criteria havebeen determined by exposure to the BS 476: Part20: 1987 hea ng and pressure condi ons, but morerecently by the new European tes ng regime asembodied in BS EN 1363-1. More informa on onthe relevant test methods and criteria can be foundin Annex B.

Result of an eight minute re on lightweight joists (Courtesy of Manchester City Council - Building Control)


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3. Scope

3.1 This Guide gives prac cal advice and guidance forthe installa on, and the making good followingthe installa on, of electrical equipment and wiringin self-contained domes c premises (includingbungalows, mul -storey houses, individual ats andmaisone es) that are designed to accommodate asingle family unit. The advice and guidance appliesto both new and exis ng premises.

3.2 The Guide does not apply directly to Houses inMul ple Occupa on, hostels, caravans or boats,or to the communal parts of blocks of ats or thecommunal parts of maisone es, nor does it apply

to any premises used for purposes other than adwelling (such as small shops, factories or similarpremises used solely as places of work).

3.3 The Guide gives advice on what needs to be doneto maintain the re resistance of walls and ceilingsin domes c premises that have been penetratedor par ally penetrated in the process of installingelectrical equipment and wiring.

3.4 It does not consider in detail the impact that theinstalla on of electrical equipment and wiring mayalso have on the structural, acous c or energytargets prescribed in building regula ons.

3.5 The Guide gives recommenda ons as to what isconsidered to be best prac ce, taking into accountthat electrical installers may not have adequateknowledge of the construc on of the elements thatare poten ally being compromised by their work.

3.6 Where an installer wishes to di eren ate betweennew and tradi onal forms of construc on, theguidance given in Annex C may assist. Someinves ga ons may require the services of anotherprofessional, such as a surveyor or re specialist.

Note: This Guide does not necessarilyapply to all innova ve or unusual forms ofconstruc on or electrical equipment. If indoubt, specialist advice should be sought.


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4. General electrical installation requirements

4.1 This Guide takes into account the publica onof BS 7671: 2008 (Requirements for ElectricalInstalla ons, IET Wiring Regula ons 17th Edi on),which is the latest version of the na onal standardfor the safety of electrical installa ons, rstpublished in 1882.

4.2 BS 7671 requires, in Sec on 421 (Protec onagainst re caused by electrical equipment),that equipment must not present a re hazardto adjacent materials, and that manufacturers’instruc ons must be taken into account. Sec on421 also requires that xed equipment causing

a concentra on and focusing of heat (such asspot lamps) shall be at a su cient distance fromany xed object or building element so that theobject or element is not subjected to a dangeroustemperature in normal condi ons.

4.3 In Sec on 527 (Selec on and erec on of wiringsystems to minimise the spread of re) of thatstandard, it is required that wiring systems areselected and erected to minimise the spread of re,including:

•Within a re-segregated compartment, therisk of the spread of re must be minimisedby the selec on of appropriate materials,and by the appropriate construc on of theinstalla on (Regula on 527.1.1), and

• A wiring system must be installed so thatthe general building structural performanceand re safety performance are notreduced (Regula on 527.1.2), and

• Where a wiring system passes through elementsof building construc on such as oors, walls,roofs, ceilings, par ons or cavity barriers, theopenings remaining a er the passage of thewiring system must be sealed according to thedegree of re resistance (if any) prescribed forthe respec ve element of building construc onbefore penetra on (Regula on 527.2.1).

4.4 Regula on 510.3 requires manufacturers’instruc ons to be taken into account. It isimportant to do this in order, for example, toprevent luminaires becoming a source of igni on.Any installa on instruc ons that are consideredto be inappropriate should be queried with themanufacturer concerned, and amended installa oninstruc ons requested.

4.5 All termina ons and joints, whether for low voltage(LV) or extra-low voltage (ELV) circuits, should beenclosed in accordance with Regula on 526.5 toprevent re spread should a loose connec on occur.

4.6 As part of the ini al veri ca on process, theelectrical installer has a duty to ensure that allthe necessary re precau ons have been taken,irrespec ve of which party was responsible forthat element of the electrical work(Regula on611.3(vii)).


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5. Legal

5.1 Building regula ons for each part of the UKde ne re performance objec ves for the variouselements that make up domes c premises, andgive recommended performance levels in guidancesuppor ng those regula ons. The objec vesare taken into account in this Guide. For furtherinforma on, see Annex D.

5.2 It is vital that the re performance of cri calwalls and oors is maintained to at least the levelrecommended in the guidance suppor ng theregula ons, a er the installa on of electricalequipment and associated wiring.

5.3 For proper es in England and Wales, a en onis drawn to the Party Wall Act. Under this Act,any work undertaken on the party wall betweenproper es which could a ect its performance(or indirectly a ect the structure of an a achedneighbouring property) is a no able ac vity. InScotland, a building warrant is required for anywork that adversely a ects a separa ng wall or asepara ng oor.

5.4 The ng of electrical equipment in a masonryparty wall has never been considered as beingno able, but cu ng holes in the linings andinstalling ‘plas c’ accessories may be deemed to becovered by statutory requirements. Electrical SafetyFirst therefore recommends that the neighbour beadvised of the intended work in order to give themthe opportunity to object to, comment upon, orprevent the work taking place.

5.5 Electrical installa on work will o en be undertakenon behalf of owners or tenants a er the occupa onof the premises and, as such, it is not subject to

any form of third party audit or nal approval. Theelectrical installer is therefore subject to a duty ofcare to ensure that the re performance of thepremises is not compromised. In Scotland, certainworks require building warrant approval dependingon the work proposed and the building type.

Note: In England & Wales, Part P of the Building

Regula ons and, in Scotland, Building Standard4.5, make this a requirement, pu ng theresponsibility on the installer if self-cer fying thework as compliant with building regula ons.

Currently, electrical safety in Northern Irelandis not controlled under building regula ons.


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RECOMMENDATIONS

6. Flush-mounted consumer units

6.1 Flush-mounted consumer units should not beinstalled in a re separa ng wall. In excep onalcircumstances, where this cannot be avoided, andsubject to the agreement of the Local Authority,the enclosure of the consumer unit or a separatebuilder’s work enclosure around the consumerunit must provide a proven level of re resistancecommensurate with the re separa ng element.

Photos courtesy of Hager

Photo courtesy of MK


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7. Downlighters (recessed luminaires)

7.1 When exposed to a re from below, downlightersmay provide far less protec on to a cavity and thestructural elements within it than the plasterboardthey are replacing, unless suitable precau ons aretaken.

7.2 Electrical Safety First recommends that, whereverpossible, downlighters having integral reprotec on are selected for use in all ceilings wherethe lining that is to be penetrated is the sole meansof keeping re and heat out of the cavity.

7.3 There are a number of types of downlighteravailable, and it is important that the type selectedfor a par cular applica on has test evidence tosupport its re performance when incorporated in aceiling of the type into which it is to be installed.

7.4 Generally, the tests should have been carried outin accordance with BS 476: Part 21: 1987 or BS EN1365-2. The nature of the test evidence can becri cal, and is discussed in detail in Annex B.

7.5 Not all designs and styles of downlighter may beavailable with integral re protec on, especiallywhere higher ligh ng levels and/or larger coverageis required. In these situa ons, addi onal reprotec on may be ed at the me of installa on inthe form of a ‘ re hood’, an insulated re-protec vebox, or similar.

7.6 Such separate forms of protec on must bet for purpose and not be easily dislodged or

compromised a er installa on by subsequent work.Any such protec on must conform to the guidancegiven in Annex E.

7.7 Electrical Safety First recommends thatdownlighters installed in a ceiling beneath a roofspace have integral re protec on, or are providedwith some other suitable form of re protec on,in order to safeguard escape from the premises,restrict the spread of re, and reduce the risk ofpremature failure of the roof structure.

7.8 In order to avoid the risk of re (as well as reducedlamp and service life) caused by overhea ng,downlighters and any associated transformers mustnot be covered by thermal insula on. BuildingRegula ons do not prohibit the leaving of a smallarea around downlighters free from thermalinsula on where this is necessary to permit thedissipa on of the heat they generate. However, dueallowance for this should be made in the overallthermal performance of the premises.

A number of studies have shown that the use of“unprotected” downlighters which penetrate intoa lo space account causes signi cant energy loss.The use of approved downlight lo covers allowsthe insula on to be con nuous and uninteruptedthus mee ng current Building Regula ons fully. Anysuch downlighter lo covers should be dust ght toIP6X and meet the requirements of BS EN 60598-1and BS EN 60598-2.2.

7.9 In all cases, manufacturers’ installa on instruc onsshould be taken into account to avoid downlighters

becoming a source of re.

7.10 Guidance on the selec on of suitable types ofdownlighter for par cular applica ons is given inTable 1 of this Guide.

Typical re hood for a downlighter

Typical downlighters with integral re protec on

(Photos courtesy of Safe and Sound Ligh ng Ltd)

Result of a downlighter re(Courtesy of Manchester City Council - Building Control)


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B u i l

d i n g

L o c a o n

C o n s t r u c o n

F i r e R e s i s t a n c e R e q u i r e d

R e c o m m e n

d e d

B u n g a

l o w

R o o

f c e i l i n g

A l l

N / A

A

R o o

f c e i l i n g

A l l

N / A

A

( a s s u m i n g a d e q u a t e c o m p a r t m e n t a o n

b e t w e e n

a d j a c e n t

d w e l

l i n g s

)

R o

b u s t

M o

d i e d 3 0 m i n s *

*

B , C , b

u t A c a n

b e j u s

e d i f t r a d i o n a l c o n s t r u c o n

c o n

r m e d

( A n n e x C

)

L i g h t w e i g h t

M o

d i e d 3 0 m i n s *

*

B , C

B e l o w r o o m

o v e r g a r a g e

A l l

3 0 m i n s

B , C

O v e r

b a s e m e n t

A l l

3 0 m i n s

B , C

R o o

f c e i l i n g

A l l

N / A

A

( a s s u m i n g a d e q u a t e c o m p a r t m e n t a o n

b e t w e e n

a d j a c e n t

d w e l

l i n g s

)

F i r s t a n

d S e c o n

d F l o o r

A l l

3 0 m i n s

B , C

C e i

l i n g o

f g a r a g e u n d e r r o o m

A l l

3 0 m i n s

O v e r

b a s e m e n t

A l l

3 0 m i n s

B , C

R o

b u s t

M o

d i e d 3 0 m i n s *

*

L i g h t w e i g h t

M o

d i e d 3 0 m i n s *

*

B , C , b

u t A c a n

b e j u s

e d i f t r a d i o n a l c o n s t r u c o n

c o n

r m e d

( A n n e x C

)

R o o

f c e i l i n g

A l l

N / A

( A s s u m i n g a d e q u a t e c o m p a r t m e n t a o n

b e t w e e n

a d j a c e n t

d w e l

l i n g s

)

A l l F l o o r s

, i n c l u

d i n g g a r a g e a n

d

b a s e m e n t c e i l i n g s

/ o o r s

A l l

6 0 m i n s

B , C

F l a t s

T o p

o o r < 5 m

C o m p a r t m e n t

o o r

A l l

3 0 m i n

D , B , C

D , B , C

D , B , C

D , B , C

T o p

o o r < 1 8 m


o o r

A l l

6 0 m i n

T o p

o o r < 3 0 m


o o r

A l l

9 0 m i n

T o p

o o r > 3 0 m


o o r

A l l

1 2 0 m i n

D u p l e x

a t s

I n t e r m e d i a t e

o o r

A l l

3 0 m i n

B , C

K E Y :

D =

D o w n l i g

h t e r i n s e r t e d i n

f a l s e

( s e c o n d a r y ) c e i l i n g

B =

D o w n l i g

h t e r w i t

h i n t e g r a l p r o t e c o n

L o c o n v e r s i o n

( 2 - s

t o r e y s t o 3 )

F i r s t

o o r

( w h e n

l o c o n v e r t e d

)

T w o - s t o r e y

h o u s e

T h r e e - s t o r e y

h o u s e

F o u r - s t o r e y

( o r m o r e

)

h o u s e

F i r s t F l o o r

T a

b l e 1 : R e c o m m e n

d a o n s

f o r r e c e s s e

d l u m i n a i r e s

/ d o w n

l i g h t e r s i n

o o r s a n

d c e i l i n g s

* *

= S e e A n n e x F

=

R o

b u s t c o n s t r u c o n i s

d e n e

d i n A n n e x C

=

E n s u r e t h a t t h e r m a l i n s u

l a o n w i l l n o t p r e j u

d i c e

l u m i n a i r e

=

S h o u

l d o n

l y b e i n s t a l

l e d i f i t c a n

b e v e r i

f e d t h a t t h e p e n e t r a o n

w i l l n o t

h a v e a n a d v e r s e i m p a c t o n a c c o u s c p e r f o r m a n c e

=

L i g h t w e i g h t e n g i n e e r e d c o n s t r u c o n i s

d e n e d i n A n n e x A

A =

U n p r o t e c t e d

d o w n

l i g h t e r p e r m i e d

, b u t

s u i t a

b l e r e p r o t e c o n r e c o m m e n

d e d

f o r s a f e t y r e a s o n s

C =

D o w n

l i g h t e r w i t

h h o o

d c o m p

l y i n g w i t

h A n n e x

E

B , C

A B , C


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8. Flush-mounted accessories(including switches, sockets, flex outlet plates, data and telephone points etc.)

8.1 Numerous ush-mounted accessories are commonin modern homes. These generally comprise twocomponents:

• a recessed housing, or back box

• a face plate with integral socket,switch mechanism, ex outlet etc,and associated wiring terminals.

8.2 Back boxes may be either moulded plas c or steelconstruc on, but all designs incorporate large

knockout sec ons, many mes greater in diameterthan the cables passing through them, which makethem very permeable in a re a er the face platehas been destroyed by the heat. This permeabilitywill allow hot gases into the cavity of the wallmuch more rapidly than the plasterboard. For resepara ng applica ons, and for applica ons reliedupon to resist collapse, this should be guardedagainst by providing addi onal localised reprotec on.

8.3 The risks associated with re penetra ng throughush-mounted accessories are signi cant when they

penetrate a 30 minute re-resis ng loadbearingstud wall, ‘back-to-back’ with other accessories inthe same cavity (or interlinked cavi es).

8.4 Therefore, where ush-mounted accessories

penetrate each face of a 30 minute re separa ngor loadbearing plasterboard lined wall within thesame cavity space (that is, the gap between twostuds), each accessory should be ed with a backbox that incorporates integral re protec on, or be

ed with a proprietary re protec on pad, unlessevidence of the re resistance performance of theaccessories is available.

The e ect of re on a socket-outlet (Photo courtesy of Greater ManchesterFire & Rescue Service)

Photo courtesy of Greater Manchester

Fire & Rescue Service

Example of accessories being back-to back in thesame cavity space (can be at di erent heights)

Example of accessories not being back-to-back in thesame cavity

Plan view

Plan view


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Page 13

8.5 Such back boxes or protec ve pads must haveevidence of performance to demonstrate that theyhave the ability to maintain the re separa oncapability of a wall for 30 minutes, were they tobe tested to BS 476: Part 21: 1987 (loadbearing)or BS 476: Part 22 (non-loadbearing), or the ENequivalent as appropriate (see Annex B), with plas caccessories ed in both linings.

8.6 Recommenda ons for the protec on of ush-mounted accessories in mber or metal stud wallsin par cular situa ons are given in Table 2 of thisGuide.

Fire protec on pad ed externally

The box depth must be selected so that with thepad in place, the required clearance is maintainedbetween the pad and the accessory, and the wiringis not unduly distorted.

Fire and acous c rated cover ed behind adry lining box (Photo courtesy of Tenmat Ltd)

Intumescent pad being installed in a dry lining box (Photo courtesy of Knauf Drywall)

Intumescent pad being installed in a dry lining box (Photo courtesy of Knauf Drywall)

Plan view

Plan view


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Page 14

B u i l

d i n g

L o c a o n

F i r e R e s i s t a n c e R e q u i r e

d

R e c o m m e n

d e

d

A l l D w e

l l i n g T y p e s

I n t e r n a l w a l l s w i t h i n a d w

e l l i n g t h a t d o n o t

h a v e a

r e s e p a r a n g

f u n c o n

O n e

l i n i n g o n

l y o r

b a c k - t

o - b a c k

N / A

A

B u n g a l o w

I n t e r n a l w a l l s

N / A

A

S t a i r w a y e n c l o s u r e

N / A

A

O n e l i n i n g o n l y

3 0 m i n

A

B a c k - t o -

b a c k

3 0 m i n

B


N / A

A


3 0 m i n

A

B a c k - t

o - b a c k

3 0 m i n

B


3 0 m i n

A

B a c k - t o -

b a c k

3 0 m i n

B


3 0 m i n

A

B a c k t o

b a c k

3 0 m i n

B

O n e

l i n i n g o n

l y

3 0 m i n

A

B a c k - t

o - b a c k

3 0 m i n

B

O n e

l i n i n g o n

l y

3 0 m i n

A

B a c k - t o -

b a c k

3 0 m i n

B

S e p a r a n g w a l

l b e t w e e n

d w e l

l i n g s #

6 0 m i n

B


6 0 m i n

B

O n e

l i n i n g o n

l y

3 0 m i n

A

B a c k - t

o - b a c k

3 0 m i n

B


6 0 m i n

B


3 0 m i n

A

B a c k - t

o - b a c k

3 0 m i n

B


l b e t w e e n

d w e l

l i n g s #

6 0 m i n

B

F l a t s

T o p

o o r < 5 m

W a l

l s b e t w e e n o c c u p a n c i e s #

F i n g i n o n e o r

b o t h l i n i n g s

3 0 m i n

B

T o p o o r < 1 8 m

W a l




6 0 m i n

T o p o o r < 3 0 m

W a l




9 0 m i n

T o p

o o r > 3 0 m

W a l




1 2 0 m i n

3 0 m i n

A

B a c k - t

o - b a c k

3 0 m i n

B

=

E n s u r e t h a t p r o t e c o n s y s t e m w i l l n o t p r e j u d i c e w i r i n g t o a c c e s s o r y

=

S h o u

l d o n

l y b e i n s t a l

l e d i f i t c a n

b e v e r i

f e d t h a t t h e p e n e t r a o n

A =

U n p r o t e c t e d a c c e s s o r y

w i l l n o t

h a v e a n a d v e r s e i m p a c t o n a c c o u s c p e r f o r m a n c e

B =

A c c e s s o r y i n s t a l

l e d w i t h a p p l i e

d o r i n t e g r a l p r o t e c o n

#

=

F l u s h - m o u n t e d a c c e s s o r i e s s h o u l d n o t b e e d i n t h e s e w a l l s

u n l e s s u n a v o i d a b l e ( N o t p e r m i e d i n S c o t l a n d )

O n e l i n i n g o n l y o r b a c k - t

o - b a c k

O n e l i n i n g o n l y o r b a c k - t o - b a c k

W a l l s e p a r a n g g a r a g e f r o m o t h e r r o o m s

T w o - s t o r e y

h o u s e

( d e t a c h e d

)

I n s t a l

l a o n


o - b a c k



b o t h l i n i n g s #

K E Y :

F o u r - s t

o r e y

( o r m o r e )

h o u s e

W a l

l s e p a r a n g g a r a g e f r o m o t

h e r r o o m s


F o u r - s t

o r e y p l u s

h o u s e ( a a c h e d )

D u p

l e x a t s

T h r e e - s t o r e y

h o u s e

( a a c h e d

)

6 0 m i n


b o t h

l i n i n g s #


T a b l e 2 : R e c o m m e n

d a o n s

f o r

u s h - m

o u n t e

d a c c e s s o r i e s i n m

b e r a n

d m e t a

l s t u

d w a

l l s


l b e t w e e n

d w e l

l i n g s #

T h r e e - s t o r e y h o u s e


T w o - s t o r e y h o u s e

( a a c h e d )



b o t h l i n i n g s #


o - b a c k

O n e

l i n i n g o n

l y o r

b a c k - t

o - b a c k

O n e

l i n i n g o n

l y

B

W a l

l s e p a r a n g g a r a g e f r o m o t

h e r r o o m s

I n t e r n a l s t a i r w a y e n c l o s u r e

B B B


15/28

Page 15

9. Flush-mounted wall luminaires andconcealed speakers in walls or ceilings

9.1 This type of equipment varies signi cantly in size,design and construc on. It is therefore not possibleto give speci c advice in this Guide in respect of thebest method of maintaining the re performance ofthe lining(s) penetrated by such equipment.

9.2 In principle, however, speakers concealed in ceilinglinings should be treated in a similar manner todownlighters, and both luminaires and speakers

ush-mounted in walls should conform to theguidance given for ush-mounted accessories.

9.3 Where a luminaire or speaker has integral reprotec on, then this must be to the appropriatetest standard (see Annex B).

9.4 If the equipment does not have integral reprotec on then, when it is being installed in aceiling or wall that is required to provide resepara on, the equipment has to be provided

with an ad hoc form of re protec on and, whereappropriate, acous c insula on. It may be di cultfor the installer to establish what form of protec onis likely to maintain the required re resistance,and therefore any proposed method of providingprotec on should be tested, or more reasonablyassessed in lieu of test evidence, by thoseauthori es recognised in guidance in support ofregula ons.

9.5 Proprietary protec on is likely to become availablein due course, and should be used when it does.

Photo courtesy of CEDIA/Smartcomm


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Page 16

10. Cables, conduit and trunking penetratinginternal fire separating walls and floors

10.1 This sec on provides guidance as to what shouldbe done to preserve the re resistance of elementsthat are required to provide re resistance, whencables have to pass through them. The guidanceis applicable to situa ons where insulated andsheathed cables, or cables in plas c conduit orplas c trunking, pass through oors and walls.

10.2 The re risk associated with non- re performancecables and plas c conduits and trunking passingthrough building elements is twofold. Ini ally thereis a risk of a loss of integrity due to the heat and/or ames passing through any unsealed holes thathave been made to allow the cable to pass through,resul ng in aming on the unexposed side.

Secondly, the hole in a plasterboard lining will allowre to get into the ceiling or wall void prematurely,

cause igni on of the structure which can lead to aloss of loadbearing capacity.

10.3 With respect to the rst of these, it is importantthat re is not allowed to exploit either the ini alpenetra on of the rst lining (which could permit

re to get into the cavity), or subsequently topenetrate the second lining (which would allow the

re to e ec vely bypass the protec ve barrier).

10.4 Sealing the cable ingress point has to take intoaccount that the insula on of non- re performancecables will probably melt or char away, leaving anun lled gap between the conductors and the lining.Depending upon the nature of the cable insula on,this may even have the poten al to carry the ameson its surface into the void. On a single cable this isunlikely to be a serious risk, but the ability to makean adequate re seal becomes increasingly di cultas the number of cables increase.

10.5 It is common and accepted prac ce to make goodany hole around a cable by using inert ller suchas plaster or grout, but this does not compensatefor mel ng/ aming insula on, and will also beine ec ve in voids between cables.

10.6 It is recommended, therefore, that the sealant usedto make good holes through which cables pass hasintumescent proper es: that is, it has the ability toexpand and ll any voids that are developing dueto movement and/or mel ng of cables, in order tomaintain the re resistance of the element.

10.7 The risk of re gaining premature access to any voidis increased if the cables are run through a plas cconduit or trunking system, or are bunched. Anycosme c sealing of the gap between the lining andthe plas c conduit or trunking will certainly not beable to seal any voids between the cables and theouter plas c casing following the mel ng of theconduit or trunking.

10.8 In elements that require high levels of reresistance, especially where there is a sleepingrisk – that is, a place where people sleep (suchas 60 minute compartment walls and oors), it isrecommended that a proprietary cable transit or a

re resis ng conduit be installed in the construc onelement being penetrated, if services have to passthrough one or both linings that form the wall.

Note: In Scotland, the guidance clause 2.2.6(Domes c Handbook) recommends that combus blesepara ng walls do not contain pipes, wires or otherservices. In buildings with a storey height over 18 m,Clause 2.2.7 states that separa ng walls and oors

must be constructed of non-combus ble materials.

Fire seals around cables and trunking


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Page 17

11. Ventilation fans and related ductwork

11.1 In older proper es, ven la on fans were normallyed on an external wall rather than on an internal

wall and, as a consequence, there was not generallya re safety issue regarding the in uence on theintegrity and insula on ra ng of the wall due tosuch systems when installed in a cavity blockwork ormasonry wall.

11.2 However with ever increasing air ghtnessrequirements, controlled ven la on and, o enheat recovery is the standard for new builds, thismeans combus ble PVC duc ng runs are installedall around the building, o en with both return and

supplies in each room, which can result in rapidspread of re and smoke, both horizontally andver cally through the premises. Where such duc ngpenetrates a re-rated ceiling, intumescent fan andvent sleeves or re-rated air valves should be ed.

Photo courtesy of Tenmat Ltd

11.3 If re were to enter the cavity of a stud wallor the cavity between the inner wall and anyouter ‘sheathing’, the building can su er bothundue structural damage if modern engineeredconstruc on is used, and/or dispropor onate

re spread in the cavity in more conven onalproper es. This cavity spread can result in anindirect loss of re integrity between adjacentinternal enclosures, and therefore re should beprevented from gaining access to any of the cavi es.

11.4 When installing a ven la on fan directly into aloadbearing external stud construc on wall, the

hole cut into the inner and outer lining should belined out across the thickness of the wall with acon nuous non-combus ble material, preferablywith some insula ng proper es, through which theextract duct passes. This liner should be xed inplace so that it does not fall away over me.

11.5 When the vent from for example, a shower cubicle,is connected to an extended duct which runswithin the oor void to an outside wall possiblyvia an in-line fan, then this length of low mel ngpoint ductwork (plas c or aluminium) will have no

measurable re resistance and re entering intothis duct, via the vent, will soon have access to the joists. Indeed, should the fan be in extract mode atthe me of the re, re will be drawn into this voidquite quickly.

Fire spread into bathroom via plas c duct (Photo courtesy of Greater Manchester

Fire & Rescue Service)


18/28

Page 18

11.6 Any void between two joists that contain sucha duct which is running parallel with the joistsshould be lined on the face of both joists with reprotec on board that duplicates the re protec onprovided by the ceiling lining. The void beyond theduct should be separated by a transverse barrier ofthe same ra ng. Similarly, the ooring above mayneed to be underdrawn with re protec on board ifit is bu -jointed.

The method of re sealing the wall/duct interfacewill vary depending upon whether it is a studdedconstruc on or a conven onal masonry cavity wall(see Figures 11a and 11b).

11.7 Where the duct runs transverse to the joists,the amount of joist to be cut away is likely to bestructurally signi cant and expert guidance shouldbe sought, in respect of both the e ect on thestructure and the re separa on measures.

Figure 11a: Joist/wall protec on when installing vent into conven onal masonry wall construc on

Figure 11b: Joist/wall protec on when installing vent into a mber frame wall construc on


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Page 19

12. Wall or ceiling-mounted electrical equipment

12.1 It has become increasingly common to mountheavy equipment such as TVs, speakers, at screeninstalla ons etc on wall brackets, and to hang heavyluminaires, ligh ng track and projectors etc fromthe ceiling.

12.2 Plasterboard linings are not designed to carry suchweights under re condi ons and, unless theseitems are xed back only to the structural membersin the wall or oor, they will pull down the liningsonce the board is weakened by the re.

12.3 Weakening of normal and ‘sound’ gradeplasterboard will occur rapidly a er re hasconsumed the room face paper lining and, whilst

breglass-reinforced board will not fail quite asquickly or as drama cally, xings will pull through itat a fairly early stage in the re a ack.

12.4 Obviously, early failure of these protec ve liningswill allow re a ack on the studs and joists whichagain, if of engineered construc on (see Annex A)will lead to premature structural failure.

12.5 All heavy equipment mounted on the face ofwalls or hung from the ceiling must be supportedcompletely independently from the re protec veplasterboard linings. Whilst it may be permi edto x directly to the joists, false ceiling membersor studs, none of the xings should rely solely onplasterboard.

12.6 If any addi onal xings are needed beyond thosethat the structure is able to provide, then a sec onof the lining should be completely removed and theedges of the ‘hole’ ed with supports to which‘both’ edges of the plaster board can be xed.

12.7 Addi onal structural members should then beed between joists and studs at the required

xing loca ons and the new plasterboard should bescribed, cut to size/shape and xed in accordancewith plasterboard manufacturers’ instruc ons,before ng the suspended equipment. Jointsbetween exis ng and new plasterboard liningsshould be lled and skimmed with plaster.

Photo courtesy of CEDIA/Smartcomm


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Page 20

ANNEX A

Examples of forms of modern engineered

construc on covered by this Guide.

Timber ‘I’ beams; consis ng of Orientated StrandBoard (OSB) or plywood webs with solid mberor laminated mber top and bo om chords.

Space joists; consis ng of mber top andbo om chords spaced apart by pressedsteel ‘boomerangs’ Narrow stress gradedso wood joints (less than 38mm)

Steel webbed, mber ‘I’ beams;consis ng of corrugated steel webs with

mber top and bo om chords

Glue laminated ‘ mber’ studs

Steel ‘C’ studs

Narrow stress graded so wood studs (less than 38 mm)

Punched metal plate connected ‘truss’ joists

Floor Joists

Studs


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Page 21

ANNEX B

Under regulatory guidance there are a number

of re tests called up against which the elements,together with installed components as they will bein prac ce, have to be veri ed. The ability of theelement to sa sfy the structural re requirementsand re separa ng objec ves is adjudged by aseries of established Bri sh and European testprocedures.

The relevant standards are:

• Non-loadbearing walls and ceiling membranes:BS 476: Part 22: 1987, or

BS EN 1364: Parts 1 and 2.

• Loadbearing elements:BS 476: Part 21: 1987, orBS EN 1365: Parts 1 and 2.

• Wires, cables and conduit penetra ng elements: BS EN 1366-3.

• Suspended ceilings that are provided only for theprotec on of steel beams*:BS 476: Part 23: 1987.

Note: there is no directly comparableBS EN test for this purpose.

In respect of these tests, the criteria of failure are

loadbearing capacity (BS 476 Part 21 andBS EN 1365 only), integrity and insula on, which arede ned as follows:

Loadbearing capacity is the ability to carry thedesign loads for the speci ed period withoutcollapse or exceeding pre-determined de ec onlimits.

Integrity is the ability to resist the passage ofames, or the passage of cri cally hot gases

(measured by means of an oven dry co on pad).

Insula on is the ability to restrict temperature riseon the unexposed face to a mean temperature riseof 140 °C and a maximum temperature rise of180 °C.

Narrow stress graded so wood studs (less than 38 mm)

*The use of a suspended ceiling provided for the purpose of protec ng steel beams in lieu of cladding, orspraying them, is a very restricted applica on and will rarely be found in the domes c sector. Unfortunately,a number of proprietary products available for protec ng downlighters will have erroneously been testedto this standard, but these will not be suitable for ‘making good’ xed ceilings or suspended ceilingsused to provide protec on to ‘ mber’ joisted oors or other ‘domes c’ forms of construc on.


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Page 22

ANNEX C

Guidance on what cons tutes robust construc on

which iden es where unprotected4

downlightersmay be ed

When the installer wishes to t unprotecteddownlighters, it is necessary to establish theconstruc on in detail and ensure that the oor is ofone of the following construc ons;

a) First oor of two-storey house:

• the joists are solid mber not less than 43 mmthick and at no more than 450 mm centres, and

• the oorboards above are either tongue andgrooved so wood greater than 18 mm thick orare ght ng bu jointed so wood boardsfree from dead knots, or is ‘ mber’ based jointed ooring not less than 18 mm thick, and

• the ceiling consists of 12.5 mmplasterboard or ‘sound’ lath and plasterwith the ‘hooks’ in good condi on.

If downlighters are installed in a compartment oor

(or separa ng oor in Scotland – see Annex F), theymust be protected regardless of the construc on.

b) All other oors in a single family unit:

• As for the rst oor above, except bu jointedoor boards are not permi ed without an

overlay of medium density breboard (MDF),hardboard or plywood not less than 4 mm thick.

c) One hour re resis ng oors between ats:

• the joists are solid mber not less than 43 mmthick and at no more than 450 mm centres, and

• the oorboards above are either tongueand grooved so wood boards greaterthan 18 mm thick and free from deadknots, or is ‘ mber’ based jointed ooringof a similar minimum thickness

• the ceiling consists of two layers ofplasterboard, not less than 30 mm* thickfor non- re rated board or not less than

25 mm thick of re rated** board.

4Protected means downlighters that incorporate integral re protec on or which are edwith re hoods that comply with the guidance given in Annex E of this Guide.* Excluding any textured surface which should be removed locally prior to ng the luminaire** Type 5 to BS 1230 or Type F to BS EN 520


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Page 23

ANNEX D

Summary of the recommenda ons given in

na onal regulatory re safety guidance: The requirements given in Table 1 and 2 of thisGuide are the ‘recommenda ons’ made in theGuidance Documents published in support of therelevant regional regula ons. These GuidanceDocuments o er a prescrip ve solu on to the‘func onally’ expressed regula ons in the relevantregion of the UK. At the me of publica on, therelevant regional regula ons that deal with the resafety issues are:

England & Wales

The Building Regula ons 2000

• Approved Document BFire Safety (Volume 1)Dwellinghouses (2013 Edi on)

Scotland

The Building (Scotland) Regula ons 2004

• The Sco sh Building Standards TechnicalHandbook Domes c (2013)

Northern Ireland

The Building Regula ons (Northern Ireland) 2000,as amended

• Technical Booklet E, 2005

The above regula ons apply only to new build, orto major refurbishments (material altera ons) thatare no ed a er the dates given. Buildings alreadyconstructed and/or occupied will have compliedwith the regula ons and associated guidance inforce at the me of applica on.

These Guidance Documents would have expressedthe recommended re performance of the structurein terms of the test standards described in Annex B.


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Page 24

ANNEX E

Test procedure to evaluate the robustness of

downlighter re hoods

1. INTRODUCTION

This Annex provides requirements 5 that needto be sa s ed by a downlighter re hoodthat is considered to be ‘robust’ in both itsconstruc on and ng, and thereby meets therecommenda ons given in this Guide.

During installa on, in order not to compromise theperformance of the downlighter, it is essen al thatthe area immediately above the downlighter andthe re hood remains free from thermal insula on(see 7.9). Subsequent to its installa on, however,the re hood needs to demonstrate its ability toremain in place and resist crushing, that is to be

‘robust’ in the event of any applica on of thermalinsula on or other material by others.

2. SCOPE

The purpose of this test procedure is to assess the

ability of a downlighter re hood which has sa s edthe re test requirements of BS 476: Part 21: 1987to retain its mechanical stability over its working lifewhilst providing the requisite level of re protec onto the structure of the buiding from a downlighterlocated beneath.

3. TEST PROTOCOL

The test protocol is a two part test. The rst partdeals with the ability of the specimen re hoodto resist compression a er the applica on of theinsula on within the test frame. The second partdeals with the ability of the re hood to resistdislodgement subsequent to installa on.

4. TEST EQUIPMENT

The test assembly is designed to simulate adomes c ceiling. It consists of two so wood oor joists 225 mm x 47 mm x 1500 mm long held450 mm apart, being screwed to similar sec oned

mbers at either end.

The base of the test construc on consists of a single

sheet of 12.5 mm type plasterboard nailed to theunderside of the mber framework. Two furthersheets of 12.5 mm plasterboard 1500 mm x300 mm are screwed to the inner face of the twomajor mber sec ons in a ver cal posi on.

Midway down the length of the frame, a holeis cut in the centre of the plasterboard on the

underside of the test frame. The size of the hole socut should be equal to that formed in the ceiling toaccommodate the downlighter that the re hood is

designed to protect.

A 1400 mm length of 400 mm wide mineral wool(24 kg/m 3) is cut su cient to provide an overallinsula on depth of 270 mm within the test frame.

The test assembly is held in posi on 2 m aboveground level by the use of appropriate sca olding.

5. TEST PROCEDURE

5.1 Compression test

The specimen re hood is located above the hole inthe manner prescribed by the manufacturer. Unlessthe device is iden ed as being suitable only forinstalla on from above, this will be posi oned frombelow.

Once the specimen has been located in posi on,the distance between the top innermost part of the

re hood and the lower surface of the plasterboardof the main structure shall be measured in at least 3

places, averaged and noted (a).

Once this has been ascertained, the insula ondescribed above is laid down the length of the testrig so as to be res ng on the upper surface of theplasterboard and specimen.

At this point, the distance referred to above will bemeasured again (b). The insula on shall remain inplace for 25 days. A er this period, the distancereferred to above will be measured once more (c).


25/28

Page 25

Once the above distances have been ascertained,

the insula on should be removed and the‘dislodgement test’ should be undertaken on thesame test specimen

5.2. Dislodgement test

One end of the test assembly will remainsupported via a ‘hinge’, whilst the opposing end isprogressively raised or lowered at a rate of 100 mm/sec un l either:-

a) the specimen re hood becomes dislodged, inexcess of the permi ed amount or

b) the test assembly reaches an angle of 45 degrees.

6. PERFORMANCE CRITERIA

6.1. Compression test

In the case of the second measurement (b), areduc on in the average distance of less than 5%, or5 mm (whichever is the smaller) is acceptable.

For any reduc on in excess of this gure, thespecimen is deemed to have failed. In the caseof the third measurement (c), there should be nofurther reduc on in distance measured.

6.2. Dislodgement test.

If the specimen moves laterally by more than10 mm or a gap of 3 mm appears between thespecimen and the top surface of the plasterboard

prior to, or on comple on of, the movement test,then the specimen will be deemed to have failed.

5 These test requirements have been developed by IFSA, the Intumescent Fire Seals Associa on.IFSA is a recognized trade associa on for manufacturers of intumescent materials and intumescent-based systems, membership of which requires all product claims to be substan ated.


26/28

Page 26

ANNEX F

Glossary of terms

Luminaire: equipment which distributes, lters ortransforms the light transmi ed by one or morelamps, and which includes all the parts necessaryfor suppor ng, xing and protec ng the lamps, butnot the lamps themselves and, where necessary,circuit auxiliaries together with the means forconnec ng them to the supply.

Cri cal applica on: An applica on where theconsequences of a failure to provide the reresistance requirements for an element will havea direct impact on the life safety of the occupants,e.g. between adjacent dwellings.

Compartment wall/ oor: known in Scotland assepara ng wall/ oor.

‘Modi ed’ re resistance: In domes c applica onsthe re resistance of the rst oor has a loadbearingcapacity of 30 minutes, but the integrity andinsula on criteria are reduced (modi ed) to only 15minutes.

House in Mul ple Occupa on: For England andWales, the legal de ni on of a House in Mul pleOccupa on is to be found in Sec ons 254-260 andSchedule 14 of the Housing Act 2004 or, in the caseof Scotland, the Civic Government (Scotland) Act1982 (Licensing of Houses in Mul ple Occupa on)Order 2000 as amended.

‘Separa ng oor and wall’: In Scotland, a ooror wall constructed to prevent the spread of rebetween buildings or parts of buildings of separatehabita on, such as ats and maisone es.

Three-storey house: A house in single occupa onwith two oors above ground oor levels, o enreferred to as a town house.

House of four storeys, or more: A house that hasthree or more oors above ground oor where theheight of the uppermost oor does not exceed18 m.


27/28

Page 27


28/28

The latest versions of all the BestPracticeGuides are available todownload from www.electricalsafetyfirst.org.uk

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Accuracy andconsistency

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Electricalinstallationsand theirimpact on the

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