FIS-BP-Guide-Through-Wall-SFS

BEST PRACTICE GUIDE THROUGH-WALL INFILL STEEL-FRAMED SYSTEMS (SFS)

thefis.org steel-sci.com asfp.org.uk

BEST PRACTICE GUIDE THROUGH-WALL INFILL STEEL-FRAMED SYSTEMS (SFS)

FIS and SCI would like to thank the following individuals who have contributed to the production of the guide.

Craig Abbott FSI David Atkinson Voestalpine Metsec Yisheng Tian Ash & Lacy Mandeep Bansal Knauf Robert Cridford Etex Building Performance Alex Double ADDC Mike Foy Mansell Finishes Stephen Hall Hadley Group Kate Hawkins Stanmore Richard Haworth Saint Gobain Interior Solutions

Daryl Lewis Protektor Nicholas Mead Laing O’Rourke David Metcalfe CWCT Ross Newman Warringtonfire Dan Norman Obex Phil Pettinger NHBC Andrew Richardson James Hardie Alain Speed PRP Architects

Andy Taylor ASFP Andrew Way SCI Richard Wilson Etex Building Performance (Employers correct as of June 2022)

Glenn Haughton Klasse Group Jon Jacznik Drywall Contracts Constantinos Kyprianou SCI

Apart from any fair dealing for the purposes of research or private study or criticism or review, as permitted under the Copyright Designs and Patents Act, 1988, this document may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the UK Copyright Licensing Agency, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organisation outside the UK.

Enquiries concerning reproduction outside the terms stated here should be sent to SCI or FIS at the addresses given on the back page.

Although care has been taken to ensure, to the best of our knowledge, that all data and information contained herein are accurate to the extent that they relate to either matters of fact or accepted practice or matters of opinion at the time of publication, SCI or FIS, the authors and the reviewers assume no responsibility for any errors in or misinterpretations of such data and/or information or any loss or damage arising from or related to their use.

FOREWORD

As the market for light gauge steel framing develops the language used to describe system develops with it, this is none truer than the case with infill external walling using steel framing systems (SFS). ‘Through-wall’ is a term being used to describe performance wall systems comprising of the frame and the plasterboards and sheathing bords as a minimum, but some systems go further and include the insulation and even the façade. This guide written by members of the FIS SFS working group, with help from the Steel Construction Institute and Association for Specialist Fire Protection, aims to explain the differences between the offerings and bring together in a single document the terms used to describe the elements that make them up. The guide also explains the importance of specifying, procuring, and installing the correct products to ensure compliance in this vital part of the construction process.

COLIN KENNEDY CHAIR, FIS SFS GROUP

FIS is the trade body representing manufacturers, suppliers and installers in the fit-out sector, including steel framed systems (SFS). The Steel Framed Systems Working Group is an inclusive body with the following objectives:

• Develop technical standards as required • Promote best practice in the market • Educate and inform clients and specifiers about (working group) work • Promote the products and skills of FIS members in this field • Monitor and support risk on behalf of the community • Shape the market so that the correct adherence to standards is recognised and adhered to by all, to the benefit of clients.

FOREWORD

The term ‘through-wall’ (with various spellings and abbreviations) has been in common use in the construction industry for many years now, but its precise meaning is still unclear for many people. This is not surprising as a recognised definition of ‘through-wall’ has not been provided up until now. This joint publication from FIS, SCI and ASFP addresses the need by providing a clear definition and presenting useful information about the topics and performance characteristics related to ‘through-wall’ systems. The leadership of FIS in driving this publication has been critical for achieving this new guide for the industry to utilise. Steel has become the market leading material for this application owing to its quality, speed of installation and design versatility. When correctly specified and installed through-wall systems, can provide the necessary fire resistance and weather tightness of the wall.

ANDREW WAY, ASSOCIATE DIRECTOR, SCI (STEEL CONSTRUCTION INSTITUTE)

“This joint publication from FIS, SCI and ASFP addresses the need by providing a clear definition and presenting useful information about the topics and performance characteristics related to ‘through-wall’ systems.”

FOREWORD

Understanding the impact of different component materials on the ability of a constructed system to perform, together with how the system interacts with the structure and any potential movement is fundamental to the delivery of a successful installation. Future legislation, arising from the Building Safety Act, will require a much greater focus on designing elements of construction for submission to the Building Safety Regulator and keeping records within the golden thread. This guide helps to define through wall systems, the component parts within those systems and relevant performance characteristics. Understanding how these components work together in a system is vital, in order to avoid substitution or installation outside of the system requirements. It covers a number of important parameters when considering the reaction to fire and fire resistance performance of the through wall systems.

DR ANDREW TAYLOR, TECHNICAL OFFICER, ASFP (ASSOCIATION FOR SPECIALIST FIRE PROTECTION)

“This guide... covers a number of important parameters when considering the reaction to fire and fire resistance performance of the through wall systems.”

CONTENTS

INTRODUCTION. . . . . . . . . . . . . . . 7

Technical evaluations

SCOPE. . . . . . . . . . . . . . . . . . . . 7

Acoustic performance

Conservation of fuel and power

DEFINITIONS. . . . . . . . . . . . . . . . .8

Impact of load on the fixing: what can be added to the systems?

SYSTEMS. . . . . . . . . . . . . . . . . .11

System types

Interface of internal compartments with the external envelope

Evidence of performance and responsibility

Service penetrations

Specification

Design life/sustainability

Installation

Warranties

DESIGNPROCESS. . . . . . . . . . . . . .14

INSTALLATION. . . . . . . . . . . . . . .35

Road map for design

Tolerances

The golden rules

Benchmarks

Design checklist requirements

The four Cs process

APPENDIXA................ 37

Design guidance - further reading

Other relevant standards for through-wall

Junction detailing

Regulation 7

Interface with structure

Current legislation on fire performance (part B)

Z bars and cleats for fixing to structural steel

Regulation 38

Steel frame limiting temperatures

Concrete frame typical build-ups

APPENDIXB................42

Deflection head detailing

Impact of Building Safety Bill and Fire Safety Act

Façade systems

Impact of PAS 9980

Performance attributes and parameters

Structural Engineers Registration (SER) to structural performance

Building types

Fire performance

ACKNOWLEDGMENTS. . . . . . . . . . .43

Evidence of compliance

INTRODUCTION

This is an industry best practice guide and is designed to assist all persons involved in the design, procurement and installation of through- wall systems. It should be read in conjunction with the FIS and SCI Technical Report ED017 Design and Installation of Light Steel External Wall Systems and the FIS SCI Specifiers Guide – Light Gauge Steel Framing Systems (SFS) External Wall Systems.

thefis.org/membership-hub/publications/sfs-guide/

thefis.org/membership-hub/publications/specifiers- guides/light-guage-external-wall-systems/

SCOPE

This guide has been produced to provide a standard definition of through-wall and assist in the design, specification and installation of SFS through-wall systems. This includes infill systems but does not include continuous systems.

• Manufacturers • M&E contractors • Owner/occupiers • Principal contractors (main contractors) • Principal designers • Residents • Site managers • Specialist penetration seal contractors • Specifiers • Supervisors

The guide is based on Building Regulations in England at the time of writing. However, guidance relevant to Scotland, Northern Ireland and Wales is provided in this document. This best practice guide has been produced to assist in the design, specification and installation of through-wall systems and is aimed at: • Architects • Building control bodies • Building owners • Building safety managers • Clerks of works • Competent persons

The responsibilities of individuals or organisations for the design and integration of through-wall into the structure are described in the CDM Regulations and the proposed Building Safety Bill. Duty holders should familiarise themselves with their duties and responsibilities and competencies.

• Consultants • Contractors • Contractors with a design portion • Fire engineers • Insurers

DEFINITIONS

Compartment (fire) 2 A building or part of a building, comprising one or more rooms, spaces or storeys, that is constructed to prevent the spread of fire to or from another part of the same building or an adjoining building. Compartmentation 2 A means of preventing the spread of fire within a building and providing adequate means of escape by containing it in the compartment of origin. Designer An organisation or individual who prepares or modifies a design or who arranges or instructs any person to do so. HSE CDM Designers hse.gov.uk/construction/cdm/2015/designers.htm Dewpoint 1 Temperature at which air becomes saturated with water vapour. Fire classification Reaction to fire classification is determined in accordance with BS EN13501-1 Fire classification of construction products and building elements - Part 1: Classification using data from reaction to fire tests. This considers how a product or element behaves in the early stages of a fire (ignition and growth), and how a material might contribute to the development of that fire (ignitability and combustibility). The classification standard details the test methods used, and performance levels expected to achieve a reaction to fire classification. The classification system has seven classes from A1 (products that do not contribute to the development of a fire) to F (products with no performance criteria claimed). Fire resistance classification considers the ability of a system to resist the effect of a fully developed fire, and prevent the passage of fire through a wall/ floor, and/or the ability to keep structural integrity. Fire resistance classification is determined in accordance with BS EN13501-2 Fire classification

Assessment A technical evaluation of the likely performance of a component or element of structure (as defined in Approved Document B and equivalents in Scotland, Wales and Northern Ireland) if it were to be subjected to a relevant standard fire test. An assessment may consider design changes to a tested element of construction for a specific project, or it could form a wider scope of approval with a defined period of validity. Assessments, based on sufficient relevant test evidence, provide a defined scope of approval for a particular design or range of designs. They form an opinion of the likely performance of a component or element of structure if it were to be subjected to a standard fire test. AVCL 1 Air and vapour control layer – a continuous layer of impermeable material. Breather membrane A membrane with water vapour resistance greater than 0.25 MN·s/g and less than 0.6 MN·s/g. Building control body (BCB) 3 The body responsible for enforcing Building Regulations on a project and assisting with compliance by giving feedback on plans and providing site inspections. This may be a local authority building control officer or an approved inspector. Cavity barrier 2 Construction within a cavity, other than a smoke curtain, to perform either of the following functions: • Close a cavity to stop smoke or flame entering • Restrict the movement of smoke or flame within a cavity. CDM Regulations 2015 2 Regulations intended to protect persons from health and safety risks from construction work through a systematic framework for the management of those risks.

DEFINITIONS

Penetration 2 An aperture with one or more services passing through. Penetration seal 2 A system used to maintain the performance of a separating element at the position where one or more services pass through or where there is provision for services to pass through a fire-separating element. Principal designer An organisation or individual (on smaller projects) appointed by the client to take control of the pre- construction phase of any project involving more than one contractor. HSE CDM Principal Designer hse.gov.uk/construction/cdm/2015/principal-designers.htm Relevant buildings Defined in Regulation 7(4) of Approved Document B in England Fire Safety: Approved Document B gov.uk/government/publications/fire-safety-approved- document-b R-value R-value (also known as thermal resistance) is the measure of how well a particular thickness of material resists heat transfer through thermal conduction . System owner 2 Person or organisation who owns the performance evidence of a system.

of construction products and building elements - Part 2: Classification using data from fire resistance tests. Fire resistance classifications are usually quoted as a function of the time period for which fire resistance has been proven, together with the classification indices R (loadbearing capacity), E (Integrity) and I (insulation performance). Fire-separating element 2 A compartment wall, compartment floor or construction that encloses a protected escape route and/or a place of special fire hazard. Helping hand bracket A cladding support system that typically consists of ‘helping hand’ brackets fixed to the substrate at set vertical and horizontal separations. Intumescent 2 A reactive material that, when heated, expands to maintain the penetration seal. Reactive fire protection material 4 Reactive materials specifically formulated to provide a chemical reaction upon heating, such that their physical form changes to provide fire protection by thermal insulative and cooling effects. Loadbearing wall 5 Wall designed to support a vertically applied load.

Membrane 1 A thin layer of material.

Sheathing board A layer of board that forms the outer SFS wall assembly.

Non-loadbearing wall 1 Wall designed not to be subjected to any load other than its own weight. Passive fire protection 2 A product or system that provides protection to the building and occupants without further change or requirement for activation or motion – for example, fire-resistant drylining.

Through-wall A series of components that, when tested together, can provide evidence of compliance. Considered to be from the inner plasterboard lining to the sheathing board, fixed to a light gauge steel framing, sometimes this will include the insulation on the face of the sheathing board.

DEFINITIONS

1 Passive Fire Protection Forum (PFPF) Guide to Undertaking Technical Assessments of Fire Performance of Construction Products Based on Fire Test Evidence 2 BS 5250 3 Firestopping of Service Penetrations – Best Practice in Design and Installation

U-value 6 U-value (or thermal transmittance co-efficient) is a measure of how much heat will pass through one square metre of a structure when the temperatures on either side of the structure differ by 1ºC (expressed in W/m2K). Note: the lower the U-value, the more effective it is at preventing heat transfer. Relevant building Extract from Fire Safety for Relevant Buildings - Guidance Notes: “(a) a “relevant building” means a building with a storey (not including roof-top plant areas or any storey consisting exclusively of plant rooms) at least 18 metres above ground level and which— contains one or more dwellings; contains an institution; or contains a room for residential purposes (excluding any room in a hostel, hotel or boarding house); and (b) “above ground level” in relation to a storey means above ground level when measured from the lowest ground level adjoining the outside of a building to the top of the floor surface of the storey.” labcwarranty.co.uk/fire-safety-for-relevant-buildings- guidance-notes/ Weather and airtight membrane A flexible seal used between windows and the external wall construction; sometimes manufactured from ethylene propylene diene monomer (EPDM). EPDM is not suitable for use in a relevant building because it does not meet the minimum B-s3, d0 classification.

4 BS EN 13381-8:2013 5 BS EN 13501-2:2016 6 Scottish Building Standards handbook

SYSTEMS

OPTION 3 Through-wall plus façade

SYSTEM TYPES Through-wall is a relatively new term used to describe a system approach to external wall systems using light gauge steel framing, plasterboard, sheathing boards and breather membranes, and may include AVCL membranes as necessary. SFS light gauge steel framing systems provide the structural framework for the inner skin of external walls. An SFS/system supplier’s definition will be subject to the scope of their supply. For the purposes of this guide, through-wall is defined using the following three approaches: Option 1 From the inner plasterboard lining to the sheathing board Option 2 Includes the insulation on the face of the sheathing board Option 3 Includes the façade system. Note: in relevant buildings, work will be carried out so that materials that become part of an external wall, or specified attachment, of a relevant building are of European Classification A2-s1, d0 or Class A1, classified in accordance with BS EN 13501- 1:2007+A1:2009 – Fire classification of construction products and building elements. EVIDENCE OF PERFORMANCE AND RESPONSIBILITY System owners offering the options listed above carry out extensive testing in order to provide evidence of performance. Where a designer selects an option 1 system, they become responsible for the addition of external insulation, AVCL and the façade system working together. Where a designer selects an option 2 system, they become responsible for the addition of the façade system working together. Option 3 will have performance evidence of all the performance elements working together, which can be used to demonstrate compliance.

OPTION 2 Through-wall including insulation

OPTION 1 Through-wall

AVCL

Breather membrane

Through-wall including external insulation and façade.

Image: encon.co.uk/kingspan-k- roc-rainscreen-slab!pd-73-4762

SPECIFICATION The most common methods used by designers for the selection and specification of through-wall systems are noted below. Collaboration and communication are key to a compliant specification. It should be noted that any changes made to the specification at any stage will turn whoever makes those changes into the designer. Points to considerwhen writing a specification: • Talk to the manufacturer • Performance is king (fire, acoustics etc) • Consider the interface with other elements • Understand the use, now and in the future • Understand the budget • Understand the programme and site conditions • Understand the vision and client aspiration • Ensure that the performance and workmanship requirements and standards are clearly included • Understand the implications of maintenance • Understand the environmental implications and what will happen at end of life • Do not be scared of specifying new products.

SYSTEMS

A good specification should be developed with competent people from: • Manufacturers/suppliers • Architect/designer • Specialist installer • Fire engineer • M&E consultants. The specification should include (the following list is not exhaustive): • Product name and reference • Detail references • Performance requirements and supporting evidence • Field of application

• Structural performance • Environmental conditions • Movement accommodation • Substrate specification • Sample mock-ups and quality benchmarks • Tolerances • Thermal performance • Humidity • Air permeability • Acoustic performance • Life expectancy and durability • Third-party certification • Colour • Manufacturer’s details • Special instructions • Protection from damage during construction phase • Installation (suitably competent installers) • Inspection and preparation.

Analyse product datasheets, labelling, supporting docs etc.

Source alternative product

Suitable for application?

More info needed

Contact manufacturer for certified scope of application, ETA, test report or assessment

Sufficient data?

Obtain components

Install as per installation

instructions, data sheet, supporting docs etc.

Guidance on product selection

SYSTEMS

INSTALLATION Through-wall systems may be installed by multiple contractors rather than a single contractor, and are commonly installed by the following contractors: • Specialist SFS framing contractor • Specialist drylining contractor • Specialist window/door contractor • Specialist façade contractor.

through the walls or ceiling, which could contribute to mould formation, structural damage, heat loss and increased energy costs. Effective sealing of the building envelope requires effective workmanship, the right choice of AVCL and good detailing. Water vapour, which can find many ways into the construction, from wet trades to occupier activity, is difficult to control and could result in risks to the building and its occupants. Any AVCL should be airtight. The degree of vapour diffusion, however, depends on the material composition. It can be distinguished by four different product technologies: solid polyethylene membranes, typically with high and fixed Sd-values; composite AVCL membranes with low to medium fixed Sd-values; reflective AVCL; and smart AVCL with adaptable Sd-values by means of humidity concentration. Further guidance can be sought from BS 5250: 2021 Management of moisture in buildings – Code of practice. See Specfinish May 2, 2014. specfinish.co.uk/insulation-air-and-vapour-control-in- modern-buildings/ “Effective sealing of the building envelope requires effective workmanship, the right choice of AVCL and good detailing.”

The designer should consider all these parameters during the design stage:

BREATHER MEMBRANES If these membranes are part of the certification, they cannot be substituted or removed. Breather membrane performance: • Located in the cavity to prevent water

penetration into the inner leaf • Has high vapour permeability • Typically requires UV resistance

• Other performance characteristics to BS EN 13859-2 Flexible sheets for waterproofing. Definitions and characteristics of underlays. Underlays for walls • Reaction to fire B-s3, d0 or better in relevant buildings (From B4 of Approved Document B 10.15a Volume 1: Dwellings). AIR AND VAPOUR CONTROL LAYER (AVCL) AVCL performance: • AVCL should be located on the warm side of insulation • Has low vapour permeability • Other performance characteristics to BS EN 13984 Flexible sheets for waterproofing. Plastic and rubber vapour control layers • Reaction to fire B-s3, d0 or better. WHY IS AN AVCL IS NECESSARY? An AVCL has two basic functions: controlling the amount of vapour that travels through the building envelope; and providing an airtight seal when properly installed and maintained. Various studies show that an AVCL is necessary to prevent moisture from the interior migrating

DESIGN PROCESS

The main sections of this guide provide guidance on actions that should be carried out during each of the stages 1 to 7, as defined in the RIBA Plan of Work. These are illustrated below, together with stage 0, which is not covered in this guide as no decisions relating to through-wall are made at this stage.

The outcome here may be the decision to start a project.

Projects span from stages 1 to 6.

Stage 7 covers the ongoing use of the building.

Projects span from stages 1 to 6.

ROAD MAP FOR DESIGN

RIBA STAGE 2 - CONCEPT DESIGN

Prepare concept design including outline proposals for structural design. At this stage, the form of construction will be established, including through-wall if appropriate. Early-stage U-value calculations will be undertaken to establish appropriate wall thicknesses, typically undertaken by an insulation manufacturer, based on assumed depth for the SFS. RIBA STAGE 3 – SPATIAL COORDINATION Prepare developed design including coordinated and

Through-wall design development summary to RIBA Plan of Work 2020 stages:

RIBA STAGE 0/1 STRATEGIC DEFINITION, PREPARATION AND BRIEFING

Design consultant client appointments should include a design responsibility

matrix (DRM) giving an overview of their design responsibilities and which packages will be subject to contractor’s design portions (CDP). Where design consultant appointments occur at a later stage – for instance, when appointed by a contractor to provide design services in connection with a design and build contract – the DRM may be established or renegotiated at stage 3 or 4.

updated proposals for structural design. If not already undertaken, the design team should engage at

this stage with a through-wall manufacturer where specified and establish full performance

DESIGN PROCESS

requirements. Certification and classification reports, demonstrating tested performance meeting the project brief, should be obtained by the designer for any specified products and systems. Planning applications are usually made in stage 3. A fire statement should be submitted for applicable buildings in accordance with Gateway 1 planning requirements. This should include a description of the proposed construction and fire performance requirements. Some stage 3 functions are now being undertaken in stage 2 to provide a firm technical base for the concept design and to develop the early-stage fire strategy.

calculations (such as resistance to wind load), installation details and any additional information required by the employer’s requirements.

RIBA STAGE 6 – HANDOVER

Manufacturers’ technical departments should be consulted at the earliest opportunity to obtain copies of all evidence required to be

handed to the building owners as part of the Regulatory Reform (Fire Safety) Order (RRFSO) and Regulation 38.

RIBA STAGE 7 – USE

RIBA STAGE 4 – TECHNICAL DESIGN

In the majority of projects, the design team and construction team will have no stage 7 duties to undertake. The Plan of Work also

Prepare technical design in accordance with the DRM. At this stage, the specification or any contract particulars should include the level of CDP, which will

mentions other functions: • Implement Facilities Management • Asset Management • Undertake post-occupancy evaluation of building performance in use • Verify project outcomes including sustainability outcomes.

inform how far the designers take the design and what design completions are undertaken by the contractor. If a contractor has been appointed at this stage, early discussions with specialist subcontract installers can commence. A submission for Building Regulations approval should include either performance or proprietary specification for through-wall and include certification and classification reports for specified systems. Once the Building Safety Act is implemented, Gateway 2 requirements must be complied with for applicable buildings. Through- wall infill SFS is a series of components that, when tested together and installed as tested, can provide evidence of fire performance. There should be no substitution of components without the system owner’s written approval.

RIBA STAGE 5 – MANUFACTURING AND CONSTRUCTION

CDP is typically applied to the through-wall package, or to the SFS package when through-wall elements are procured separately. The contractor submits

verification of the system selected, any

DESIGN PROCESS

THE GOLDEN RULES The nine Golden Rules (GRs) provide guidance for designers of a process to ensure a compliant design of the through-wall infill SFS systems read against the RIBA Plan of Work referenced. It should be noted that some of the Golden Rules apply more than once against each of the RIBA Plan of Work stages. The system owners should be engaged as early as possible in the projects to ensure a compliant specification, design and installation.

GOLDEN RULE 1

GOLDEN RULE 2

GOLDEN RULE 3

Ensure an early engagement with system owners and

Review the fire strategy documents and fire

Identify all the performance requirements - fire, acoustic, thermal, weather resistance and

specialist installers.

strategy plans in conjunction with the M&E specifications.

loadbearing capacity - then establish the space required to install the through-wall.

GOLDEN RULE 4

GOLDEN RULE 5

GOLDEN RULE 6

Follow the ‘Design process for the through- wall’ and define the protection of the primary steel structure

Only select through-wall

Ideally select one system owner for the through- wall. Products from different manufacturers will need

systems which are tested using

the relevant standards or wall build-

and who is responsible. Building tolerances must be considered.

ups for which the combined components have relevant test/certification.

certified evidence to substantiate their use and performance.

GOLDEN RULE 7

GOLDEN RULE 8

GOLDEN RULE 9

Request copies of the evidence from the system owner. These should

Ensure the installers of ALL

Implement a structured

through-wall systems are

QA inspection plan to include photographic evidence as work proceeds.

be reviewed by a suitably qualified person to ensure the information is relevant to the situation.

suitably qualified eg on an approved list or certified.

DESIGN PROCESS

DESIGN CHECKLIST REQUIREMENTS Designers should provide the following information to the through-wall manufacturers, including plans, elevations and sections relevant to the project: • Reaction to fire classification to BS EN 13501-1 • Regulation 7 • Fire resistance – if different values for different directions of attack are required, please specify • Acoustic value – dB R w or R w +Ctr • Target U-value • Airtightness – Part L • Cladding type • System permissible thickness

standards where an independent test report will be produced. Designers should satisfy themselves that the specified products have evidence of compliance, with test reports from the relevant tests listed in this document or using third-party certification schemes. There are a number of industry-recognised third- party certification schemes that cover a wide range of through-wall systems. Independent third-party certification schemes formally assure the performance, quality, reliability and traceability of performance in systems and products. Products may also have third-party certification, which involves regular retesting factory controls and a scope of application. THE FOUR Cs CONSIDER the implications of where the product or system is being installed, its interface with the structure and other elements, if there are any through penetrations, partial penetrations or intersections. CLARIFY the potential impact of another product intersecting, penetrating or interfacing and what test evidence is available/required. This should be with the system owner and other relevant third- party suppliers. CHECK what test evidence/third-party certification is required, with the design team and authority having jurisdiction. CONFIRM that the test evidence provided is relevant to that situation, is in date and addresses the system’s interfaces and parameters. It should also satisfy the requirements of the Building Regulations, standards, guides and the principal designer. Where current test evidence is not available, a suitably qualified and approved person (as defined in Section 6 – Requirement of assessors and reviewers of the PFPF Guide to Undertaking Technical Assessments of Fire Performance of Construction Products Based on Fire Test

• Minimum and maximum SFS heights • Primary structure (concrete/steel etc)

• Method of fire protection intended for the steel • Plan to maintain internal fire compartmentation • Additional performance and construction requirements from warranty providers such as the National House Building Council and Premier.

THE FOUR Cs PROCESS

The Four Cs process ensures that the products and systems being designed for the project have evidence of compliance relating to the specific detailing and interfaces. Clear evidence of performance should be obtained for all products and systems on a project as early as possible in the design stage. Products and systems are tested in isolation of the building fabric, intersections and interfaces. Systems that are an inherent part of a building’s fabric will have other products, systems and materials that intersect, penetrate and interface with them. Where this occurs, the designer and person responsible for the purchasing should use the Four Cs process below to clarify that they have the evidence to prove that when these interfaces occur, all the products will perform as required within the parameters of the required design. To show compliance, products and systems are independently tested in UKAS or equivalent test laboratories and facilities to relevant and referenced international (ISO), European (EN) and British (BS)

DESIGN PROCESS

DESIGN GUIDANCE – FURTHER READING

Evidence) should carry out an assessment. Assessments may be undertaken for a number of reasons as described in Approved Document B and equivalents in Scotland, Wales and Northern Ireland. The subscribing organisation undertaking assessments should hold adequate professional indemnity insurance that covers all of its activities relating to the issuing of assessments, as defined in section 4 of the PFPF Guide to Undertaking Technical Assessments of Fire Performance of Construction Products Based on Fire Test Evidence.

The Steel Construction Industry (SCI) and FIS have a freely available guide to the design and installation of light gauge steel external wall systems available on their websites, known as

Technical Report ED017 Design and Installation of Light Steel External Wall Systems thefis.org/membership-hub/ publications/sfs-guide/ This guidance encompasses all aspects of light steel external wall systems, from design to installation and from specification to sign-off.

Guide to Undertaking Technical Assessments of the Fire Performance of Construction Products

Based on Fire Test Evidence 2021 firesectorfederation.co.uk/wp-content/

uploads/2021/02/Guide-to-Undertaking-Technical- Assessments-of-the-Fire-Performance-of-Construction- Products-Based-on-Fire-Test-Evidence-2021-1-2.pdf Where an assessment is required to satisfy the requirements as described in Approved Document B, the Passive Fire Protection Forum (PFPF) Guide to Undertaking Technical Assessments of Fire Performance of Construction Products Based on Fire Test Evidence describes the method and competencies, should this be required. For any through-wall to be successful, there must be collaboration between all parties with adequate time allowed. This would include: • Designers: principal designer, architect, structural engineer, building services engineer and specialists such as access consultants and fire engineering consultants • Building control bodies • The principal contractor • Specialist through-wall contractors with design portion • M&E contractors • Product manufacturers – SFS, insulation, membranes, fixings, drylining, M&E services • The building owner • Quantity surveyors/purchasing teams.

The FIS/SCI P433 Specifiers Guide - Light Gauge Steel Framing Systems (SFS) External Wall Systems also helps specifiers understand the granular details involved in the design process and production of an SFS specification. thefis.org/membership-hub/ publications/specifiers-guides/light-

guage-external-wall-systems/

SCI P424 provides guidance on how light steel framing, which includes SFS, should be designed and detailed to provide fire resistance in accordance with the Building Regulations.

DESIGN PROCESS

JUNCTION DETAILING Suitable detailing of the junction between the through-wall system and the primary structural frame is an important part of the design process. This section presents some typical details and guidance on specific aspects to be considered. INTERFACE WITH STRUCTURE The detailing of the interface of the SFS with the structure will need to be considered and this could be: • A concrete slab • Structural steel that is fire-protected with a reactive coating • Structural steel that is board protected. Note: each of the above may include Z bars in cantilever.

Note: any encasement to structural beams that may be exposed to the elements during the construction phase should use weather-resistant boards. Cladding systems and their components will be routinely tested to establish properties such as watertightness, airtightness and resistance to wind load. Guidance on envelope sealing testing can be obtained from the Centre for Window and Cladding Technology (CWCT). Other options include: • Fixing directly into the steel beam – consideration must be made if interfacing with an intumescent painted (reactive coating) fire-protected beam • Fixing into Z bars or cleats that are fixed into the steel – consideration must be made if interfacing with an intumescent painted (reactive coating) fire- protected beam and how to fire protect the Z bars • Refer to the ASFP Advisory Note 18: ASFP Position on Installing Partitioning to the Underside of Structural Steel Sections Coated with a Reactive Fire Protection System. If the structural steel is not board-protected, consideration must be given to cold bridging and air sealing the beam to the through-wall interface.

Cavity barrier

Concrete

Fire protected primary steel structure

Insulation

Z BARS AND CLEATS FOR FIXING TO STRUCTURAL STEEL

Infill SFS including boards and framing

Cladding

Cavity barrier

Concrete

Generic detail of through-wall (steel frame)

Check with the system owner that fixing through fire protection boards, as illustrated above, is an acceptable approach when interfacing with the structural steel beams. Any potential movement/rotation of the head channels when the SFS is subjected to loadings such as wind could result in damage to the fire protection.

Cantilevered Z Bars used as a stand-off to structural beams with reactive coating

The designer should specify the method of fixing to the structure, and this should include the type and gauge of any Z bars or cleats. The designer may be

DESIGN PROCESS

the frame designer or the structural engineer. The grade of steel for the brackets and cleats should be confirmed and it may be that the items are manufactured from the same grade steel as the SFS, such as s390 and s450 grade and min Z275 coating. See SCI P433 for further guidance.

Items within the cavity, such as cavity trays, ducts, vents and weep holes, are now standard requirements on builds and the manufacturers should be consulted to ensure the fire performance of these items does not inhibit the fire performance of the building and meets the requirements for the reaction to fire classification. Note: the regulations in Scotland differ from England, Wales and Northern Ireland with regards to the requirements for cavity trays, which are now exempt from the regulations. See The Building (Scotland) Amendment Regulations 2022 legislation.gov.uk/ssi/2022/136/regulation/3/made The infill SFS is fixed from structural slab to structural slab. The framing may be flush, in bond or in cantilever from the slab edge, and this will require consideration when detailing the through- wall system. DEFLECTION HEAD DETAILING Check with the system owner that they have evidence for the deflection head detailing for fire resisting through-wall construction.

STEEL FRAME LIMITING TEMPERATURES

Designers should consider the limiting temperature of the structural steel in collaboration with the structural engineers when detailing the interface with the structural frame. This will inform the type and performance of the fire protection required, which may necessitate higher performance to ensure that the deflection capability of the external wall system is included in the calculation.

CONCRETE FRAME TYPICAL BUILD-UPS

Cavity barrier

Concrete

Insulation

Infill SFS including boards and framing

Cladding

Head track with slots to allow deflection at the head

Cavity barrier

Concrete

Generic detail of through-wall (concrete frame)

Note: Ccavity barriers are shown indicatively and may be open state or closed depending on the cladding type.

DESIGN PROCESS

FAÇADE SYSTEMS The choice and specification of façade system will impact the detailing of the through-wall system and should be designed with the manufacturers of the through-wall and cladding systems to ensure they will work together. Façade systems include : • Rainscreen cladding • Composite panel • Brick cladding • Brick slip • Insulated render • Timber cladding • Render on cementitious board. Note: cavity barriers should be considered as part of a system. Note: there are different requirements for cavity barriers for each of the devolved nations. The SFS infill walling forms a secondary structure that is fixed between the primary superstructure at floor and soffit. It is generally positioned at the slab edge, allowing insulation and external finishes to be installed continuously outside the main structural frame.

Though-wall during construction

Infill system

Ventilated rainscreen. Cavity barriers removed for clarity but would be required.

Images: sigmat.co.uk/building-products/sigmat-sfs/

Plasterboard

Studs

Sheathing board

Mineral wool insulation

Helping hand brackets

Jamb stud

Stone mineral wool insulation

Cill track

Façade finish

Slotted head track

Rail system

DESIGN PROCESS

Plasterboard

Studs

Composite panel. Cavity barriers removed for clarity but would be required.

Sheathing board

Mineral wool insulation

Jamb stud

Stone mineral wool insulation

Cill track

Composite cladding

Slotted head track

Plasterboard

Brick/masonry cladding. Cavity barriers and brick work support removed for clarity but would be required.

Studs

Sheathing board

Mineral wool insulation

Stainless steel brick tie channels

Jamb stud

Stone mineral wool insulation

Stainless steel brick ties

Cill track

Brick cladding

Slotted head track

Plasterboard

Timber clad. Cavity barriers removed for clarity but would be required.

Studs

Sheathing board

Mineral wool insulation

Timber battens

Jamb stud

Stone mineral wool insulation

Cill track

Timber cladding

Slotted head track

DESIGN PROCESS

PERFORMANCE ATTRIBUTES AND PARAMETERS Current legislation on the performance of a building, and the products and systems that construct it, are described in the following regulations: • Building Regulations • Building (Amendment) (Wales) Regulations • Building (Scotland) Regulations • Building Regulations (Northern Ireland) • Fire Safety (Scotland) Regulations • Fire Safety Regulations (Northern Ireland) • Regulatory Reform (Fire Safety) Order. Guidance and technical notes issued by each of the devolved nations are noted below. IN ENGLAND GUIDANCE IS DESCRIBED IN APPROVED DOCUMENTS (AD) • Structure (Approved Document A) • Fire safety (Approved Document B) • AD B Vol 1: Dwellings • AD B Vol 2: Buildings other than dwellings • Resistance to the passage of sound (Approved Document E) • Conservation of fuel and power (Approved Document L) • Approved Document L1A New dwellings • Approved Document L1B Existing dwellings • Approved Document L2A New buildings other than dwellings • Approved Document L2B Existing buildings other than dwellings IN SCOTLAND GUIDANCE IS DESCRIBED IN TECHNICAL HANDBOOKS • Building Standards Technical Handbook Domestic • Building Standards Technical Handbook Non- domestic IN WALES GUIDANCE IS DESCRIBED IN APPROVED DOCUMENTS (AD) • Structural Safety (Approved Document part A) • Fire Safety (Approved Document B) • AD B Vol 1: Dwellinghouses • AD B Vol 2: Buildings other than Dwellinghouses • Resistance to the passage of sound (Approved Document E)

• Conservation of fuel and power (Approved Document L) • Approved Document L1A New dwellings • Approved Document L1B Existing dwellings • Approved Document L2A New buildings other than dwellings • Approved Document L2B Existing buildings other than dwellings IN NORTHERN IRELAND GUIDANCE IS DESCRIBED IN TECHNICAL BOOKLETS • Structure (Technical Booklet D) • Fire Safety (Technical Booklet E) • Resistance to the passage of sound (Technical Booklet G) • Conservation of fuel and power (Technical Booklet F) • Technical Booklet F1 Dwellings • Technical Booklet F2 Buildings other than dwellings. Other fire safety guidance is given in: • BS 9999:2017 Fire safety in the design, management and use of buildings. Code of practice • BS 9991:2015 Fire safety in the design, management and use of residential buildings. Code of practice. In addition to fire performance, air and water tightness performance will also need to be considered.

BUILDING TYPES

Specific technical guidance standards and documents exist for the following building types:

RESIDENTIAL • Fire – AD B Vol 1 • Acoustic – AD E • Conservation of Fuel and power – AD L1A, 2A SCHOOLS • Fire – Building Bulletin 100 • Acoustic – Building Bulletin 93 • Environmental design – Building Bulletin 87

DESIGN PROCESS

HOSPITALS • Fire – HTM 05-02

FIRE RESISTANCE The requirement for fire resistance will be given in the devolved countries’ regulations and guidance. The period of fire resistance is determined in minutes and measured as integrity (E) and insulation (I). Integrity (E) The through-wall system should stop flames and hot gases from passing through the element for the specified fire resistance period. Failure is deemed to have occurred if flames or hot gases physically pass from one side of the element to the other during the fire resistance period. Insulation (I) Insulation refers to an element or system’s ability to limit the surface temperature rise above ambient on the non-fire side of the element to 140°C as an average, or 180°C as a hot-spot maximum, for the specified fire resistance period during which the fire side is exposed to a fully developed fire. Loadbearing (R) Loadbearing refers to an element or system’s capacity to resist collapse due to loss of structural strength caused by exposure to fire, or more specifically the heat generated by a fire. The element should remain structurally stable for the specified duration. Direction of fire test Because a through-wall system is asymmetrical, the designer should check that the fire test evidence is compliant for the project requirements – inside to out, outside to in. Reaction to fire Reaction to fire relates to the degree to which a product will contribute, by its own decomposition, to a fire under specified conditions. At the time of writing, the devolved regional guidance differed in its acceptance criteria. Classification of products is arrived at by using BS EN 13501-1. These classifications are determined by testing to BS EN 11925 part 2 Reaction to fire

• Acoustic – HTM 08-02 • Energy – HTM 07-02

COMMERCIAL • Fire – AD B Vol 2 • Acoustic – AD E • Conservation of Fuel and power – AD L2A, 2B The table on page 24 captures all the performance requirements for through-wall systems. The system owner is encouraged to publish their performance using the template in this table. Note: air permeability performance is an onsite test that includes windows, doors and air vents; the results will depend on how well these are sealed. The Centre for Window and Cladding Technology (CWCT) publishes guidance on sustainability, design, specification, construction and performance. cwct.co.uk/pages/welcome-to-the-cladding-forum FIRE PERFORMANCE Through-wall infill SFS is a series of components that, when tested together and installed as tested, can provide evidence of fire performance. There should be no substitution of components without the system owner’s written approval. REACTION TO FIRE AND FIRE RESISTANCE Reaction to fire and fire resistance are separate measures of fire performance but there is often confusion between the two. Fire resistance is the measurement of the ability of a system to resist, for the period of required fire performance, the passage of fire and heat from one distinct area to another. Reaction to fire is the measurement of how a material will contribute to the fire development and spread, particularly in the very early stages of a fire, when evacuation is crucial. Reaction to fire is classified under BS EN 13501-1. Fire classification of construction products and building elements - Classification using data from reaction to fire tests.

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