Part B, BROOF(t4) & Gateway 2 Specialists | S1 Roofing Ltd

Flat Roofing Solutions for Fire Compliance

S1 Roofing Ltd supports clients, consultants, and principal designers by providing fully compliant, system-based roof solutions that include high-quality insulation products, reliable roof coverings, and effective waterproofing systems.

Speak to Our Design Team design@s1roofing.co.uk

Flat Roofing Solutions for Fire Compliance

Speak to Our Design Team design@s1roofing.co.uk

THE CHALLENGE

When considering building materials, it's essential to choose the right insulation products that not only enhance energy efficiency but also complement your roof coverings. Additionally, incorporating effective waterproofing systems can protect your structure from water damage while ensuring a long-lasting performance.

WHAT HAS CHANGED

Gateway 2 & Increased Scrutiny

Under Gateway 2, there is a clear shift:

From specifying insulation products and roof coverings

To demonstrating system performance

Roof systems must now:

Clearly demonstrate compliance with Approved Document B

Consider BROOF(t4) performance in context

Provide robust design information and justification for waterproofing systems

Compliance must now be evidenced, not assumed

Supporting clients and principal designers with fully compliant roof system design from concept through to Gateway 2 submission.

OUR APPROACH

WHAT WE CONSIDER

Gateway 2 & Increased Scrutiny

Under Gateway 2, there is a clear shift:

From specifying insulation products and roof coverings

To demonstrating system performance

Roof systems must now:

Clearly demonstrate compliance with Approved Document B

Consider BROOF(t4) performance in context

Provide robust design information and justification for waterproofing systems

Compliance must now be evidenced, not assumed

Supporting clients and principal designers with fully compliant roof system design from concept through to Gateway 2 submission.

CALL TO ACTION

IN-HOUSE DESIGN TEAM

Gateway 2 & Increased Scrutiny

Under Gateway 2, there is a clear shift:

From specifying insulation products and roof coverings

To demonstrating system performance

Roof systems must now:

Clearly demonstrate compliance with Approved Document B

Consider BROOF(t4) performance in context

Provide robust design information and justification for waterproofing systems

Compliance must now be evidenced, not assumed

Supporting clients and principal designers with fully compliant roof system design from concept through to Gateway 2 submission.

HOW WE SUPPORT GATEWAY 2

Gateway 2 Design Support

We assist with:

Compliance-led system design incorporating insulation products

Review of proposed build-ups including roof coverings

Identification of potential fire risks related to waterproofing systems

Supporting design information for submission

Helping ensure smoother approval and reduced risk

WHY IT MATTERS

Designing for Real Fire Behaviour

Fire doesn’t test insulation products, roof coverings, or waterproofing systems in isolation.

It tests:

The full build-up

The weakest point

The interaction between components

The safest approach is to design systems that minimise risk — not rely on assumptions.

PROJECT EXAMPLE

West King Street Redevelopment Overview A large-scale mixed-use development requiring a range of roofing systems across inverted and warm roof build-ups, including the Town Hall, terraces, and residential buildings. The project incorporated multiple roof types, including: Blue roof systems Green and biodiverse roofs Paved and ballasted roof areas The Challenge Deliver multiple roof coverings within a single development. Achieve compliant build-ups in line with fire safety expectations where required. Coordinate inverted and warm roof constructions. Integrate drainage, waterproofing systems, and finishes across varying roof types. Address areas with restricted build-up heights. Our Approach Delivery of the roofing strategy required close coordination across multiple systems, disciplines, and supply chain partners. Working closely with our supply chain partners, we developed fully coordinated, system-based roof build-ups tailored to each roof type. This collaborative approach enabled: Integration of multiple roofing systems within a single development. Coordination of waterproofing systems, insulation products, and finishes across varying build-ups. Resolution of design constraints, including restricted build-up heights. Alignment of system components to achieve a consistent and robust overall solution. This included: Integration of blue, green, and biodiverse roof systems. Paved and ballasted finishes across terrace and podium areas. Use of non-combustible insulation products where required. Incorporation of A2-rated VIP insulation solutions in constrained areas. Waterproofing systems designed as part of the full roof assembly. Focus was placed on: System performance rather than individual components. Coordination of junctions, interfaces, and penetrations. Compatibility between drainage, insulation products, waterproofing systems, and finishes. The Outcome A range of coordinated, system-based roofing solutions across the development. Effective resolution of height-restricted areas using high-performance insulation products. Integration of multiple roof types within a single, coherent strategy. Reduced design risk through coordination and system integration. This project demonstrates the importance of designing roofing systems as complete assemblies — not collections of individual products.

CALL TO ACTION

Need support with a fire-compliant roof system? Speak to our design team about: Part B compliance, BROOF(t4) considerations, and Gateway 2 submissions, all while ensuring the best insulation products and roof coverings are utilized for optimal waterproofing systems. Contact us at info@s1roofing.co.uk or request design input at design@s1roofing.co.uk.

Roofing System Solutions

We work with a range of established roofing systems and materials, including insulation products, to integrate them into fully designed roof build-ups.

Our role is not to promote individual products, but to:

Design compliant systems with effective roof coverings

Coordinate full roof assemblies

Ensure performance at the system level with reliable waterproofing systems

Every solution is developed based on project requirements, not predefined products.

Green Roof Systems

Design, Supply & Installation

We design, specify, and install green roof systems that are tailored to project requirements, integrating insulation products and waterproofing systems into the design.

These systems are developed as part of a fully coordinated roof build-up, aligned with fire performance, durability, and relevant industry guidance, including suitable roof coverings.

What is a Green Roof?

Green roof systems incorporate vegetation and growing medium above the waterproofing layer, providing:

- Sustainable drainage

- Thermal performance

- Biodiversity benefits

- Protection of the roof structure

Applications

- Podium decks and terraces

- Residential developments

- Commercial buildings

Fire Compliance & Guidance

Green roof systems are designed in accordance with recognized industry guidance, including:

- GRO (Green Roof Organisation) Code of Best Practice

- Relevant requirements of Approved Document B

- Consideration of external fire performance (e.g. BROOF(t4) where applicable)

Key considerations include:

- Fire break detailing at perimeters and penetrations

- Control of vegetation zones and maintenance

- Compatibility of the full roof build-up

Fire performance is determined by the complete system, not individual components.

Our Approach

We design green roof systems as complete assemblies, considering:

- Waterproofing and root barrier integration

- Drainage and irrigation

- Load-bearing requirements

- Junctions, interfaces, and penetrations

Where appropriate, we work with tested or certified system build-ups and align designs with project-specific requirements.

Blue Roof Systems

Sustainable Drainage Roofing Solutions

We design, specify, and install blue roof systems tailored to project requirements, ensuring integration with various roof coverings and insulation products.

These systems are developed as part of a fully coordinated roof build-up, aligned with drainage performance, structural considerations, and relevant industry guidance.

What is a Blue Roof?

A blue roof system is designed to temporarily store rainwater at roof level and control discharge rates, supporting sustainable drainage strategies. This helps to:

- Reduce peak water runoff

- Manage drainage capacity

- Support wider SuDS (Sustainable Drainage Systems) strategies

Applications

- Urban developments

- Podium decks and terraces

- Commercial buildings

- Projects with drainage constraints

Design & Guidance

Blue roof systems are designed in accordance with recognized industry guidance, including:

- CIRIA SuDS Manual (C753)

- Project-specific drainage strategies

- Relevant structural and waterproofing systems standards

Key considerations include:

- Storage capacity and flow control

- Structural load implications

- Drainage outlet design and overflow provision

- Integration with waterproofing systems and insulation products

Fire & System Performance

Blue roofs introduce additional complexity to the roof build-up and must be considered as part of the overall system design. We consider:

- Compatibility of waterproofing systems within the full build-up

- External fire performance requirements where applicable (e.g. BROOF(t4))

- Detailing at penetrations, outlets, and upstands

- Interaction between layers under both wet and fire conditions

System performance is determined by the complete build-up, not individual components.

Our Approach

We design blue roof systems as integrated assemblies, ensuring:

- Coordination between drainage, waterproofing systems, and structural elements

- Compatibility of materials and components, including insulation products

- Robust detailing at interfaces and penetrations

Where appropriate, we work with tested or proven system build-ups and align designs with project-specific requirements.

Podium Deck & Terrace Roofing Systems Paving, Finishes & Roof Build-Ups We design, specify, and install podium deck and terrace roofing systems tailored to project requirements. These systems are developed as part of a fully coordinated roof build-up, aligned with structural performance, drainage design, and relevant industry standards. What is a Podium / Terrace Roof? Podium and terrace roofs typically incorporate waterproofing systems, insulation products, and finished surfaces such as paving or landscaping above occupied spaces. Applications Roof terraces Podium decks Residential and mixed-use developments Commercial buildings Design & Standards Podium and terrace roofs are designed in accordance with recognised standards, including: BS 6229 – Flat roofs with continuously supported coverings BS 8579 – Inverted roof systems (where applicable) Project-specific structural and drainage requirements Key considerations include: Falls and drainage design Build-up configuration (warm or inverted roof) Load distribution and structural performance Integration of finishes such as paving or landscaping Fire & System Performance Podium and terrace roofs must be considered as complete systems. We consider: External fire performance requirements where applicable (e.g. BROOF(t4)) Interaction between waterproofing systems, insulation products, and surface finishes Void spaces beneath paving systems Detailing at perimeters, upstands, and penetrations System performance is determined by the complete build-up, not individual components. Our Approach We design podium and terrace systems as integrated assemblies, ensuring: Compatibility between all layers Robust detailing at interfaces Coordination with structural and drainage design Where appropriate, we work with tested or proven system build-ups aligned with project requirements.

Waterproofing Systems Design, Specification & Installation

We design, specify, and install waterproofing systems as part of complete roof build-ups, ensuring that all roof coverings are compatible with insulation products.

Systems are selected based on project requirements, performance criteria, and their compatibility with the overall roof design.

Systems We Work With

- Hot melt waterproofing systems

- Cold applied liquid systems

- Bituminous felt membranes

- Mastic asphalt

- Single ply membranes

Design & Standards

Waterproofing systems are designed in accordance with relevant standards and guidance, including:

- BS 6229 – Flat roof design

- Manufacturer guidance and system certification

- Project-specific performance requirements

Key considerations include:

- Compatibility with insulation products and finishes

- Integration within warm or inverted roof build-ups

- Detailing at junctions, penetrations, and terminations

Fire & System Performance

Waterproofing forms part of the complete roof system and must be considered in the context of:

- External fire performance where applicable (e.g. BROOF(t4))

- Interaction with insulation products and surface finishes

- Behaviour of the full build-up under fire conditions

Fire performance is determined by the system as a whole.

Our Approach

We select and install waterproofing systems based on:

- Project-specific requirements

- Compatibility with full build-up and roof coverings

- Long-term durability and maintainability

Where appropriate, we utilise tested or certified systems to support performance and compliance.

Non-Combustible Roofing Systems Designed for Fire Performance & Compliance We design and deliver roofing systems that prioritize non-combustible materials where required, aligning with current fire safety expectations. What is a Non-Combustible Roof System? Non-combustible systems typically incorporate materials achieving A1 or A2-s1,d0 classification. However, performance is not defined by materials alone; it is determined by how the complete roof system performs as an assembly. Regulatory Context Non-combustible systems are often required or considered in relation to: Approved Document B (fire safety), project-specific fire strategies, building type, and risk profile. Our Approach We design non-combustible roof systems by: prioritizing A1 / A2 rated materials where required, considering the full build-up including insulation products, addressing junctions, interfaces, and penetrations, and designing systems rather than selecting individual components. What We Consider Materials include cellular glass insulation, stone wool, and A2-rated high-performance insulation systems. System Integration involves compatibility with waterproofing systems, build-up configuration (warm/inverted roofs), and interface detailing. Fire Behaviour covers surface and subsurface fire interaction and potential fire paths within the build-up. Supporting Compliance We support clients and designers by: designing systems in line with Part B requirements, considering external fire performance where applicable, and coordinating full roof build-ups. Compliance is determined by system performance, not individual components, ensuring that our roof coverings meet the necessary standards.

Roofing System Compliance Matrix

This matrix outlines the key standards and guidance considered when designing and delivering roofing systems, including insulation products and roof coverings.

It is intended to support understanding of system performance and does not replace project-specific design, specification or statutory approvals.

Fire Performance & Regulatory Guidance

Requirement Standard / Guidance Application Consideration External fire performance BS EN 13501-5 (BROOF(t4)) Roof build-up Assesses fire performance of complete system under external exposure Reaction to fire BS EN 13501-1 (Euroclass) Individual materials Material classification only – not system performance Building Regulations Approved Document B Whole building Fire performance requirements for roofs and elements

Roof Design Standards

Requirement Standard Application Consideration Flat roof design BS 6229 Warm roofs Design, falls, drainage and construction Inverted roofs BS 8579 Inverted systems Drainage, insulation products and build-up configuration Structural design Project-specific All roofs Loadings, deflection and structural performance

Green & Blue Roof Guidance

Requirement Guidance Application Consideration Green roofs GRO Code of Best Practice Vegetated roofs Build-up, fire breaks, vegetation and maintenance Blue roofs / SuDS CIRIA C753 Drainage systems Water storage, discharge and flow control

Waterproofing & System Integration

Requirement Standard / Guidance Application Consideration Waterproofing systems Manufacturer guidance + BS standards All roof types Compatibility with full system Detailing Industry best practice Junctions & penetrations Interfaces, upstands and sealing

System-Based Design Considerations

Across all roofing systems, we consider:

Full build-up configuration

Junctions, interfaces and penetrations

Interaction between materials and systems

Surface and subsurface performance

Compliance is determined by the performance of the complete system, including waterproofing systems, not individual components.

BROOF(t4) Roofing Explained External Fire Performance of Roof Systems Understanding BROOF(t4) is essential when designing and specifying roofing systems, including insulation products and waterproofing systems, in line with current fire safety requirements. What is BROOF(t4)? BROOF(t4) is the highest classification for external fire performance of roof coverings and systems under BS EN 13501-5. It assesses how a complete roof build-up behaves when exposed to external fire conditions, including: Surface flame spread Fire penetration Burning debris It is a system test, not a product test. System vs Product Performance It is important to distinguish between: System Performance BS EN 13501-5 (BROOF(t4)) Applies to the entire roof build-up Product Performance BS EN 13501-1 (Euroclass) Class 0 ratings These relate to individual materials only, not how the roof performs as a system. Why BROOF(t4) Matters BROOF(t4) classification is typically required for: Unrestricted roofing applications Compliance with Approved Document B Roofs on residential and commercial buildings Specifying materials with good fire ratings alone does not demonstrate compliance. It is the performance of the complete system, including insulation products and waterproofing systems, that must be considered. Limitations & Considerations While BROOF(t4) provides a recognised method of classification, it is important to understand: Testing is carried out under specific conditions Not all build-up configurations are tested Junctions, penetrations and interfaces are not always fully represented This means system design remains critical. Our Approach We support clients and designers by: Designing roof systems as complete assemblies Considering external fire performance within the full build-up Prioritising non-combustible solutions where appropriate Working with tested or proven system configurations where available Where full-scale testing is limited, we focus on: Reducing uncertainty Eliminating risk where possible Ensuring robust system integration Key Considerations in Design When assessing roof systems, we consider: Full build-up configuration Compatibility of insulation products, waterproofing systems, and finishes Behaviour at junctions, upstands and penetrations Potential fire paths within the system Fire performance is determined by how the system behaves as a whole. Supporting Compliance We work alongside clients, consultants, and designers to support: Alignment with Approved Document B Consideration of BROOF(t4) requirements Development of coordinated roof build-ups Clear and robust design strategies Speak to Our Design Team If you are reviewing a roof specification or require support with fire performance considerations, we can assist. We design roof systems as complete assemblies — not collections of individual products.

Flat Roofing Solutions for Fire Compliance

Flat Roofing Solutions for Fire Compliance

Welcome to S1 Roofing Ltd

THE CHALLENGE

WHAT HAS CHANGED

OUR APPROACH

WHAT WE CONSIDER

CALL TO ACTION

IN-HOUSE DESIGN TEAM

HOW WE SUPPORT GATEWAY 2

WHY IT MATTERS

PROJECT EXAMPLE

CALL TO ACTION

Roofing System Solutions

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