Sika® SolarRoof Design Guidance Policy for Solar PV Installations

Solar photovoltaic (PV) systems are becoming increasingly important as organisations transition to low carbon energy and seek long term reductions in electricity costs. Flat roofs are often well suited for PV installations due to their accessibility and unbroken surface area. However, the introduction of PV arrays can also influence how a roof system behaves in an external fire scenario. In the absence of comprehensive industry-wide regulations and testing, Sika’s approach is to seek to ensure that Sika SolarRoof and other PV installations maintain the required levels of building resilience and fire safety.

This guidance focuses specifically on mitigating fire spread and penetration on flat roofs utilising a Sika® SolarRoof PV System, a Sika® NatureRoof PV System, or any 3rd party PV System approved by Sika.  Note the addition of a PV System onto a Sika roofing system without prior assessment of compatibility and suitability by Sika will invalidate any guarantee.  

Measures relating to the electrical safety or prevention of PV related ignition sources are addressed separately under RC62 and related MCS PV electrical safety guidance.

1. Sika Design Principles

Unless a client requests an alternative approach in writing, Sika will only produce PV layout designs and roofing system specifications where at least one of the following conditions is satisfied.  These rules apply to new build, retrofit and refurbishment applications.


1.1 A 'Non-combustible' (BS EN 13501-1 class A2, s1-d0 or better) structural deck

Examples include:

  • Trapezoidal Profiled Metal decks
  • Concrete decks

 

1.2 A continuous 'non-combustible' (BS EN 13501-1 class A2, s1-d0 or better) layer above the membrane

Suitable options include:

  • A minimum 50 mm deep layer of 20/40 mm washed stone ballast, beneath the entire PV array area and extending a minimum 1.5m past the outside edge of the PV array, to help restrict potential horizontal fire spread across the roof surface
  • A minimum of 80 mm deep settled depth of Sika NatureRoof green roof substrate, beneath the entire PV array area and extending a minimum 1.5m past the outside edge of the PV array, to help restrict potential horizontal fire spread across the roof surface

 

1.3 A Sika-approved BS EN 13501-1 class A2, s1-d0 or better 'non-combustible' board (e.g., gypsum-based)

  • Installed between the insulation layer and the waterproofing membrane, beneath the entire PV array area, and extending a minimum 1.5 m past the outside edge of the PV array, to help restrict potential horizontal fire spread across the roof surface.  Where a transition occurs to a roof area without the non-combustible board, careful attention must be paid to ensure no unintended water damming or drainage falls impact occur

 

2. Additional Fire Mitigation Measures

In the absence of harmonised standards or recognised test methods for PV systems on flat roofs, Sika applies the following rules within its designs to reduce the risk of flame spread:

2.1 Separation Zones

Maintain a separation zone of 1.5m where achievable (minimum 1.0m) between the PV array and:

  • The external face of the perimeter or parapet walls
  • Rooflights
  • Upstands and penetrations
  • M&E plant or other equipment

 

2.2 Array Level Fire Compartmentation

  • Introduce a 1.5m fire break at least every 40m within large PV fields
     

These measures represent Sika's internal best-practice guidance, not mandatory industry standards.  Building Control officers, insurers, and project-specific risk assessors may have additional or alternative requirements depending on use class, insurer preferences, structural limits and building type.

3. PV Panel Selection

Only recommend the use of:

  • Euroclass A modules, or
  • Glass/Glass Modules (glass front and rear)

 

4. Maintenance Requirements

Appropriate maintenance is essential to ensure ongoing system performance and fire safety. Maintenance regimes will vary by PV panel and mounting type, but typically include:

  • Checks on the string connections to ensure they are installed in accordance with the manufacturer's instructions and there is no electrical arcing
  • Cleaning of the surface of the PV panel to remove any built-up dirt and/or bird droppings
  • Inspection of the PV panel surfaces for microcracking, and the removal and replacement of any damaged panels
  • Checks on any frame connectors, mechanical attachment and/ballasted mounting components
     

For BioSolar roofs:

  • Prevent vegetation encroaching into fire breaks
  • Remove dry thatch as part of seasonal maintenance


Project specific O&M requirements should be integrated into the building maintenance plan and implemented.

 

5. BioSolar (Green Roof + PV) Considerations

BioSolar roof systems, which integrate a green roof with PV arrays, provide sustainability benefits and can contribute to biodiversity net gain. To maintain fire safety the following guidelines should be followed:

5.1 Growing Media Requirements

  • A minimum 80 mm settled depth of growing media with ≤ 50% organic content is considered compliant under DCLG and GRO Fire Performance guidance (note, Sika substrates are peat-free and contain ≤ 20% organic matter, comfortably meeting these requirements)
     

5.2 20/40 mm Washed Stone Ballast Gravel Margins Within Green Roof Zones In Accordance With DCLG and GRO Guidelines

  • 500 mm wide × 75 mm deep where vegetation meets combustible vertical elements and/or opening doors/windows/rooflights
  • 300 mm wide x 75 mm deep where vegetation meets non-combustible vertical elements, non-opening doors/windows/rooflights, and at roof penetrations i.e. SVP's and rainwater outlets
  • On large roofs, include 1.0m fire breaks at 40m intervals
     

4.3 Referenced Guidance

The GRO BioSolar best practice guide offers additional design considerations for PV integrations within BioSolar roof systems.

6. Scottish Building Standards - Considerations for Flat Roof PV

Scottish Building Standards sometimes request PV modules using 4 mm glass. This originates from clauses that apply to roof coverings for pitched installations. For flat roofs:

  • PV modules mounted above the waterproofing do not replace the roof covering
  • Therefore, the criteria for low/medium vulnerability in the roof covering classification generally do not apply to above roof systems


Where Building Control still requires mitigations, the following options may be accepted:

6.1 Panel Selection

  • Use Euroclass A modules, or
  • Modules with 2 mm glass front and rear (4 mm combined)


6.2 Non-Combustible Deck

  • Concrete or metal decks typically satisfy most queries without further modification


6.3 Hard Landscaping / Ballast

  • If required, a ballast layer can be installed beneath and around the array, extending ≥ 1.0m beyond its perimeter
  • In such cases, a non-combustible insulation material is not usually necessary beneath the array provided the ballast adequately prevents flame spread and penetration

7. Supporting References

Sika recommends reviewing the following industry sources for wider context on PV fire safety:

  • Industry papers comparing insulation performance under PV loading
  • Fire Protection Association guidance relating to photovoltaic installations
  • Solar Energy UK O&M best practice documentation