What regulations apply to rainscreen cladding projects?
Understanding the relevant regulations for rainscreen cladding is crucial to ensure building safety, compliance, and long-term performance.
In a nutshell:
- Approved Document A ensures the structural integrity of a system throughout its lifespan.
- Approved Document B is concerned with fire safety and preventing the spread of fire.
- AD B stipulates the inclusion of fire-resistant materials and the use of cavity barriers to prevent fire spread.
- Approved Document C makes sure that a rainscreen system provides adequate protection against water ingress.
- Approved Document L focuses on carbon emissions by setting minimum energy efficiency standards.
- CWCT is a valuable resource for ensuring compliant, high-performing rainscreen cladding systems.
As beneficial as rainscreen cladding systems are, they can pose potential risks if not properly designed, installed, and maintained. Critical considerations include fire safety, structural stability, energy efficiency, and weather resistance. Regulations aim to mitigate these risks and ensure that rainscreen cladding systems meet minimum standards for safety and performance.
Structure (Approved Document A)
Approved Document A ensures that rainscreen cladding systems are designed and installed to withstand various loads (i.e. wind loads) and maintain their structural integrity over their lifespan. To comply with Approved Document A, rainscreen cladding must be structurally sound, taking into account wind loads, self-weight, fixing mechanisms, and impact resistance. Some of the methods to demonstrate compliance would be providing detailed structural calculations performed by a qualified structural engineer and ensuring that the substructure and fixings are assessed under BS EN 1991 and BS EN 1993 (steel structures) or BS EN 1995 (timber structures) as relevant.
Fire Safety (Approved Document B)
The Building Safety Act 2022 introduced new measures as part of AD B which focuses on preventing the spread of fire and ensuring the safe evacuation of occupants.
Regulation 7(2): Combustibility of External Walls restricts the use of combustible materials in external walls and materials must achieve specific fire resistance ratings (measured in minutes) based on building characteristics (use, height, location). For buildings over 18 metres (or 11 metres in Scotland) materials must be of limited combustibility (Class A2-s1, d0 or Class A1) or meet specific performance criteria demonstrated through large-scale fire testing (BS 8414). This extends to all components of the external wall, including the cladding panels, insulation and fixings.
Approved Document B also mandates the installation of compliant cavity barriers to prevent the spread of fire within the cavity behind the cladding.
Moisture Resistance (Approved Document C)
As we’ve covered previously, rainscreen cladding systems are designed to protect the building structure from the effects of the weather therefore the system must be properly designed to allow water that penetrates the cladding to drain or evaporate.
The purpose of Approved Document C is to ensure protection from moisture ingress. To guarantee compliance, the design must consider the risk of water penetration and condensation to prevent damp and mould. This risk is mitigated through the inclusion of effective ventilation.
Ways of demonstrating compliance would be providing manufacturer datasheets and certifications such as Centre for Window and Cladding Technology.
Thermal Performance (Approved Document L)
Part L aims to reduce carbon emissions from buildings by setting minimum energy efficiency standards. To adhere to Approved Document L, building elements (such as rainscreen cladding) must meet the minimum U- value requirement.
One of the standard methods of demonstrating compliance with AD L is through SAP (Standard Assessment Procedure). SAP is the government’s method for assessing and comparing the energy and environmental performance of dwellings, including its U-value and contribution to air tightness, which are inputted into models to assess overall building energy performance.
How to ensure compliance
To ensure compliance with your rainscreen cladding project, it is essential to adopt a collaborative, well-rounded approach. This includes selecting certified materials, involving industry experts from the outset, and conducting thorough risk assessments tailored to regulations. Adhering strictly to manufacturer guidelines during installation, scheduling routine inspections for ongoing safety, and staying up to date with evolving building regulations all play a vital role.
The Centre For Window and Cladding is a great resource for architects and contractors who are looking to specify compliant rainscreen cladding systems as they provide training and support for the industry.