Complying with BR135 with RAINSCREEN DUO SLAB®

The Crofts - Completed project images - RAINSCREEN DUO SLAB and ROCKPANEL installed

Rainscreen cladding in buildings over 18 metres in height, present various challenges in complying with insulation requirements and fire safety standards.  Proximity to neighbouring buildings, provision of access for fire fighters, occupancy of the building and use of the building are some of the key factors to be considered in these types of buildings. Additionally, the height of the building is a key issue to be considered as it requires more time to escape from the top of the building to safety. This is a major challenge as it decreases the speed of evacuation and can also put wheelchair users at risk.

External cladding systems, such as the cavities within the external wall and the cladding material offer a potential route for fire spread through multi-storey buildings. The flames within the cavities can extend 5 to 10 times their original length as no other outlets exist, spreading through window openings and impinging on other parts of the building, usually above.

Careful planning of the building design and fire risk potential is therefore essential to ensure that the buildings achieve the required levels of fire safety and comply with BR135 standards. 

Specifically designed for high rise buildings, RAINSCREEN DUO SLAB® is a dual density insulation board that is manufactured from volcanic rock and comprises of a robust outer surface and a resilient inner face. By compressing the primary fleece onto the top 15mm of the insulation, the product can be used, unprotected, in conditions of severe climatic exposure, including strong wind and rain as experienced at high altitudes.

RAINSCREEN DUO SLAB® complies with Approved Document B, achieving the highest Euroclass classification: A1. As it is made from stone wool, it is naturally fire resistant and offers impressive non-combustible properties.

The robust outer surface of the RAINSCREEN DUO SLAB® resists damage and over-driving of fixings. As a fibre based product, it can be amalgamated to slot into very tight spaces and around brackets, leaving no empty gaps and achieving optimum thermal performance while also maintaining its shape in the long term by not moving, shrinking or warping.

ROCKWOOL RAINSCREEN DUO SLAB®’s unique dual density technology requires fewer fixings compared to standard stone wool slabs, thus providing an efficient and cost effective solution in over cladding applications. The product’s improved technology protects the slab against UV rays and provides high resistance to wind and rain thanks to its robust outer layer. When installed, RAINSCREEN DUO SLAB® knits together when tightly butt jointed, minimising heat loss.

Specifically designed for use in conditions of severe climatic exposure, ROCKWOOL RAINSCREEN DUO SLAB® has been successfully tested and approved by the Building Research Establishment (BRE) confirming its ability to exceed the maximum UK basic wind speed of 56 m/s. The slab’s versatility makes it an ideal product for use as a thermal insulation layer behind a variety of rainscreen cladding systems, such as ROCKPANEL.