Whitepaper Fire Safety
for External Wall Systems
>>>Please download our Whitepaper for realisation
of external wall systems completely in Euroclass A2
with Stamisol Safe One façade breather membranes.
Enhancing of fire safety for rainscreen façade systems
Since Dame Judith Hackett’s strong impulse with her report of Building a Safer Future, the industry has been working to implement a truly robust and assured approach to building the increasingly complex structures in which people live. More and more focus will be created on delivering the best quality building possible, in order to ensure that residents are safe, and feel safe. Let’s have a look, what this will mean for rainscreen systems in terms of fire safety and which risks have to be considered.
How can cladding be dangerous?
In fire safety terms, cladding can be dangerous in a few ways. Firstly, there is the makeup of the cladding system itself. If the cladding system in question contains combustible materials, such as expanded polystyrene (EPS) or polyurethane (PUR), then exposing these materials to a flame will result in fire spread on the outside of a building. This can occur through either a fire breaking out from one of the windows or doorways, through ventilation shafts or from a fire that has occurred on the outside.
Fire stopping measures are incorporated into nearly every cladding system – however, some are more effective than others. Many are made using mineral based materials, which are non combustible and highly effective at slowing the spread of fire around the outside of the building.
Rainscreen cladding systems require an open cavity to allow the insulation to “breathe” behind the weather resistant cladding panels – however, this is potentially dangerous in a fire, as it creates a chimney for the fire to spread vertically through the building. To allow this, most cavity barriers on the market now incorporate a strip activated by the application of heat which seals the cavity and when applied correctly dramatically slows the vertical spread of fire. This is called an intumescent cavity barrier.
What do building regulations currently say about cladding?
The building regulations were amended in 2018 to implement a ban on combustible building materials on the outside walls of buildings that are taller than 18 metres and contain more than one dwelling. This ban applies to residential housing tower blocks, hospitals, residential care homes, and student accommodation blocks.
So we are clear about the cladding, but what’s about the rear-ventilation level and products which are used in it, e.g. façade breather membranes?
Fire stopping measures are incorporated into nearly every cladding system – however, some are more effective than others. Many are made using mineral based materials, which are non combustible and highly effective at slowing the spread of fire around the outside of the building.
Specifying an Euroclass A2 classified breather membrane should form part of any overall facade fire strategy
To maintain the functionality of the insulation over a long period of time, facade membranes have UV protection and are used as a water-bearing layer and reliable weather protection. These are also open to diffusion in order to ensure the dehumidification of the building via the rear ventilation level.
What’s often not to be considered, is the fact, that facade membranes can cover a large area of the building envelope and form part of the crucial 'fire safety layer' within the external wall system, this can cause a high risk for fire safety if not supplied to a Euroclass A2-s1,d0 design. Addressing the issue of the right facade breather membrane should therefore form part of any overall facade fire strategy.
Whilst today, according to Approved Document B Regulation 7(2) vertical breather membranes are still exempt from A2 materials, which form part of an external wall. An essential reason is, that latest technologies with facade membranes in Euroclass A2-s1,d0 classification aren’t taken into account for these regulations.
A complete external wall system in Euroclass A2
With Stamisol Safe One facade breather membrane (classified Euroclass A2-s1,d0) it is possible to design a rear-ventilated external wall system completely in Euroclass A2.
It reliably protects against fire spread in the rear ventilation level and with minimum smoke during the evacuation process. It enables architects to combine maximume fire safety with a high degree of design freedom, even for open facade claddings - with up to 50 mm joints or an open area of up to 50 percent.
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>>>Please download our new Whitepaper with full technical documentation for realisation of external wall systems completly in Euroclass A2 with Stamisol Safe One façade breather membranes.