FlameBlok: 'the single effective solution for housing associations'
August 2010
Fire alarms and sprinkler systems are what most people think of when they are asked to name fire safety features in a building. However, many don’t realise that it is what lies beneath that is equally as important.
David Deacon, General Manager of Cavalok Building Products, looks at why fire-rated PVC-U cavity closers are essential in maintaining the high safety standards expected of modern buildings.
“New buildings must be designed so that fires can be contained within the immediate area in which they started. This compartmentalisation prevents fire spreading to other areas of the building and is most commonly achieved using fire doors and fire-rated partition walls. However, in some buildings there are vulnerable areas which can bypass these ‘compartments’, allowing fires to spread rapidly. And when this is in a multi-occupancy facility the consequences can be catastrophic.
In many cases, it is the cavity wall that is the point of weakness, because it provides a continuous hidden path around the building, potentially spreading fire from one part of the structure to another without being detected.
One of the most vulnerable areas to fire transmission is therefore openings in cavity walls for window or doors. A BRE report conducted in 2005 showed that without appropriate detailing and protection fire can escape from a room into a cavity through the window junction in just under six minutes. This rapid spread endangers lives and demonstrates why we developed our FlameBlok range to provide over ten times the fire resistance of an unprotected detail.
The key to success in developing a cavity closer that would act as a fire barrier was to design it with a continuous strip of fire protection, including the corners of the frame, an area often overlooked. After design trials our technical team came up with the FlameBlok solution, offering fire performance all the way around a window. Before launching the product, we had it extensively tested and it was shown to prevent the spread of fire, by interrupting the cavity with a fire-resistant material in line with Part B of the Building Regulations (for both residential and non-residential buildings).
The tests were carried out by Chiltern International on cavity sizes up to 150mm, which means that FlameBlok can be used on buildings designed to meet higher environmental ratings. During testing, the timber frame failed before FlameBlok reached failure point, indicating that it easily exceeded the 60 minute rating required from cavity barriers as part of BS EN 1363.
With the FlameBlok cavity closer product outclassing traditional closing methods for both fire resistance and thermal performance we’re confident it is the single, effective solution for housing associations. Our fire-rated cavity closer remains the only product of its type in the UK made from 100 per cent post-consumer recycled PVC-U, whilst combining a one hour cavity fire barrier and cavity closer in a single product. This provides housing associations and contractors with a much simpler solution - because it means just one product closes the cavity and provides fire protection, eliminating the need for a separate fire sock. This saves labour over and above the savings already created by using cavity closers as a template for wall construction and ensures a safer, more thermally efficient building. It also makes a more sustainable building, as post-consumer recycled PVC-U reduces landfill and raw material consumption.
Fire-rated cavity closers are therefore an essential part of helping improve safety for building occupants during a fire, because they compartmentalise a building in a similar way to fire doors and fire-rated internal walls. Should a fire occur inside a building, it is these types of measures that reduce its spread. That’s because fire has a terrifying way of exploiting vulnerable areas - whether that is a staircase, a service duct in a wall or, as we all too often see, spreading unseen through the cavity wall. In each of these cases, the fire spreads rapidly, breaking out in far reaching areas of the building, before the occupants have had time to escape.
The only way to prevent fire exploiting these weaknesses is a joined-up approach between the various passive fire protection systems. When done in this way, building owners and managers stand the best chance of preventing the spread of fire, compartmentalising it in the area where it started, limiting the possibility of structural collapse. Ultimately, that means building occupants have the best chance of escaping and fire safety crews of quickly tackling the fire.”
