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Fire in Concealed Spaces: What Specifiers Need To Know

Guest writer, Tom Foster, senior product manager at Saint-Gobain Isover, explains the importance of cavity barriers in fire protection and the requirements they must meet to ensure new buildings are safe.

A report last year by the National House Building Council (NHBC), Fire in Cavities in Residential Buildings, highlighted the benefits of specifying high-performance cavity barriers for installation in new homes. This conclusion followed a review of real fire incidents and a series of 21 experiments that showed how quickly fire can spread within cavity walls and concealed spaces if cavity barriers aren’t in place.

These findings are echoed in Approved Part B (Volume 1 – Dwellinghouses) of the Building Regulations, which states that concealed cavities present “a greater danger than would a more obvious weakness in the fabric of the building”, due to the fact that any fire would be hidden. Cavity walls can provide a ready route for flames in the event of a fire, allowing them to travel quickly to unaffected parts of the structure before building users are even aware of the danger.

To comply with regulations, specifiers must select cavity barriers for new homes that offer at least 30 minutes’ fire integrity and 15 minutes’ fire protection. However, depending on the building type, its height and the presence of other fire safety solutions, such as sprinklers, specifiers may need to choose products providing up to 120 minutes’ fire integrity to give building users enough time to escape.

Choosing the right solution

Quite simply, cavity barriers are designed to fill all the concealed spaces within the buildings, including junctions between external walls, partitions, roofs, ceiling and floors, as well as around windows and doors. To perform correctly and contain a fire effectively, they must be the right size for the junction in question and installed according to the manufacturer’s instructions.

Stone wool and glass wool are common materials used in manufacturing cavity barriers. The first offers a high resistance to extreme temperatures, allowing it to meet the maximum fire protection requirements, but glass wool is more durable, lightweight, and provides more advanced compression properties.

Traditionally, specifiers had to choose between one material and the other, according to the most pressing needs of their project. However, there are now innovative solutions available that combine the benefits of the two materials. Isover’s ULTIMATE™ Cavity Barriers, for example, has the heat resistance of stone wool and the durability of glass wool, offering up to 120 minutes’ fire protection with greater resistance to wear and tear. They are also much easier to handle for contractors, making them easier to install correctly to maximise safety.

The issue of fire spreading within wall cavities is an important one, and the NHBC report was right to put the spotlight on it, but fortunately specifiers can help to manage the problem. By selecting simple solutions, like cavity barriers, and choosing those that are easier for installers to fit correctly, specifiers can significantly increase the safety levels of the building they are working on, minimising the risk of fire to the people using the development.

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SpecifiedBy Editor