SAFETY & SECURITY Seal the voids, stop the fires
Chris Hall of Siderise highlights the critical importance of fire stops in tall buildings and the considerations that specifiers need to bear in mind
it’s more vital than ever that they benefit from adequate passive fire protection. Smoke generated by fires in high-rise buildings can spread vertically throughout the building, even if the fire itself is contained within one unit.
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When the linear gap at perimeter edge between the floor and curtain wall is not properly sealed, flames and smoke can spread vertically to higher floors and horizontally to adjacent spaces. To avoid that, it is essential to properly install fire stops to maintain the compartmentation of the building.
Perimeter barrier firestops seal the gap between the edge of the compartment floor slab and the external curtain wall. Due to project designs and site tolerances, the size of this linear gap can vary, so the fire stop system needs to have a degree of dynamic movement capability – compression and recovery – in order to accommodate service- ability movement, and more significant movement under fire load. In addition, the fire stop system must match the period of fire resistance of the compartment floor.
Integrity & insulation
All firestop systems need to be tested to two performance criteria – integrity and insulation. Integrity refers to the ability of the system to prevent the passage of flame, smoke and combustible gases through and around the material or through joints in an assembly. Insulation refers to a measure of the increase in conducted heat transferred from exposed to unexposed surfaces of 180°
C rises above ambient.
These two criteria are critical in the development of curtain wall perimeter firestop products. The most effective products combine a number of material features – density, thickness, resin content, fibre structure and controlled compression – which together determine the resistance properties. When looking at the ‘integrity’ criteria, the
ADF OCTOBER 2017
s tall buildings are set to continue to play a significant role in meeting our housing and workspace needs,
material chosen must be impervious to the transfer of flame and gases, easy to install with minimal site management and accom- modate all real-world requirements at interfaces, joints and details. In order to meet the fire and smoke stop requirements in all external facade applications, Certifier Approved perimeter barrier and fire stop systems offer a combi- nation of performance, practical installation and service benefits. These systems offer fire rating options ranging from 30 minutes to five hours and accommodate void widths up to 1,200 mm. In addition to providing an effective seal against the passage of smoke and fire, the products can also form an acoustic barrier and plenum lining.
Key design considerations
Before specifying a fire stop, test evidence, demonstrating the product is capable of accommodating movement of a facade, needs to be examined. It is imperative that the installed seal is able to function effectively with due regard to all designed movement serviceability limits – curtain walling and cladding facade systems will deflect due to positive and negative wind loads as well as occupational live loads. The criteria are covered by EN 13116:2001. Typically, a project may stipulate that the curtain walling system may have the following allowable deflection limits: under the declared wind loads the maximum frontal deflection of the curtain walling’s framing members shall not exceed L/200 or 15 mm when measured between the points of support or anchorage to the building’s structure – in compliance with EN 13116. These factors may inevitably combine to preclude the suitability and therefore use of certain systems, such as high-density material slab products.
Installation
Perimeter barriers must be installed to provide horizontal compartmentation on each level, while vertical cavity barriers should be provided as a minimum to fall in line with any compartment wall and more
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Adequate compartmentation is a must in tall buildings (shown: Al Fattan Crystal Towers, Dubai)
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