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22 April 2024

Passive Fire Protection in CLT Construction

CLT Floor Passive Fire Systems Test DIFC collars

Cross Laminated Timber (CLT) is becoming a popular construction product due to its range of physical characteristics and features. CLT is known for its sustainability factors with renewable timber plantations locking away carbon. Additionally, it is a light weight option, improving construction timelines.

CLT is used in commercial construction such as Tauranga City Council’s new office building by Warren and Mahoney and residential applications including Kāinga Ora developments.

When considering Passive Fire Protection (PFP) in a CLT construction it’s important to understand the properties of the substrate material. As a solid timber panel, CLT chars at a constant rate with the char increasing the thermal insulation of the panel providing a level of protection to the uncharred timber which retains its structural properties. Floors, ceiling and wall panels constructed into a ‘box’ create a fire cell, limiting spread to other cells.

Plumbing or electrical services that penetrate a CLT panel result in a hole in the fire cell for the service to pass through. The hole for the pipe or cables needs to have a PFP product applied to it to prevent the spread of fire beyond that fire cell. In the case of a fire, the pipe or cable will melt away and the heat will activate the PFP product which then blocks the hole. NZBC C3 AS2 requires PFP products to provide the same Fire Resistance Level (FRL) properties as the wall or floor system they are applied to.

Allproof’s products use an advanced intumescent that expands rapidly providing a stable char when exposed to heat, thus maintaining the integrity of the fire cell. The installation of the PFP product should be identical to the one tested to establish the Fire Resistance Rating.

Allproof are consistently developing and testing systems as the industry establishes new and common practices. There has recently been further testing to CLT walls and floors covering off common installations such as uPVC pipes, PEX pipes, Electrical cables and floor wastes, which can be applicable to shower tray applications.

Testing has been completed on 105mm CLT floor, 110mm CLT floor and 110mm CLT walls with results (FRL’s) achieving up to 60 minutes, -/60/60.

Products used are either fixed to the face of the exposed surface using fixings that penetrate deep into the substrate beyond the CLT char depth, or drop in from above and are secured from the unexposed face.

Testing is conducted regularly, meaning that new results are always becoming available. Please reach out for more information on selecting the correct PFP product for CLT walls and floors.

View more information on Allproof Industries, including contact details.
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