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22 June 2017

Building Cladding Systems and Passive Fire Protection

A reputable construction company recently had an issue with passive fire protection for the building rain-screen cladding system on a prestigious project. Their approach emphasised that the timing of the installation was critical to the project plan as delays would have a knock-on effect to other trades. Passive fire protection of the outside of the building seemed to have been overlooked by the construction company as well as the cladding designer/contractor — as is often the case.

The rain-screen cladding design included cladding frame-work (with curtain wall) to be attached to the outside of the building and rain-screen facade panels to be fixed to the frame-work.

The Underlying Issue

The project had progressed to the extent that access to the void between the building and the curtain wall (on the inside of the cladding system, where the passive fire protection system was to be installed) was becoming an issue.

On the inside of the building, some of the levels had interior stud work in place and, on the exterior, some of the cladding system had been fitted. This indicated that the timing of the installation of passive fire protection had been overlooked by all involved.

We often find that it is assumed that 'the other party' is taking care of the installation of passive fire protection and as a consequence it is only at the 11th hour that this oversight is discovered.

Further complicating any passive fire installation was that the cavity between the building and the cladding system needed to be ventilated as part of the design of the cladding system. This necessitated mechanical fixings to secure the passive fire system in position.

Passive Fire Protection Solution Covers TWO Dynamics

The installation of the Potters Rainscreen Ventilated Fire Barrier by BOSS Fire, with a FRR of up to -/120/120 was proposed.

This system allows for a gap of between 25mm and 50mm for ventilation of the cavity, while simultaneously providing passive fire protection to the exterior of the building.

In the event of fire reaching the void between the exterior of the building and the inside of the cladding/facade system, the intumescent material facing the curtain wall would activate — closing the ventilation gap. The result of the closure of this gap would be to slow the spread of smoke and fire on the outside of the building, allowing time for the building to be evacuated.

Due to the mix of building elements to the exterior of this building and in some areas, limited access to install the passive fire system, three different types of mechanical fixings were used to accomplish the installation.

Learnings from this experience include:

  • Cladding system designers can include provision for the ventilation of the cavity, reducing the probability of future leaky buildings, while simultaneously making provision for passive fire protection.
  • Project managers could make provision for the installation of passive fire protection to the exterior of the building at an appropriate time, so as not to limit or impede access for the installers of the system. This may significantly reduce the cost of labour and equipment hire etc.
  • Architects and structural engineers could consider the inclusion of passive fire protection systems on the exterior of the building early in the design phase. In collaboration with fire engineers, designers of cladding systems and passive fire installation specialists, the appropriate systems can be included in the submissions for building consent (PS 1) stage.
  • Fire engineers could incorporate the necessary passive fire protection to the exterior of the building as part and parcel of the fire engineering report. In consultation with the architect, cladding system designers and all the engineering disciplines, there should be no reason passive fire protection to the exterior of building projects should be overlooked.

Passive fire protection could save lives!

Collaborative Consultation

We at Potters encourage the professions to engage with us as early as the concept stage of a project to discuss the numerous aspects of passive fire protection to the exterior of building projects. We may not have all the answers but can certainly make a constructive contribution to the collaboration process.

View more information on Potter Interior Systems, including contact details.
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