PREFAB + PRECAST: A FORMIDABLE DUO

With companies increasingly growing wise to the advantages of moving the building process off site and into a controlled factory environment, prefabrication has become the world’s most advanced method of construction.

Complementing this process and widely regarded as a highly advanced construction material, is precast concrete.

One area in particular in which precast concrete excels is fire protection. Despite the advances in fire protection and detection technology, building with a fire resistant material is still the best way to protect people, assets, and structures.

Current building codes require that resistance to fire be considered in the design of a building, so it is important to look at how our structures can have the optimum fire protection systems in place while using prefabricated concrete elements.

“Current building codes require that resistance to fire be considered in the design of a building, so it is important to look at how our structures can have the optimum fire protection systems in place while using prefabricated concrete elements.”
National Precast CEO, Sarah Bachmann

For optimum fire safety and to mitigate fire risk, a building should incorporate both passive and active fire protection.

What is Passive Fire Protection (PFP)?

While Passive Fire Protection is just that, passive, it’s continuously at work. An integral component of fire protection and fire safety, it’s designed to contain fires or slow the spread of fire through the use of fire-resistant structural elements, such as walls, floors, and coatings.

By using structural elements that are non-combustible and do not emit fumes when exposed to fire, a structure’s inherent design allows for the safe evacuation of a structure’s occupants and can save lives, assets, and the building itself, guarding essential structural components from the effects and the spread of fire. Precast concrete is a best practice choice in that regard.

WHAT IS ACTIVE FIRE PROTECTION (AFP)?
Conversely, Active Fire Protection includes systems that require action or motion to make them effective in the event of a fire. Examples include fire extinguishers, sprinklers, smoke and fire alarms, and emergency services. They are a reactive approach to extinguishing a fire; they essentially fight the fire. They require commissioning and ongoing maintenance to be effective.

PASSIVE FIRE PROTECTION (PFP):
Integral fire protection from a structure’s fire-resistant walls and floor, that control or prevent the spread of fire.

ACTIVE FIRE PROTECTION (AFP):
Action or motion triggered fire protection systems – such as sprinklers – that aim to extinguish a fire.

HOW IMPORTANT IS IT TO HAVE AN APPROPRIATE MIX OF PFP AND AFP?
It is extremely important. Tragically, sometimes non-fire rated materials get passed as fire-rated, and fail spectacularly. Or AFP systems like sprinklers or coatings fail, increasing the reliance on any PFP which might be offered by a structure. If that happens in a structure offering little PFP and there’s a fire, the results can be disastrous. So a mix of fire protection is imperative.

WHAT BENEFITS DOES THE OFFSITE MANUFACTURE OF PRECAST CONCRETE PROVIDE?
Precast concrete can not only play an important role in a structure’s PFP (passive fire protection), but the offsite manufacture of precast elements can further minimise fire risk during the construction phase on a building site.

“Precast concrete can not only play an important role in a structure’s PFP (passive fire protection), but the offsite manufacture of precast elements can further minimise fire risk during the construction phase on a building site.“
National Precast CEO, Sarah Bachmann

The ‘just in time’ delivery offers a faster method of construction and therefore the time that a structure’s AFP remains non-commissioned is minimised. With less activity on the site, less waste and less clutter from materials’ deliveries, comes less chance of a fire.

Even when commissioned, AFP systems have the potential to fail if not properly maintained. On the other hand, precast concrete requires minimal long-term maintenance and, because it is non-combustible, it is inherently fire resistant; meaning none of its’ constituents are flammable.

HOW IMPORTANT IS PFP DURING THE CONSTRUCTION PHASE? ARE THERE ANY ADVERSITIES WITH AFP THAT WE CAN LEARN FROM?
A building isn’t only susceptible to fire once inhabitants have moved in. The inferno at Sydney’s Barangaroo construction site in 2014 that almost brought Sydney to a standstill is an example of how critical PFP is, particularly during a building’s construction. Luckily, workers were at lunch when the fire broke out.

During construction, because any AFP systems are not yet commissioned, the need for PFP is important to minimise the spread of any fire. Only having AFP systems in place isn’t enough. A totally precast structure, where flooring has been fully cured and supported by non-combustible precast columns and beams, will always provide a greater level of fire protection.

WE KNOW THAT PREFABRICATION ENHANCES FIRE SAFETY CONTROL, BUT HOW DOES PRECAST CONCRETE, SPECIFICALLY, TAKE THIS TO ANOTHER LEVEL?
Concrete doesn’t burn; it’s that simple. Unlike organic building materials, precast concrete is inherently fire resistant with zero flammability on both internal and external surfaces. Additionally, precast concrete is not required to be treated, coated, or covered in order to meet fire requirements, potentially saving time and money when compared to other prefabricated alternatives.

Unlike buildings constructed with less fire-resistant products, a precast structure does not need to rely alone on active fire protection systems for its structural integrity. Often designed as a key component of a building’s passive fire protection, a concrete structure will also assist with the prevention of collapse through structural fire resistance— and the safety of inhabitants is therefore maximised.

Specifying precast walls, floors, beams, columns, lift shafts and stairways brings a building leaps and bounds ahead when it comes to fire safety.■

Sarah Bachmann, National Precast CEO.