From Past Catastrophes to Modern Technologies: How Recycled Wood Can Become a Safe and Sustainable Material for Future Constructions

by Marco Arezio

The use of recycled wood in construction is gaining increasing popularity, driven by growing interest in sustainability and the circular economy.

However, one of the most significant challenges associated with using wood, particularly recycled wood, is fire resistance.

This article will explore historical and modern techniques for improving fire resistance in wooden structures, with a specific focus on recycled wood.

History of Wood Use in Construction and Fire Resistance

Wood is one of the oldest construction materials, used worldwide for thousands of years. However, its vulnerability to fire has always been a concern.

In past eras, cities built primarily from wood were prone to devastating fires. One of the most famous examples is the Great Fire of London in 1666, which destroyed much of the city and highlighted the need for more fire-resistant building materials.

Over the centuries, various techniques have been developed to improve wood's fire resistance. Early solutions included the use of clay or plaster coatings, and later, wood was impregnated with mineral salts like ammonium chloride or borax. However, these techniques were not always effective or practical on a large scale.

With industrialization and the introduction of new building materials, wood lost ground to concrete and steel, which were considered safer in case of fire. However, with today’s renewed interest in wood, driven by its ecological properties, it has become crucial to develop modern techniques to enhance its fire resistance.

Characteristics of Recycled Wood

Recycled wood comes from various sources, such as old buildings, pallets, or discarded furniture. This type of wood can vary significantly in quality, density, and moisture content, all of which affect its reaction to fire.

Additionally, recycled wood may contain residues of paints, adhesives, or other previous treatments, which can alter its flammability.

The variability of recycled wood presents a challenge for engineers and designers, who must ensure the material meets adequate safety standards. As a result, it becomes essential to adopt specific techniques to increase the fire resistance of this material.

Modern Techniques to Improve Fire Resistance

There are several modern techniques for improving the fire resistance of recycled wood structures. These techniques can be divided into surface treatments, deep treatments, and engineering solutions.

Surface Treatments

Surface treatments are one of the most common techniques for improving the fire resistance of wood.

These include the application of fire-retardant paints, which form a protective barrier when exposed to heat. These paints are designed to expand when heated, creating an insulating layer that protects the underlying wood.

Another approach is the use of gypsum or cement coatings, which can be applied directly to the wood’s surface. These materials are known for their fire-resistant properties and can significantly enhance the fire resistance of structures made from recycled wood.

Deep Treatments

In addition to surface treatments, there are methods for impregnating recycled wood with fire-retardant substances. This process can be achieved by immersing the wood in chemical solutions or injecting these substances under pressure.

Common fire retardants used include phosphate salts, borates, and chlorides, which chemically react with the wood components to reduce flammability.

These treatments are particularly effective for recycled wood with high porosity or irregular density, improving its fire resistance more uniformly.

Engineering Solutions

Engineering solutions involve designing structures that incorporate fire-resistant materials or limit the spread of fire. One example is the use of multilayered panels, where layers of wood are alternated with layers of fire-resistant materials like gypsum or cement.

Additionally, design can include internal fire barriers, compartmentalization, and the use of steel or concrete structural supports, which provide additional protection in the event of a fire. These solutions are particularly useful in buildings that utilize large amounts of recycled wood, where fire safety is a priority.

Regulations and Safety Standards

In many countries, the use of wood in construction is regulated by specific standards that establish minimum fire resistance requirements. These regulations include standardized tests to assess the wood’s performance in the event of a fire, such as combustibility tests, fire resistance, and smoke emission.

For recycled wood, these regulations may be stricter due to the material’s variability. It is crucial that manufacturers and builders strictly follow these guidelines to ensure that the recycled wood used in construction meets all safety requirements.

In recent years, new standards and certifications have been developed for recycled wood, taking into account its specificities and fire-retardant treatments. These certifications provide an additional level of safety for architects and engineers who wish to use recycled wood in their projects.

Major Fires in History

The Great Fire of London (1666)

One of the most catastrophic events in the history of wooden constructions was the Great Fire of London in 1666.

It started in a bakery and quickly spread due to the wooden structures and narrow streets of the city. In just four days, the fire destroyed over 13,000 buildings, including St. Paul’s Cathedral. This disaster highlighted the need for more fire-resistant materials and led to stricter building regulations.

Had modern techniques been available, such as fire-retardant treatments or engineering solutions to compartmentalize structures, the fire could likely have been contained more successfully, limiting the damage.

The Grenfell Tower Fire (2017)

Although the Grenfell Tower fire in London did not directly involve wood, the disaster demonstrated the critical importance of surface coatings. The building’s flammable cladding contributed to the rapid spread of flames, leading to the deaths of 72 people.

If the cladding had been fire-retardant, like those applicable for wood, the fire would have had a much less devastating impact.

The Notre-Dame Cathedral Fire (2019)

The Notre-Dame Cathedral fire in Paris in 2019 destroyed much of the wooden roof structure, dating back to the 12th century. The lack of modern fire-retardant treatments for ancient wood contributed to the rapid spread of the flames.

If the wood had been treated with deep impregnation methods, the damage could have been less extensive.

The Great Chicago Fire (1871)

The Great Chicago Fire of 1871 is another example of disaster caused by unprotected wooden structures.

The fire, fueled by the city’s wooden buildings, destroyed a vast area and caused enormous losses. Modern engineering solutions, such as compartmentalization and fire barriers, could have significantly reduced the spread of the fire.

Conclusion

The use of recycled wood in construction represents a sustainable choice aligned with the principles of the circular economy.

However, to ensure the safety of structures made from recycled wood, it is essential to adopt effective techniques to improve fire resistance.

Modern solutions, ranging from surface and deep treatments to engineering innovations, offer a wide range of options for protecting wood and ensuring the safety of buildings.

As technology and regulations advance, recycled wood can become a safe and resilient construction material, contributing to a more sustainable future without compromising safety.

The ongoing development of techniques and research in this field will be crucial for overcoming current challenges and fully exploiting the potential of recycled wood in modern constructions.