Asbestos in rooftops: Prudencio’s approach and practices in its encapsulation system

In 2008, asbestos cement roofs covered about 6 billion square meters in Portugal. Renovating all potentially asbestos-containing buildings proves unviable and expensive.

Asbestos cement, among asbestos products, poses minimal risk as the fibers are tightly bound by cement, reducing the likelihood of release.

Risks escalate when fiber cement undergoes direct handling, such as during removal, heightening the likelihood of particle release. Additionally, removal exacerbates the long-term environmental impact of landfills and their burdened capacity.

For these reasons and because of the unique efficiency of Prudencio encapsulation, both in terms of worker protection, thermal insulation and the waterproofing system, we are, in most cases, strong advocates of this solution.

Continue reading to discover the safe practices adopted and the description of our method.

The state of the art

We found that the options available for dealing with the asbestos cement problem were very poor and limited to two technically weak solutions that posed risks to the environment and health: removing the asbestos cement to replace it with sandwich panel systems or painting the asbestos cement sheets with specific paints.

This last one shouldn’t even be called encapsulation, as it doesn’t protect the fiber cement from physical or mechanical aggression, doesn’t include thermal insulation and doesn’t guarantee waterproofing. Moreover, it involves washing or scraping the asbestos cement beforehand in order to ensure that the paint adheres correctly, a procedure that carries a high risk of releasing fibers.

The sandwich panel solution brings with it the weaknesses of sheet metal systems, such as discontinuity in gutters, ridges and others that cause water to enter on windy days and high rainfall rates or in the event of blockages, fragile and ineffective finishes to the various elements on the roof, such as walls, ridges, chimneys, skylights and stairwells, using silicon seals and apparent fixings, as well as corrosion that often appears earlier than expected, both in the roof sheets and in the finishes, cuts and fixings.

The motivation: protecting the environment, the health of our workers and the general population

To avoid health risks and ensure a safe encapsulation, we have carefully considered 3 pillars of our solution:

1. Risk assessment

We have implemented a consensual and effective risk assessment, based on an analysis of all the legal and regulatory documents, which include the various decree-laws, in particular no. 266/2007, of July 24, which regulates the protection of workers against the risk of exposure to asbestos during work, and the Good Practice Guide for preventing or minimizing risks in work that may involve asbestos, drawn up by the Committee of Senior Labour Inspectors (CARIT).

It was also essential to obtain the opinion of the ACT of São João da Madeira, the most qualified and experienced in matters related to asbestos, and to use the services and knowledge of INSA – Instituto Nacional de Saúde Dr. Ricardo Jorge – which establishes the rules for taking and delivering samples of asbestos cement to ascertain the presence or absence of asbestos in this material and carries out the test to assess occupational exposure to respirable fibers.
Our long experience in rehabilitating asbestos cement roofs helps us to obtain competent assessments.

2. Practices to protect workers

In the application of our encapsulation solution, we use appropriate work processes and the methods available to reduce workers’ exposure to fiber cement to a minimum:

a) We have reduced the number of workers to the minimum possible during the stages of the work when the fiber cement is not yet completely covered, i.e. during the application of the reinforcing and fixing metal structure and the PIR thermal insulation boards;

b) The work phases mentioned in the previous section have been developed in such a way as to be simple and quick to apply, an example of which is the use of large PIR boards in this system – 2.5m x 1.2m – which guarantees great speed of application;

c) We use application techniques that avoid handling the asbestos cement. When it is strictly necessary, as in the case of taking samples to be analyzed by INSA for the existence or not of asbestos in the fiber cement, we never use cutting tools (especially grinders) and we use the wet route to carry out this procedure;

d) Our workers receive training on safe practices in this type of work and the dangers associated with asbestos, which is periodically revalidated;

e) We advise our clients to keep information on the existence of asbestos cement on the roof and the encapsulation solution applied in their records, providing them with full information on the methods and materials used.

3. Lightweight metal structure for fixing and reinforcing the roof

This is an essential component of the encapsulation system, as it guarantees the safety of workers against falls from a height and the fixing of the entire system without drilling into or manipulating the fiber cement. It also provides structural reinforcement for the roof, ensuring that future use of the roof for maintenance work is carried out in a completely safe and comfortable manner.

The goal: total efficiency

Prudencio’s encapsulation not only solves the problem of fiber cement, keeping it sealed and innocuous, but also eliminates the weaknesses described in the solutions traditionally proposed on the market, offering additional benefits such as preserving the existing structure, speed and comfort in processes, and less environmental impact.

What was a potentially dangerous rooftop is now a sustainable and safe system. Here’s how we did it:

Waterproofing membrane

We applied Köster’s top-quality TPO waterproofing membranes to ensure a reliable, long-lasting and environmentally friendly end result. This improvement also gives the roof a more attractive appearance.

Thermal insulation boards

In addition to improving the building’s energy efficiency, these panels serve as a solid base for the waterproofing system and prevent the tensions in the substrate from being transmitted to it. As with waterproofing, we apply the thermal insulation completely continuously, eliminating thermal bridges and the inherent condensation problems.

Metal reinforcement for fixing and reinforcement

This lightweight metal mesh guarantees safety during the application of the solution, fixing the system without drilling or manipulating the fiber cement and structurally reinforcing the roof.

Preserving corrugated fiber cement roofing

The fiber cement roof does not need to be removed. Instead, by being encapsulated, the fiber cement becomes the basis of the new thermal insulation and waterproofing system.

This approach completely confines and protects the fiber cement from the causes that lead to its degradation, providing mechanical, thermal, and moisture protection.