Screeds in Flooring Systems – Innovations, Controls, and Challenges
The screed is a cornerstone of the flooring system, serving as both a structural and functional support for final coverings such as ceramics, wood, or resins. Despite its critical role, it often remains “invisible” once covered by the finished floor.We believe it is essential to recognize the importance of screeds, understand the innovations currently applicable, and master the control methods to be performed before laying the covering, with particular focus on the new UNI 11944 standard and the code of good practice developed by the national association dedicated to screeds and industrial flooring.
The Role of the Screed: an underestimated element
The screed can be likened to the “chassis” of the flooring system, ensuring mechanical strength, flatness, and compatibility with coverings. However, its significance is often overlooked, leading to issues such as “curling” – the deformation of the screed due to uneven curing – which can compromise the quality of the finished floor. This underestimation is compounded by a shortage of skilled labor and the mistaken belief that “screed errors can be corrected with a bit of adhesive” during the laying process. Promoting professional qualifications and standardization is vital to raising quality standards in screed construction and engaging younger generations in a trade that addresses fundamental human needs, such as building homes.
The UNI 11944 Standard: A Milestone for Screeds The UNI 11944 standard marks a significant step forward as the first regulation specifically dedicated to screeds. Developed through collaboration between regulatory bodies and industry associations, this standard overcomes the limitations of previous regulations on coverings, which only provided generic guidance on screeds. The UNI 11944 defines requirements and control methods to ensure screed quality, from design to installation, building on a code of good practice that outlines guidelines for checks during mixing, pouring, and final verification. The harmonized UNI EN 13813 standard and the Construction Products Regulation (EU 305/2011) establish the requirements for CE marking, which is not merely a quality label but a certification of the product’s performance. The UNI 11944 standard integrates these requirements, introducing standardized methods for on-site sampling and verification of mechanical properties, such as compressive and flexural strength.
Control Methods: Standardization and Practice
The code of good practice and the UNI 11944 standard categorize controls into two types:
Execution controls: These include checks for flatness (using a 2-meter straightedge with calibrated spacers), compactness, surface roughness, and the absence of cracks.
Pre-laying performance controls: These encompass tests such as scratching, pull-off (direct tensile strength), impact test (dynamic load resistance), sclerometer (surface strength estimation), and residual moisture measurement using a carbide hygrometer.
As discussed in the following sections, these tests aim to ensure the screed meets the specific requirements of the intended covering. For wooden floors, for instance, controlling residual moisture is critical to prevent moisture transfer from the subfloor to the screed, which could damage the covering. For ceramics, flatness and compactness are essential to avoid issues like detachment between the floor and baseboard.
Innovations and Challenges: Conscious and Integrated Design
In recent years, screeds have taken on increasingly complex roles, meeting acoustic, thermal, and mechanical requirements. The UNI 11944 standard, in paragraph 4.7, emphasizes the importance of defining the type of flooring during the design phase to determine the required screed performance. However, designing the flooring system demands an integrated approach involving designers, applicators, and manufacturers to overcome the fragmentation among different project phases. Another challenge is the standardization of on-site testing. A research project is underway to refine methods for verifying parallel (UNI 10827) and perpendicular (UNI 13892-8) stresses, reducing variables that affect result reliability. The goal is to develop faster, more cost-effective, and uniform protocols, ensuring absolute reference values for acceptance testing, which are crucial for approving the work.
It’s Not Just a Matter of Cost
Raising awareness among professionals is critical to addressing industry challenges. Associations organize training events, often with recognized professional credits, to highlight the importance of considering the entire flooring system, from subfloor to covering. The tendency to opt for low-cost materials and neglect preliminary design of the final covering poses significant risks, such as curling or tile detachment. Debunking misconceptions, such as the notion that a sand-cement screed is always sufficient, is essential to fostering a culture of quality. The evolution of screed materials, with optimized granulometric aggregates and additives that enhance mechanical performance, is another key factor. However, screed quality also depends on site conditions, such as the absence of drafts or exposure to sunlight, which can cause uneven dehydration.
Knowing the Standard is Not Enough
The UNI 11944 standard and the code of good practice are essential tools for raising screed quality standards, ensuring mechanical performance, durability, and compatibility with coverings. However, the construction industry faces cultural and organizational challenges, from a shortage of skilled labor to the need for integrated design. Collaboration among screed applicators, installers, manufacturers, and designers, coupled with ongoing training and outreach efforts, will be crucial to transforming the screed from an “invisible” element into a recognized cornerstone of the flooring system. Aiming for quality does not necessarily mean producing expensive solutions but rather finding a balance between performance, cost, and intended use to meet market demands without compromising the durability of the work.
![durezza massetto piastrelle Vicenza](data:image/webp;base64,UklGRlYAAABXRUJQVlA4IEoAAADwAQCdASoPAAYAAUAmJZwC7AEWOaiwEIAA/vm7MGan7QOORO0PQrkat7Fcfb5aaTf97vyxdhZXt9L6gm6eEE2HS5gqWxhoWwAAAA== "Qui sto facendo la verifica graffiando con un chiodo il massetto. Quando il massetto "sfarina" e si sgretola non è idoneo alla posa")
![durezza massetto piastrelle Vicenza](/sites/default/files/inline-images/massetto-piastrelle-Vicenza.jpg "Qui sto facendo la verifica graffiando con un chiodo il massetto. Quando il massetto "sfarina" e si sgretola non è idoneo alla posa")
