Liquid screed has become a popular choice in modern construction due to its ease of application, fast curing times, and high performance. This comprehensive guide will provide you with everything you need to know about liquid screed, including its benefits, types, application processes, and maintenance.
What is Liquid Screed?
Definition and Composition
Liquid screed, also known as flowing screed, is a type of floor screed that is designed to be self-levelling and easy to apply. It is a mixture of cement, sand, and additives that enhance its flowability. The mixture is pumped onto the floor, where it flows and levels itself, creating a smooth, even surface.
Key Characteristics
- Self-Levelling: Liquid screed spreads and levels itself without the need for manual smoothing.
- High Fluidity: Its fluid nature allows it to fill gaps and cover large areas quickly.
- Fast-Drying: Special additives in the mix can accelerate the drying time, reducing project delays.
Types of Liquid Screed
Anhydrite Screed
Composition and Properties
Anhydrite screed, also known as calcium sulfate screed, is made from anhydrite (a form of calcium sulfate) instead of traditional cement. It is known for its excellent flow properties and is often used in conjunction with underfloor heating systems.
Advantages
- Quick Drying: Dries faster than traditional cement-based screeds.
- Smooth Finish: Provides an exceptionally smooth surface for floor finishes.
- Thermal Efficiency: Works well with underfloor heating systems due to its thermal conductivity.
Disadvantages
- Moisture Sensitivity: Requires a dry substrate and is sensitive to high moisture levels during application.
- Substrate Preparation: Needs careful preparation to ensure proper adhesion and performance.
Cement-Based Liquid Screed
Composition and Properties
Cement-based liquid screed is made from a mixture of cement, sand, and additives. It combines the fluidity of liquid screed with the strength and durability of traditional cement.
Advantages
- Versatility: Suitable for a wide range of applications, including residential and commercial projects.
- Strength: Provides a strong and durable base for various flooring materials.
- Moisture Tolerance: More tolerant of moisture than anhydrite screeds.
Disadvantages
- Longer Drying Time: Typically takes longer to dry compared to anhydrite screeds.
- Less Smooth Finish: May require additional finishing work to achieve a perfectly smooth surface.
Fast-Drying Liquid Screed
Composition and Properties
Fast-drying liquid screed contains special additives that accelerate the curing process. This type of screed is ideal for projects with tight deadlines where quick turnaround times are essential.
Advantages
- Quick Turnaround: Significantly reduces the time needed before floor finishes can be applied.
- Efficient: Minimises downtime and speeds up the overall construction process.
Disadvantages
- Higher Cost: Typically more expensive due to the specialised additives.
- Requires Expertise: Application must be managed carefully to ensure proper curing.
Benefits of Liquid Screed
Smooth and Even Surface
Liquid screed provides a perfectly smooth and level surface, essential for the final flooring layer. Its self-levelling properties eliminate the need for extensive manual finishing, resulting in a flawless finish.
Quick and Efficient Application
The fluid nature of liquid screed allows for rapid application over large areas. It flows easily into place, reducing the time required for installation compared to traditional screeds.
Enhanced Thermal Conductivity
Liquid screed, particularly anhydrite screed, has excellent thermal conductivity, making it highly suitable for use with underfloor heating systems. It effectively transfers heat, improving the efficiency of the heating system.
Reduced Labour Costs
Due to its self-levelling properties and ease of application, liquid screed requires less manual labour, potentially lowering overall installation costs. The need for fewer skilled workers during the screeding process can also contribute to cost savings.
Versatility in Use
Liquid screed can be used in a variety of applications, including residential, commercial, and industrial projects. Its adaptability makes it a popular choice for different types of flooring installations.
Application Process
Preparation
Site Inspection
Before applying liquid screed, conduct a thorough site inspection to assess the substrate’s condition. Ensure that it is clean, dry, and free from any contaminants that could affect the screed’s adhesion.
Substrate Preparation
Prepare the substrate by removing any loose material, debris, or old floor coverings. In some cases, it may be necessary to apply a primer or bonding agent to ensure proper adhesion of the screed.
Mixing and Pumping
Mixing
Liquid screed is typically mixed in large quantities using a ready-mixed screed delivery system. Ensure that the mixture is well-combined and free of lumps before application. Follow the manufacturer’s guidelines for mixing ratios and procedures.
Pumping
Use a screed pump to deliver the liquid screed to the application area. The pump ensures an even and consistent flow of screed, reducing the risk of uneven coverage. Pour the screed in a continuous manner to avoid joints or seams.
Levelling and Finishing
Levelling
Once the liquid screed has been poured, use a long-handled tool or a laser-guided screeding machine to level the surface. Ensure that the screed is evenly distributed and that any high or low spots are corrected.
Finishing
Allow the liquid screed to cure according to the manufacturer’s recommendations. Avoid foot traffic and heavy loads until the screed has fully cured. Perform any necessary finishing work, such as smoothing or polishing, as required.
Maintenance and Care
Curing and Drying
Proper curing is essential to achieve the desired strength and performance of the liquid screed. Follow the manufacturer’s instructions for curing times and conditions. Ensure that the screed is kept at the recommended temperature and humidity levels during the curing process.
Avoiding Common Issues
Cracking
To minimise the risk of cracking, ensure that the substrate is properly prepared and that the screed is applied evenly. Avoid overworking the screed during application and adhere to recommended drying times.
Moisture Problems
Address any moisture issues in the substrate before application. Monitor the screed for signs of excessive moisture or dampness and take corrective measures if needed.
Long-Term Maintenance
Regularly inspect the screed for any signs of wear or damage. Perform routine cleaning and maintenance to keep the surface in good condition. Address any issues promptly to prevent further damage and extend the lifespan of the screed.
Conclusion
Liquid screed offers numerous benefits, including a smooth finish, quick application, and compatibility with underfloor heating systems. By understanding the different types of liquid screed, their advantages and disadvantages, and the application process, you can make an informed decision for your construction project. Proper preparation, application, and maintenance will ensure that your liquid screed performs optimally and provides a durable foundation for your flooring needs.
