Screeding can be a crucial step in installing underfloor heating systems, but even with careful planning and execution, issues can sometimes arise. Understanding how to troubleshoot common screed problems can help you maintain the efficiency and longevity of your heating system. Here are some typical issues and how to address them.
For the best results, ensure the use of an accredited screed installer.
Cracking in the Screed
One of the most common issues with screeding is cracking. This can occur for several reasons, including improper curing, thermal expansion or insufficient reinforcement.
Solution:
To prevent cracking, ensure that the UFH is commissioned properly to the screed manufacturers guidelines; if not cracking and debonding of the floor covering are possible. UFH commissioning gradually heats the underfloor system up to allow the screed to adjust to temperature changes and helps dry the screed out.
Uneven Screed Thickness
An uneven screed thickness can affect the efficiency of your underfloor heating system and the quality of your floor finish.
Solution:
To achieve a smooth, level surface, ensure the subfloor is properly prepared before applying the screed. For flowing screeds, their self-levelling properties typically provide a smooth finish, but it’s essential to follow the manufacturer’s guidelines for the best results. If screed thicknesses are greatly different then alter the insulation thickness as allowed to even out the screed thickness.
Slow Drying Times
Excessive drying times can delay your project and lead to further complications, such as mould growth or floor covering damage.
Solution:
Choose the appropriate type of screed for your project timeline. Fast drying flowing screeds can significantly reduce drying times compared to traditional sand and cement screeds. Ensure adequate ventilation and maintain an optimal temperature to facilitate the drying process. If necessary, use dehumidifiers to help speed up drying in high humidity conditions.
Inconsistent Heating
Inconsistent heating across the floor surface can result from poor application or issues with the underfloor heating system itself.
Solution:
Before laying the screed, ensure the underfloor heating pipes are spaced correctly to the design and are fixed securely to the floor. During the screed application, ensure the heating pipes are pressurised for correct installation.
Moisture Retention
Retained moisture in the screed can cause mould growth, affect the efficiency of the heating system and damage floorcoverings.
Solution:
Conduct thorough moisture tests before applying the final floor covering. Using an approved method, check that the screed has dried to the recommended moisture content level. The base is deemed to be sufficiently dry to receive most floorcoverings when the equilibrium relative humidity (ERH), as measured by a surface mounted flooring hygrometer box or similar, is 75% RH or less. Allow sufficient drying time and ensure proper ventilation to prevent moisture retention from within the screed
Delamination of the Floorcovering
Delamination occurs when the floorcovering separates from the screed.
Solution:
Ensure the screed surface is clean, dry, and free of contaminants before applying the floorcovering. Follow the manufacturer’s guidelines for applying the primers and smoothing compounds if required to ensure the proper bond. Again gradually heat the system to help the smoothing compound to acclimatise without separating.
