The power of screeds with floor cleanups and underfloor heating

The history of underfloor heating dates back to the Neoglacial and Neolithic periods. Today, the modern-day underfloor heating systems use either electrical resistance elements or fluid flowing in pipes. Essentially, the Underfloor Heating (UFH) system gets embedded within the screed, and any issues with either affect both.

Yet another reason for the popularity of underfloor heating is the drive towards ‘greener’ building systems. This is now applied in varied sectors, including education, leisure and residential.

What are the causes of underfloor heating failure?

Typically, these are attributable to any of the following:

• Lack of address to the floor layout at an early stage
• Failure to address the floor finish early
• Incorrect installation of the UFH system or screed
• Inappropriate screed mixture
• Excessive moisture in the screed

Types of Screeds

At the outset, screeds come in varied categories. The most common variants are:

• Bonded Screed. The screed layer is fully stuck to the substrate using a primer or bonding agent. This method is ideal for thinner screeds that involve heavy leading. It is also best to use when there is insufficient space available to lay an unbonded screed. Now, bonded screed can be sand or cement, and the optimum thickness ranges between 25-40 mm.
• Unbonded Screed. These screeds get applied over a damp-proof membrane (DPM). This screed gets laid on top of the concrete base. Note that the minimum thickness of unbonded sand and cement screeds are usually around 50 mm. However, there are exceptions! Calcium sulphate unbonded screeds require a minimum depth of 30 mm. The flooring does not come in direct contact with the structure. Hence, the potential impacts of settlement or shrinkage are deemed less problematic. Here, the DPM forges a barrier that prevents the damp from rising from the substrate. Another aspect is it is prone to curling if dried quickly. However, calcium sulphate screeds are not susceptible to curling.
• Floating Screed. This one gets laid on top of the insulation. The objective is to create a thermally-efficient floor. This type of screed gets used where the UFH systems are provided or acoustic insulation is required. Here, the sand and cement screeds have a thickness greater than 65mm for lightly-loaded floors and 75mm for heavy-loaded ones. Once again, calcium sulphate screeds are the exception! These can get installed at 35mm for domestic use or 40mm for commercial applications.
• Flow/Liquid Screeds. This is poised to become the industry standard in floor screeds. The floor type is also known as self-compacting screed or calcium sulphate screed. This flow screed is best for light-foot traffic in 24-48 hours. Plus, partitions can get installed, or the screed can get loaded out a week post-installation. Note that most screeds get applied as floating screeds. This method is the most practical for placing on top of underfloor heating and insulation solutions.

General application guidelines

Several pointers are integral when ensuring that a floor screed gets successfully applied over the underfloor heating. These are:

• Before the installation process, ensure the area is smooth and flat. A flat and smooth surface helps ensure the installation sits level. Also, the correct screed zone/floor buildup is made available before installing the underfloor heating and screed package.
• The correct screed must be specified; to the right thickness. One should also consider heat output, point loading, size and scale of the floor area and the floor finish. The design of the UFH depends on the screed type and the need for thermal movement, which causes expansion.
• Make sure to install expansion and perimeter strips as per the project specification. Also, the screed must be mixed and applied according to the manufacturer’s instructions.
• When it comes to the placement of movement or expansion joints, typically thought out during the design stage, one must carefully consider the screed and underfloor heating. Doing so is deemed integral for mitigating the cracking in the screed.

Preventing your floor from screed issues

Applying screed to the floor requires that you meet the below conditions. There are specifics that need to be taken care of as well. But, at the outset, the basics are next.

• First, the substrates must be level. There must be no pockets or high spots. This renders even thickness to the screed.
• Also, the insulation must be tightly-butted together and level.
• Keep pedestrians at bay during the drying period
• Abort constructing screed during cold weathers of less than 5°C
• Movement joints shall be required if Bay sizes exceed 40m2
• Adhere to specific drying times. Much depends on the type of screed used.

Additional Considerations

Another crucial aspect is understanding the impact of underfloor heating on screeds. And, even more so, how those screeds react to the heating output. Design parties with a vested interest in the heated subfloor zone approach the task with unique perspectives and knowledge. Also, UFH gets consideration because of the mechanical and electrical (M&E) plan. The objective is comfort for the building user. The screed helps accommodate floor finishes and the loadings of a building. Also, it is not uncommon for experts to look at cracks seen as a fault of the screed. Mostly cracks are a symptom of subfloor zone problems. In this stead, repairing a crack is not the immediate answer. The more pressing issue is to find the cause and then repair it.

At the end of the day
Remember that size and shape of the rooms and corridors shall determine the design and installation of the UFH and screed systems. One must look for any movement joints designed in the screed. Yet another aspect is flexible insulation. Also, corridors and door thresholds require individual joints after laying the screed. If you are dazed or doubtful about underfloor heating and floor cleanup, Screed Easy provides a team of specialists that possess the requisite tools and experience for getting the job done.