Underfloor Heating Screeding

Traditional Screed

Traditional sand and cement screed is mixed in the ratio of 1:3-4.5 with water and polypropylene fibres which reduces surface micro-cracking within the screed and generally applied to a depth of 75mm.  The screed is mixed semi dry to an earthy consistency and the snowball test is the simplest and most effective way of judging the correct quantity of water.  The snowball test consists of creating a snowball like ball of screed and if it holds together without evidence of excess water this is deemed to be of the correct proportion.  If the snowball does not hold together then more water should be added to the mix.

Traditional cement sand screeds are suitable for all manner of construction methods ranging from bonded, unbonded, floating and heated floors.

CSC Screeding Underfloor Heating Screeding
CSC Screeding Fast Drying Screeds In A Hallway

Fast Drying Screeds

Fast drying screeds: These are enhanced screeds with accelerated drying times, and are generally recommended as the ideal screed systems for underfloor heating. These screeds yield the best results when applied using forced action mixers such as screed pumps or pan mixers. These types of screeds have additives mixed along with the cement sand mixture to improve their drying time.

Fast drying accelerated screeds are now very much in preference because of the quick drying time they offer. Many fast drying floor screeds allow foot traffic to proceed as early as 12 hours and facilitate the early installation of the final floor finish, allowing the heating system to be used much earlier. Proprietary screeds are highly recommended fast drying screed systems that perform well when used over underfloor heating.

Free Flowing Screeds

These screeds have the advantage of being easy to install as the liquid can be poured quickly to cover a larger area. However the drawback is that they cannot be used in wet areas and have long drying times. Some flowing screeds cannot be used in wet areas and cannot be laid to falls.

Free flowing screeds are gypsum based liquid screeds that can be applied at reduced depths compared to the traditional screeds. Ideal for screeding over large areas. But the major drawbacks are, these screeds are not suitable for wet areas and are generally not compatible with cementitious adhesives. The surface usually requires sanding and priming, before a bonded finish can be applied.  Proprietary screeds are highly recommended fast drying screed systems that perform well when used over underfloor heating, some of the commonly recommended free flowing screeds are Tarmac, Breedon, Cemfloor, Longflow.


Under Floor Heating

The heating elements for the underfloor heating are usually encased in a layer of screed before the installation of the final floor covering. In the case of hydronic underfloor heating, the heating pipes are usually secured to insulation panels on the floor slab fitted with moisture barriers, and the screed layer is laid over this to provide a level surface for installing the final floor finish.

Though traditional sand, cement screeds are generally used for screeding over underfloor heating, this can be quite time consuming as the screeds require a long time period for drying sufficiently to take on the final floor covering. However, though an obvious option, the underfloor heating system cannot be utilised to accelerate the drying process as it can result in the cracking of screed due to quick drying.

A graphic explaining underfloor heating screeding

Fast Drying Floor screeds help to overcome this issue, drying much faster than traditional screeds while allowing the screed mix to hydrate fully. They act as capillary pumps, removing excess water and locking in the rest of the water by crystallisation, thus preventing the cracking of screed. An example for Fast Drying screed is Isocrete K-Screed fast drying floor screeds. The different types of screed laid over underfloor heating are:

Underfloor heating(UFH) is a highly efficient form of space heating that generates heat through electric or hydronic heating elements embedded beneath the surface of the floor. The heating elements are typically secured to insulation panels on the floor slab and the screed layer is installed over the heating elements before laying the final floor finish.

Apart from serving as a level surface for taking on the final floor finish, a good screed plays the important role of conducting the heat evenly across the surface of the floor, without producing any hot or cold spots. A good quality screed, laid to the right depth helps to retain the heat for longer hours, reducing the energy required at the source and improving the energy efficiency of the UFH system. A wide range of screeding options are now available for underfloor heating systems:


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What We Have Done

Our Work


High Wycombe

Centre Square, Lily’s

CSC Screeding secured the insulation and floor screeding package at the landmark High Wycombe development called Centre Square at Lily’s Walk for Inland Homes Plc.



Prince of Wales Drive

CSC Screeding were engaged by Berkeley Group to carry out Calcium Carbide testing, on anhydrite screed with underfloor heating, throughout their development at Prince of Wales Drive.

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CSC Screeding are members of Constructionline, CHAS and Builders Profile where a predefined Health & Safety questionnaire is pre-completed and our clients have direct access to the information. Documents contained in the pre-qualification system are updated throughout the year, ensuring continued compliance. We have focused on developing the business through constant innovation, implementation and collaboration.

We were an early adopter of FORS – gaining Bronze accreditation – as we recognised this would become more widely requested on construction sites.

We are now ready for the business to grow with the increasing demand.