What Thickness Should Screed Over Underfloor Heating Be?

How Thick Should Liquid Screed Over UFH Be?

When installing an underfloor heating system, it is highly important to ensure that the right type and thickness of screed is applied on top to get the most efficient results from your system. Using the wrong type of screed could land you in trouble and your efforts of obtaining a good heating system could all go down the drain.

Underfloor-HeatingEvery flooring project is different, and therefore it is essential to understand your building, its uses, and use the screed which is most suitable for it. For example, you are likely to receive the optimum solution with a solid floor when you have installed underfloor heating systems along with pipes concealed in screed and on top of the floor insulation. You can also receive heat upto 100 W/min timber suspended floors.

On the other hand, concrete floors take slightly more time to heat up but they retain the heat for a longer duration. One of the main advantages of underfloor heating combined with screed floors is that they do not require as high water temperatures as timber suspended floors need, meaning that your heating bills will be significantly lowered.  Approximately 45o C water into the screed floor should be sufficient.  Some people suggest using lower temperature heat sources like heat pumps as the main source for underfloor heating.

Various techniques are used to install underfloor heating systems and based on the floor, the insulation process is determined. Sometimes, vapour barriers are fitted where necessary. Some companies recommend a specific thickness for insulation, however you should ensure that they follow the proper building regulations. Insulation restricts excess heat loss and distributes heat uniformly at the required places, making for a more efficient heating process.

It is highly important to ensure that the correct thickness of the screed is maintained, because even a minor change in them could ruin the entire floor and you could face significant consequences. If you are using a traditional screed mixture which includes sand and cement, the minimum thickness should be of 65mm. Generally, an approximate thickness between 65mm to 75mm is successfully used for this screed. However, there are exceptional cases wherein the screed may be laid successfully at about 100mm in thickness.

If you are using a stronger screed or add fibre to the screed, then the minimum thickness can fall down to 50mm. For instance, if you utilise anhydrite screed for your floor, a minimum of 50mm thickness is applicable. However, it is always better to confirm the measurements with an experienced screed supplier to make sure the job is carried out correctly.

Floor installations are suggested for upper levels like block floors. Most insulation boards are of 30mm thickness, but you can make use of shorter clips for clipping the pipe to its position. Screed thickness preferably remains the same as for the ground floors.

Several underfloor heating systems in concrete depend on the thermal conductivity of the screed in order to distribute the heat to the rooms. Some systems have slow responses and therefore it is advisable to install systems that have setback options so that it is convenient to use throughout the day. If you wish to have additional comfort for the system, you can make use of programmable room thermostats.