Aug. 04, 2025
Too high or too low room temperature, leaks, cracked tiles - these are only a few possible effects of various types of mistakes made while planning or installing the underfloor heating system. Malfunctioning floor heating is usually the result of careless installation or adopting improper solutions. Today we will look at 10 common mistakes made when installing the underfloor heating system.
The lack of a proper design while installing any heating system may have disastrous effects. In the case of underfloor heating, the layout as well as the shaping of the heating pipes must be adjusted to the parameters of the supply water in the heating system, the screed thickness, the type of floor covering and heat demand. Lack of reliable documentation does not only lead to higher costs of maintenance, but it also spells trouble in case of heating system failure. It is important to document the actual layout of the heating pipes on the room plan, especially in the area between the rooms, under the windows and near the walls. If we know the actual dimensions of the loops, we can avoid damaging them accidentally while installing threshold strips or other elements that require drilling in the floor.
Underfloor heating system must be installed in correct order. It should start after other systems have been laid, otherwise the heating pipes and other elements of the heating system may be damaged. Manifold cabinets and manifolds should be installed before laying the pipes. The floor heating distributor box should be installed as close to the underfloor heating system as possible, rather than in a remote boiler room. It is worth remembering that it is impossible to install the whole underfloor heating system when the house is at the open shell stage without the windows and doors. These elements are necessary to prevent draughts when the screed is setting. Thanks to this, we may prevent excessive drying of the screed surface.
Some problems may also result from poorly executed construction works. Before installing the underfloor heating system, the floor must be prepared properly. What are the most common mistakes which bring about unpleasant consequences? The three most serious ones concerning the the floor preparation are listed below.
Further layers of underfloor heating system such as thermal insulation, heating pipes and concrete screed cannot be laid on uneven surfaces. Careless preparation of the base, skipping the levelling and cleaning stage means that the thermal insulation boards will not adhere well and will not provide a stable support for the screed, which may lead to cracking. In places where the screed cracks, there is a risk that the heating pipes will be damaged. Furthermore, uneven ground requires different thickness of the screed on the floor. That is why it is so important to level the surface before laying the insulation.
Heating pipes form the so-called heating circuit, the length of which should not exceed 100 m depending on the diameter of the pipes used. Therefore, during installation work, make sure that the installer does not make longer heating loops. It is also worth remembering that each loop should be made up of one continuous length of pipe. Connections are allowed in the event of pump damage and with the use of special repair couplings which can be covered with concrete. To avoid problems, it is therefore necessary to select the pipes in such a way as to avoid connections in the places which will be covered with the screed. Such connections are the most vulnerable points because dirt easily deposits there, which results in defects. Failure to follow the instructions will increase the hydraulic resistance, resulting in insufficient heating of certain areas of the floor.
The heating pipes which will carry water must be firmly attached to the ground. First, a special pipe-positioning foil with anchor mesh should be placed on the polystyrene layer. Next, the pipes are secured to the foil using the clips included in the underfloor heating system set. If the pipes are not fastened properly, they can disconnect from the ground while the screed is poured on the ground. In addition, if the system includes copper components, pipes should not be laid directly on concrete as they may corrode. Copper pipes must be protected with an additional layer of plastic. An alternative is to use pipes made of different materials such as plastic or multi-layer pipes. It is worth choosing high-quality products that exclude the risk of damage.
The floor in which the heating pipes are embedded requires proper expansion joints. The heating surface expands due to the heat from the pipes, which is why it is necessary to make expansion joints. If the room is large or has an unusual shape, it is necessary to plan additional expansion joints in the screed. The lack of such gaps or making them only in the floor covering rather than through the screed can lead to scratches and cracks. It is important to arrange the heating pipes in such a way that the expansion joints do not cross them.
One of the last stages of installing the underfloor heating system is to bury the heating pipes in screed. At this stage, it is recommended to supervise the work of people who pour the concrete to avoid damage to the heating pipes or covering the gaps or expansion joints. It is possible to lay the floor covering only after the screed has dried properly and reached its optimum parameters. In order for the concrete to set well, the surface must be prevented from drying excessively. After about 21 days you need to preheat the screed so that the remaining moisture is removed.
Unfortunately, not every material is suitable for covering the floor if we decided to install the underfloor heating system. Therefore, the question of what material will be the best is one of the key questions when it comes to the installation of hydronic underfloor heating. The type of floor covering determines the heating efficiency. For example, a change from ceramic tiles to floor panels will decrease the heating efficiency two times, which in turn will lead to problems with maintaining the pre-set temperature when the outdoor temperature is low. A common solution in this case is to increase the supply temperature, which is not a good solution because it can damage the heating system as well as the floor covering itself. The types of materials used while installing the underfloor heating system are shown in the graphic below.
Before laying the screed, the system must be filled with water in order to check if the pressure in the system has not dropped excessively after a few hours or even a day. At this stage, it is easier to detect and remove leaks than after the pipes have been covered with concrete. The pressure test should be carried out when all heating circuits are filled with water. Sometimes installers give up this activity altogether or fill the pipes with air instead of water. Conducting the pressure test improperly may have serious consequences. It is essential to make sure that there are no leaks before we lay the screed. In the event of an undetected leak, the system can be seriously damaged and repair will be difficult and expensive.
When installing the underfloor heating system, it is a mistake to limit yourself to the simplest solutions and decide not to use controllers for managing the underfloor heating. Neglecting the underfloor heating control leads to significant energy loss, which results from high thermal inertia of the system. Our modern underfloor heating controllers from the 5, 7 or 8 series will allow you to enjoy the advantages of installing this type of heating in your home as well as reasonably manage your home budget.
Read also: Balancing your underfloor heating system as a way to achieve greater thermal comfort and lower heating bills.
Installing underfloor heating is a perfect solution for those who love comfort and convenience. It is worth remembering, however, that only a well-designed and well-made system will ensure the expected results. Mistakes made while laying the underfloor heating system affect the failure rate and reliability of the entire system. By choosing proven solutions, competent contractors and reliable manufacturers, you will be able to enjoy a warm floor for many years.
Grundfos UPM3 – The next generation of Underfloor Heating Pumps
Here at Underfloor Heating Systems Limited we also make sure we use the latest new technology.
We have now updated our pump to the Grundfos UPM3 pump.
This pump comes with a number of benefits;
– 7 m Head
– Easy access to the user interface from the front
– Plug in wire
– Easy access to de-blocking screw from the front
– Intelligent configuration
– Very high efficiency pump
– Ultimate reliability – Ceramic bearing shaft, double de-blocking system and high temperature resilience
– Easy for the end user to adjust the settings.
The UPM3 pump exceeds efficiency benchmarks.
The pump has been lab and field tested all over the world and it has passed with flying colours.
As a guideline the cost for supply is £ 12 – £ 14 per sqm depending on the floor area for wet underfloor heating. An install service is available as an option and that can be between £ 5 – £ 6 per sqm.
Note, that very small area’s will be more expensive than above.
Many customers ask us if it is cheaper than radiators?
The answer is that it is probably 10 % -20 % more expensive to purchase, but the running cost is lower for water underfloor heating.
Another common question is if water underfloor heating is cheaper than electric underfloor heating?
The answer is simple, electric underfloor heating is cheaper to buy, but the running cost is much higher than any wet underfloor heating system.
Electric underfloor heating is mainly fitted in small wet rooms, such as WC/En-Suites and Bathrooms.
Our wet underfloor heating system is made of parts from all over Europe/UK.
We only use high quality products such as the multilayer pipe from Valsir, Reliance Water Controls mixer pack, Heatmiser controls, etc.
It is our own heating system, using what we think are the best possbile products available.
Online customers will know the brand Nordic Pro and Nordic Pro 2 systems which we supply.
We supply and install new systems, but we do not service or repair other companies systems, neither do we supply electric underfloor heating.
The best solution is always a screeded floor.
We would recommend below system;
Use 6 mm Superfoil below the mesh, tie the underfloor heating pipes to the mesh with cables ties.
Finally use 50 mm fibre screed or 50 mm liquid/anhydrite screed on top of the mesh/pipes.
There are a number of board solutions for underfloor heating for existing floors, ie Profoil, Profix, etc, but a screeded floor will always perform the best and give the end user the most effiecient wet underfloor heating system.
We sell the smaller water underfloor heating systems online on our ecommerce shop;
https://www.underfloorheatingsystems.co.uk/products/
For any larger systems with more thermostats, different floors, multiple manifolds, etc please send us the floor plans for a quote.
We also need to know the floor construction for each floor and if possible the manifold locations.
The quote is normally done the same day as we receive the floor plans.
A Cad design will take 1-2 days to do and all the parts are in stock for 1-2 days delivery after payment.
Downward heat losses are approximate 10 % with any underfloor heating system. Therefore it is always best to use some insulation on the FF also.
We recommend a minimum of 30 mm insulation as this will prevent any rooms over heating on the ground floor.
See more floor constructions below;
https://www.underfloorheatingsystems.co.uk/underfloor-heating-design/floor-construction/
This summer , Underfloor Heating Systems Limited are launching a new mixer pack.
Our current mixer pack is with a Reliance Water Controls (RWC) mixer and a Grundfos UPS2 6 m pump.
The next generation pump for the future is the UPM3 from Grundfos as this has 7 m head.
We will continue to use the RWC mixer as this is the market leader.
We have also seen a number of copies of mixers from the far east of the world.
Please be aware that these mixers might look the same, but they do not perform the same.
Mufeng contains other products and information you need, so please check it out.
Our actuators are 230 V made by Jurgen Schlosser in Germany. It takes approximate four minutes for the actuators to open when a programmable Heatmiser room thermostat is calling for heat.
The actuator comes with top and side indicators to show if the actuator is closed or open. Power to the actuator will open the underfloor heating loop.
All our manifolds are made by Watts in Germany to the highest quality possible. We only use stainless steel as the quality is much better than any brass manifolds.
We offer Neo hardwired or NeoAir wireless thermostats that will work with any smart mobile to control the underfloor heating system. A Heatmiser Hub will be provided that connects to your router.
Many companies suggest Overlay boards, but below system is much better as the performance of the wet underfloor heating is much better than any Overlay system;
A thin Superfoil insulation can be used below the mesh. Then, 50 mm liquid screed or fibre screed on top.
For a screeded floor, edge insulation should be installed along the perimeter walls. This not only allows the screed to expand and contract slightly, but also insulates against any heat losses. The edge insulation can be e.g. 20 or 25 mm polyurethane insulation.
Alternatively rolls of edging strip can be purchased and fitted as perimeter insulation. We stock edging strip rolls of fifty metres each and sell them at a price of £ 19 + VAT. We do not include it in our quotes but can supply upon request.
3 core + earth. We also supply wireless thermostats from Heatmiser and the Neo Smart thermostats that will work with any smart mobile device.
Use a minimum of 50mm high density insulation below the pipes and 65 – 75mm of screed on top of the insulation. All installation work must comply with current Building Regulations. Note the screed drying time can be 4 to 6 weeks before the underfloor heating system is operated. The mixing valve needs to be set at minimum temperature when commissioning the system. Increase the temperature by 2 to 3 degrees everyday. This will avoid the screed cracking.
50 mm liquid screed or fibre screed can also be used.
It is recommended to use a pump that can deliver a 6 m head.
We will shortly start to supply the Grundfos UPM3 pump with 7 m head, but we also stock the Grundfos UPS2 pump with 6 m head.
Use the 16×2 mm multilayer pipe for the underfloor heating. The multilayer pipe offers 100 % oxygen diffusion thanks to the aluminium layer.
PEX/AL/PEX pipe is much stronger than any PERT pipe.
Multilayer pipe has one of the highest approvals in the world from the Water Research Council (WRC); 10 bar pressure and 95°C temperature. Even so the multlayer pipe is guaranteed for 10 years within leaving the manufacturer for any damages for which the manufacturer can be blamed. When correctly installed, multilayer pipe will have a working life in excess of 50 years.
The water flow temperature will vary between 35-60°C, depending on the heat losses from the building. If the system operates with thermostatic mixing valves, use 45°C temperature for screeded floors and 55°C temperature for timber suspended and floating floors.
Some heat pumps will work at 35°C which means the pipe spacing needs to be c/c 150 mm.
The system is designed to work with a temperature difference between the flow and the return. The following temperature differences works well with 5,6,7,8,9 and 10°C.
The maximum loop length of 110 m must be used in all installations. It is not advisable to make the loops longer than 110 m. The reason for this is due to the head pressure from the pump, the pump used is only capable of pressurising water through 110m of pipe. 110 m of multilayer pipe will cover an area of approximately 25 m2. A useful note is to always take the feeder pipes into account from the manifolds.
The manifold is supplied with thermostatic option heads on the return and manually regulated flow gauges on the flow manifold. If individual control is needed, actuators can be mounted on the return manifold. The flow gauges on the flow manifold can easily be adjusted by using the key provided and adjusting the nut on the flow manifold before installing the actuators. Normally a 100m loop will have full flow and half flow will be provided for a 50m loop. The flow rate can be seen on the flow flow meters.
Maximum heat output from screeded floors is approximately 100 W/m2, the maximum heat output from timber suspended floor and floating floor is 70 W/m2. With there being higher standards of insulation in new buildings, average heat requirements for many buildings are now below 60 W/m2. For small bathrooms it is standard practice to also install warm water towel rails to give extra heat output as these areas are usually not very large.
The pipe distance from walls should be 100 mm.
The pipe is marked every metre. This makes it very easy to check the length of each loop. When laying the pipe it is important to mark how long each loop is, this is to allow the flow gauges to be easily adjusted to the right levels.
Maximum length for any underfloor heating loop is 110 m.
Delivery of all underfloor heating components is normally 2-3 days from confirmation of your order, subject to availability.
See our delivery options here.
Use carpets with less than 1.5 Tog. Any timber floors need to have a moisture content less than 10 % to avoid shrinkage. If more the timber should be allowed to dry naturally.
Do not use wood on top of wood. Best to use engineered boards – 21 mm max.
Tiles are very good heat conductors.
If required we can supply you with AutoCad design of the underfloor heating layout. There is no charge for the Cad drawing. Also we can provide a comprehensive site visit if the client feels this is necessary.
We always need a drawing first to do a quote and we need to know what the floor construction will be; view our Floor Construction page here.
For smaller systems, see our online shop.
The multilayer pipe has massive range of approvals from all over the world, including WRAS, KIWA and DVGW. The pipe is approved for 10 bar and 95 degree C.
As the multilayer pipe is of very high quality, the pipe is guaranteed to work for in excess of 50 years with a 10 year company insurance backed guarantee.
Our pipe manufacturer is Valsir from Italy – One of the leaders in the world for PEX/AL/PEX pipe for underfloor heating.
The pipe pitch (centres) should be 200 mm. If one room is for example 15 m2, try to use all the 100m of pipe, even if it means to use 150 mm centres. The only consequence of using 150 mm centres is that the system will respond quicker. The same applies if a room of a size 22 m2, try to use 100m of pipe, even if it means to use 225 mm centers. This clearly shows how flexible and cost effective multilayer pipe is when used in an underfloor heating installation.
We always supply a Cad design for the loop layout as long as we have a good PDF drawing, else an hand sketch can be provided.
We normally supply approx two clips (staples) per metre of pipe average. In the straight runs you do not need to clip down the pipe that often, but at the bends where the pressure builds up you normally need several. Hence it works out as about two clips per metre of pipe on average.
Apart from the standard 6cm clips we also stock 4cm clips for situations where the insulation has to be thinner.
The pipe can also be tied to mesh on top of the insulation, where necessary, if the pipe can not be clipped down. Cliprail can also be used. Other methods are to fit th epipe into grooved aluminium heat emission plates or into grooved floating floor panels.
We normally supply approx two clips (staples) per metre of pipe average. In the straight runs you do not need to clip down the pipe that often, but at the bends where the pressure builds up you normally need several. Hence it works out as about two clips per metre of pipe on average.
Apart from the standard 6cm clips we also stock 4cm clips for situations where the insulation has to be thinner.
The pipe can also be tied to mesh on top of the insulation, where necessary, if the pipe can not be clipped down. Cliprail can also be used. Other methods are to fit th epipe into grooved aluminium heat emission plates or into grooved floating floor panels.
We recommend that your underfloor heating is tested immediately before the floor is laid. It is recommended to test the underfloor heating system for 24 hours and using a pressure of 6 bar.
A water pressure test is always better for wet underfloor heating, but if there is a risk for freezing outside temperatures an air test must be performed as else the pipes could get damaged.
Always lay the pipe in heat output importance, for example;
As long as we have an PDF drawing of the property a Cad drawing will be provided for the underfloor heating loops.
Our pipe is a 16 x 2 mm multilayer pipe made by Valsir.
Maximum loop length is 110 m and the pipe spacing for our water underfloor heating system is normally c/c 200 mm.
See instruction in the control pack box. The underfloor heating manifold with connect directly with the mixer pack. Here at Underfloor Heating Systems Ltd we use Reliance Water Controls mixer and a Grundfos UPS2 pump or Grundos UPM3 pump.
The underfloor heating system should be filled with water and fully vented of air. This can best be achieved using mains water pressure through the two end caps. All valves should be closed and the flow end cap connected with a hose to mains water, with the return end cap connected to a hose laid to waste water point. One by one flow and return valves are opened and closed on loop purging them of air.
Are you interested in learning more about Floor Heating Pipe Clips? Contact us today to secure an expert consultation!
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