In brief: Underfloor heating consists of several layers: insulation to prevent heat loss downwards, support elements to secure the heating pipes, the heating pipes themselves and the screed, which stores heat and releases it evenly into the room. The chosen floor covering is then installed on top. Planning includes calculating the heat load, selecting the system and creating a pipe layout plan.
Underfloor heating creates an unrivalled sense of comfort. It distributes heat evenly throughout the room, avoids stirring up dust and gives you complete freedom when designing your space, as there are no radiators in the way. To benefit from these advantages, careful planning and an understanding of the correct underfloor heating structure are essential. Whether in a new build or renovation, this modern home heating technology is an investment that pays off.
This guide takes you through the individual layers of underfloor heating, introduces the most common systems and explains the key steps for successful planning and underfloor heating installation.
What is the basic structure of underfloor heating?
Water-based underfloor heating is a multi-layered system integrated directly into the floor structure. Each layer has a specific function to ensure efficient and controlled heat transfer. From bottom to top, the standard structure is as follows:
- Structural floor: The load-bearing base of your floor, usually made of concrete or wood. It must be clean, level and dry.
- Insulation layer: This layer is crucial. It prevents valuable heat from escaping downwards into the ceiling or ground. The insulation boards are usually made of polystyrene (EPS) or polyurethane (PUR). The thickness depends on the energy-efficiency requirements.
- Support system: The system for securing the heating pipes is installed on top of the insulation. This may consist of studded panels, staple panels or hook-and-loop systems that hold the pipes at the planned spacing.
- Heating pipes: The heart of the system. Warm heating water circulates through these plastic or composite pipes, transferring its energy to the surrounding area.
- Heated screed: The screed completely surrounds the heating pipes. It stores heat and distributes it evenly across the entire surface. Its thickness and composition are very important for the heating system to function properly.
- Floor covering: The final covering must be suitable for underfloor heating and conduct heat effectively into the room. Tiles and stone are ideal, but many other materials are also possible.
Additional advice
Do not forget the perimeter insulation strip. This is fitted around all walls before the screed is poured. It separates the screed from the walls, prevents sound bridges and allows the screed to expand as it warms up.
What systems are available?
Depending on the application – a new build, renovation of an older property or simply heating a single room – different systems are available. The choice has a significant impact on the installation height, installation time and costs.
The wet system: The classic choice for new builds
With a wet system, the heating pipes are laid directly in liquid screed. This method provides the best heat transfer and heat storage. After the pipes have been laid, the screed is poured and must then harden and dry, which can take several weeks. There are several ways of securing the pipes in wet systems:
- Staple system: The heating pipes are secured with special staples to an insulation board with a laminated mesh film. It offers flexibility when choosing the pipe spacing.
- Studded panel system: The pipes are simply clipped between the studs of a pre-formed system panel. This enables fast and precise installation.
- Hook-and-loop system: The heating pipes are wrapped with hook-and-loop tape and pressed onto a special hook-and-loop film on the insulation. The system allows very flexible and fast installation.
Underfloor heating and cooling systems use large surfaces to transfer energy and can therefore operate with very small temperature differences relative to the room temperature. This makes them particularly suitable for use with renewable energy.
The dry system: Ideal for renovations
When the installation height is limited or weight is a concern, a dry system is the solution. The heating pipes are laid in pre-formed grooves in system elements made of polystyrene or wood fibre. Heat-conducting plates made of aluminium or steel ensure even heat distribution. Instead of wet screed, dry screed boards are used. This makes installation quick and the floor can be walked on immediately.
The advantages are the low installation height, often just a few centimetres, and the significantly lower weight. This makes the system ideal for timber beam floors in older buildings. The response time is also shorter than with wet systems because there is no heat-storing screed mass.
Electric underfloor heating: The quick solution for small rooms
For individual areas such as the bathroom or kitchen, where you want comfortable warmth quickly, electric underfloor heating is a good option. It consists of thin heating mats or foils that are laid directly in the tile adhesive or beneath the floor covering. Installation is simple and the installation height is minimal.
The main disadvantage is the higher running cost due to electricity consumption. It is therefore usually used as supplementary heating for added comfort rather than as the sole heating system for the entire house. When renovating these rooms, it is often worth reviewing the lighting as well. Modern, slim solutions such as the
or the slightly longer version provide good lighting without taking up much space. Also remember suitable bulbs, such as the for existing installations.
How do you plan your underfloor heating step by step?
Good planning is half the battle. Mistakes made at this stage can be very difficult and costly to correct later. Work through the following points carefully.
Important note
The exact heating load calculation according to DIN EN 12831 is complex and should be carried out by a heating designer or heating engineer. It forms the basis for sizing the entire heating system, not just the underfloor heating.
Needs analysis: heating load and room layout
First, determine the heat requirement (heating load) for each individual room. This value in watts indicates how much heating output is needed to bring the room to the desired temperature even on the coldest days. Factors such as the insulation of the building, window areas, outdoor temperatures and the desired room temperature are included in this calculation.
Choosing the system and determining the build-up height
Based on your building project (new build/renovation) and the calculated heating load, choose the right system. Check the maximum available build-up height from the subfloor to the top of the finished floor. Take door thresholds, stair connections and other structural conditions into account. In a new build, there is usually enough space for an efficient wet system. In older buildings, limited build-up height often means choosing a dry system.
Create an installation plan: heating circuits and spacing
An installation plan is the technical drawing for your underfloor heating. It specifies how the heating pipes are laid in the room.
- Heating circuits: Each room or larger area (over approx. 15 m²) should have its own heating circuit, starting and ending at the manifold. This allows each area to be controlled individually. The length of a single heating circuit should not exceed 100-120 metres in order to avoid excessive pressure loss.
- Pipe spacing: The distance between the heating pipes determines the heat output. In occupied areas, it is often 15-20 cm. In perimeter zones beneath windows or along external walls, the spacing is reduced (e.g. 10 cm) to meet the higher heat demand in these areas.
- Layout pattern: A distinction is made between the spiral (bifilar) and serpentine layouts. The spiral layout ensures the most even surface temperature because the flow and return pipes always run next to each other. It is the standard for living areas.
Expert tip
Take photos of the floor after laying the heating pipes and before the screed is installed. This means you will still know exactly where the pipes run years later. That can be invaluable if you ever need to drill holes in the floor.
What role do screed and flooring play?
Screed and flooring are not just passive layers; they are active parts of the heating system. Their properties have a direct impact on the efficiency and comfort of your underfloor heating.
The screed above the heating system must completely surround the pipes so that it can absorb and release heat effectively. Cement screed is the robust classic, but it requires a long drying time. Calcium sulphate screed (anhydrite screed) flows better, surrounds the pipes optimally and dries faster. Pipe coverage is important: The screed should be at least 4,5 cm above the pipes to ensure good heat distribution and prevent cracking.
Low-temperature heating systems such as underfloor heating offer the highest energy efficiency because heat losses during heat distribution in the building decrease as the system temperature falls.
The flooring should have the lowest possible thermal resistance (max. 0,15 m²K/W). The lower the value, the more easily heat reaches the room. Ceramic tiles, porcelain stoneware and natural stone are ideal partners for underfloor heating. If you prefer wood, laminate or vinyl, always check the product marking and the manufacturer's explicit approval for installation over underfloor heating.
Installation and commissioning: what do you need to consider?
Installing underfloor heating is a major project. While many DIY enthusiasts install the system panels and pipes themselves, some steps must be carried out by professionals. The planning and installation form part of a complex overall system. Modern plumbing and irrigation systems in the home must be perfectly coordinated.
Before the screed is installed, the installer must carry out a pressure test. The installed heating circuits are filled with water or air and pressurised. A report documents that the system remains leak-tight over a specified period. This step is your insurance against leaks in the finished floor.
Once the screed has dried, the so-called functional and readiness-for-cover heating process follows. The heating is gradually increased according to a set procedure. This reduces stresses in the screed and removes residual moisture. Only then may the final flooring be installed. You may need special power tools to prepare the subfloor and install the manifold. And to keep the work area clean, robust tarpaulins and nets are a great help.
A well-planned and professionally installed underfloor heating system is a durable and efficient source of heat that enhances living comfort for decades. It is more than just a heating system—it is a fundamental part of modern, comfortable living.
Frequently asked questions
- How high is the build-up of underfloor heating?
- The build-up height varies considerably depending on the system. Wet systems in new builds often require 9-12 cm, including insulation and screed. Dry systems for renovations are much thinner and can be installed with just 3-5 cm. Electric heating mats have the lowest build-up height, at only a few millimetres.
- Which flooring is best for underfloor heating?
- Floor coverings with low thermal resistance, such as ceramic tiles, natural stone and porcelain stoneware, are ideal. They transfer heat quickly and efficiently into the room. Many modern vinyl and laminate floors, and even some parquet floors, are also suitable. However, always check that the manufacturer has explicitly approved the flooring for use with underfloor heating.
- Can you install underfloor heating yourself?
- Experienced DIYers can install the heating pipes or heating mats themselves. However, connecting the system to the heating manifold and heating system must be carried out by a qualified heating professional to ensure system safety and proper operation.
- What is the difference between wet and dry systems?
- With a wet system, the heating pipes are installed directly in wet screed, which stores the heat. With a dry system, the pipes are laid in prefabricated insulation panels with heat-conducting plates, which are then covered with dry screed panels or the flooring itself. Dry systems are lighter and thinner.
- How long does screed need to dry with underfloor heating?
- Drying time depends on the type and thickness of the screed. Cement screed generally takes around one week per centimetre of thickness to dry, and the heating must not be switched on during the first four weeks. Anhydrite screed dries more quickly. Always follow the manufacturer's instructions and the prescribed heating-up protocol.
You may also be interested in
- Installing underfloor heating: Step-by-step guide
- Calculating underfloor heating: Making the right choice
- Water-based underfloor heating: Benefits & installation
- Flooring for underfloor heating: The key facts
- How does a heating system work? The basics of home heating explained simply
- Installing heating pipes: A DIY guide to efficient heat