How to Properly Secure and Fix the TC 10 Cable Before Pouring Concrete
Why proper fixing of TC 10 cable is crucial before concrete pouring
The resistance heating cable TC 10 is among the most reliable solutions for floor heating in Slovakia – simple installation, no electronics in the floor, long service life. However, it has one property that determines whether the system will function problem-free for decades, or after just a few weeks of pouring, a technician will ask "why isn't it heating?": the cable must be mechanically firmly and reliably fastened to the base at the moment of concrete pouring (slab), in a precisely defined spacing, without any allowed extension or shortening of the route, and without any mechanical stress on the conductive core and insulation.
Concrete pouring is a process that causes real mechanical stress on the cable – the slab material has weight, it pushes, shifts during compaction and vibration, and if the cable is not sufficiently fixed, it can shift, lift, cross with an adjacent branch, or in the worst case, cause mechanical damage to the insulation. That is why fixing the cable is a separate, important part of the installation – it is not just "sticking a strip," but a technological step with its own rules.
This article focuses exclusively on the phase of fixing and securing the TC 10 cable before concrete pouring – as a continuation of previous steps (power selection, spacing calculation, actual installation), which you can find in other articles in the Knowledge Center. Here we focus on how to literally "pin" the cable to the base so that it survives the concrete pouring without damage.
Which fixing methods for TC 10 cable are used in practice
In Slovak conditions, when installing resistance heating cables of type TC 10, we encounter practically four basic methods of securing. Each has its advantages, disadvantages, and typical use depending on the base to which the cable is laid.
1. Mounting (fixing) strips with hooks
The most common and at the same time most recommended solution. These are plastic perforated strips (bands) with ridge teeth or hooks, which are first attached to the base (screws into thermal insulation, or glued with double-sided tape/adhesive mortar to concrete), and then the cable is simply clicked into them at the desired spacing. The advantage is the speed of installation, precise adherence to spacing, and the fact that the cable is firmly clamped on both sides of the arc, so it cannot shift during pouring.
2. Laying into reinforcing (mesh) grid
A classic and proven solution, especially for thicker slabs and renovations, where the cable is simply fastened with tie bands (tying wire or plastic clips) directly to the bars of the reinforcing mesh laid on the thermal insulation. The mesh also serves as reinforcement for the slab, so this method combines two functions in one step.
3. Fixing on system insulation boards with protrusions
These are profiled polystyrene or polyurethane boards with a regular grid of protrusions (pins) on the surface. The cable is simply pressed between the protrusions, which securely hold it from both sides without the need for additional fastening material. This method is fast, but it requires the purchase of specialized system base material, which increases the cost of the construction.
4. Combined fixing – strips + clips + tape
In practice, we very often encounter a combination of the above methods – for example, strips on straight sections, additional fastening with aluminum or textile tape at corners and when crossing expansion joints, to ensure the cable cannot move at all in critical areas.
Spacing and fixing scheme of the cable on the mounting strip
In the diagram you can see the typical laying of the cable in a "snake-like" (zigzag) pattern between two opposite fixing strips. The cable is securely clicked into the teeth of the strip at each point of the arc, which prevents its lateral and downward movement during slab compaction. The spacing R is selected according to the required power per m² – the detailed calculation can be found in the article on the spacing of the TC 10 cable laying.
Step-by-step procedure – fixing the cable before concrete pouring
The following procedure is based on common practice when installing resistance cables TC 10 into anhydrite and cement slabs. We recommend following it in the exact order, as each step builds on the previous one.
Step 1 – Preparation and inspection of the base
The base (thermal insulation, existing slab or waterproofing) must be flat, clean, free of sharp protrusions, stones, mortar residues or metal rods. Any sharp object under the cable is a potential point of piercing the insulation under slab load.
Step 2 – Laying out and fixing the fixing strips
The strips are placed parallel, usually at distances of 50–100 cm from each other (depending on the room length and width), and perpendicular to the direction of cable laying. They are either screwed directly into the polystyrene insulation or glued with double-sided tape/adhesive to the concrete base. It is important that the strips are parallel to each other and at the same height level – otherwise the cable will bend at the uneven point and the local spacing will change.
Step 3 – Unwinding and laying out the cable "dry"
Before you start fixing the cable, we recommend unwinding it completely and laying it out freely on the prepared route without fixing, just to check that the calculated cable length fits the area exactly and that the cable does not have to bend under a smaller radius than allowed by the manufacturer (minimum bending radius for TC 10 is usually 6 times the cable diameter, in practice about 4-5 cm).
Step 4 – Fixing the cable into the strips or to the mesh
The cable is clicked into the teeth of the strip (or tied to the mesh with plastic clips) at the exact turning points of the meander. Clips or strip teeth must never clamp the conductive core with such force that it deforms the insulation – the cable should freely "settle," not be forcibly pulled.
Step 5 – Fixing the arcs and corners with additional tape
In places where the cable meanders (180° turns), mechanical stress during slab pouring is greatest – the material flows there and can "lift" the cable. These areas are therefore recommended to be additionally covered with aluminum or textile mounting tape, or to be additionally fastened with an extra clip compared to the normal spacing on the straight section.
Step 6 – Fixing the supply and connecting cable
The cold supply cable (non-heating part, the junction between the heating and supply conductor) must be laid in such a way that the junction is not in a place of direct mechanical load (e.g. under furniture, at the location of future partitions) and at the same time fixed as firmly as the heating part – the junction is the most critical part of the entire system and its movement during concrete pouring can cause microcracks in the surrounding material.
Step 7 – Final visual and electrical inspection before pouring
Only after the entire route is fully fixed, the insulation resistance and electrical resistance of the heating circuit are measured – this topic is covered in detail in a separate article on testing the functionality of the cable before and after pouring the slab. Without this measurement, concrete pouring must never be started.
Cross-section of the floor construction – where exactly the cable lies
In the cross-section, it is visible that the cable lies exactly on the top edge of the fixing strip, which is anchored into the thermal insulation. Above the cable, the screed thickness should be at least 3 cm (recommended value for a classic cement screed), while below it is the insulation that prevents heat loss downwards. Precisely this layer between the strip and the surface is what creates pressure on the cable during the concrete pouring – and therefore the fixation must be sufficiently rigid.
Minimum bending radius and cable protection during fixing
One of the most common mistakes during the fixing of the TC 10 cable is its too sharp bending at the turn of the meander, especially when trying to "fit" more cable meters into a smaller area (for example, in a bathroom around the toilet or bathtub). The manufacturer specifies the minimum allowed bending radius of the cable – for a standard diameter of resistive heating cables, it is approximately 4–5 cm. Below this limit, there is a risk of mechanical damage to the copper core or cracks in the insulation, which may manifest as a local short circuit or a broken circuit after pouring the screed.
Therefore, when fixing into the strip, it is necessary to choose such a spacing between the teeth that ensures a natural arc of the cable without bending. In very tight spacing (for example, in high power on a small area), it is advisable to use strips with denser teeth, where the cable arc is supported multiple times and not just at two extreme points.
Fixing in specific areas – expansion joints, transitions, corners
During concrete pouring, expansion (shrinkage) joints are usually made in the floor, dividing the screed into smaller sections to prevent uncontrolled cracking during volume changes. The TC 10 cable should never run directly in the place of a planned expansion joint – in practice, we avoid this already during the route design, but if a collision occurs, the cable must be protected in the transition area with a protective sleeve (PVC or metal grommet) and fixed in such a way that the cable jacket is not directly stressed during movement of the screed in the joint.
Similarly, in room corners and at door transitions (where the cable often runs very close to the door frame), it is advisable to reinforce the fixing – use a shorter spacing of clips or an additional strip, because precisely in the corners, there is a local accumulation of material and higher pressure during the pouring of the screed.
Checking the fixed cable – what to look for just before concrete pouring
Before the concrete workers arrive with the mixer or pump, we recommend performing a thorough visual and mechanical check of the entire route. In practice, the following control procedure has proven effective:
- Walking the entire cable route barefoot or in soft shoes – the cable must not move freely from side to side under slight foot pressure.
- Visual check of spacing – in no place should two cable branches touch or cross each other (except when passing through the cold/cold feed section).
- Checking the height of the cable above the subfloor – the cable should lie directly on the surface of the insulation, not "floating" in the air between the strips, because during the pouring of the screed, it could shift upwards or sideways due to hydrostatic pressure.
- Checking the connectors and the end of the cable (cold joint) – it must be outside the heated area and securely fixed, ideally additionally protected by a protective tube.
- Photographic documentation of the entire route with a measuring tape in the frame – this is a step that many installers underestimate, but during future floor reconstruction (e.g., drilling into the screed), the photo documentation is the only reliable basis for where the cable exactly runs.
After this check, the resistance of the heating branch and the insulation resistance to ground should be measured – these values should be recorded in the installation protocol and compared with the values after pouring and hardening of the screed. A detailed measurement procedure is discussed in a separate article on testing the functionality of the TC 10 cable.
How fixing affects the concrete pouring itself
During the pouring of the screed (regardless of whether it is a classic cement screed 6–8 cm thick or a thin-layer anhydrite screed with a minimum cable cover of only 3–4 cm), a simple rule applies: the thinner the layer above the cable, the greater the emphasis must be placed on the quality of the fixing. In thin anhydrite screeds, where the cable cover is minimal, there is a risk that the cable will "float" toward the surface if the fixing is insufficient, and after sanding or when laying tiles, the cable may become visible or even damaged by a drill during anchoring.
In the case of a classic thicker concrete screed, the situation is milder, but even there, during compaction with a vibrating float or poking the screed with a rod, the cable can shift if it is not firmly tied. We therefore recommend monitoring during the pouring of the screed to ensure that the workers with the pump hose or float do not touch the cable route directly, and pour the concrete in small sections gradually, not all at once in one place – this minimizes the risk of local displacement of the fixed cable.
Practical experience from installations – what happens most often
From our experience with the installation of dozens of TC 10 systems, we know that the most problems are not caused by the cable itself, but precisely by insufficient or incorrect fixing before pouring. We present a few typical scenarios:
Scenario 1 – Fixing only with adhesive tape on smooth polystyrene
Sometimes, in an attempt to save time or money, the cable is simply glued with ordinary adhesive tape directly onto the polystyrene without using mounting strips. The problem occurs during the pouring of the screed – the liquid mixture lifts the tape and the cable shifts, resulting in uneven spacing and local "cold" spots in the floor after completion. We recommend always using system fixing strips or mesh, with tape being only an additional reinforcement in critical points.
Scenario 2 – Too large a distance between fixing points
If the fixing strips are placed too far apart from each other (e.g., more than 100 cm), the cable between them "sags" and can move freely in the middle of the section. During concreting, such a section of cable "floats" and creates an uneven coverage – in one place the cable is just under the surface, in another it is deeper near the insulation. The recommended distance between strips is 50–80 cm, depending on the stiffness of the cable and the weight of the screed.
Scenario 3 – Insufficient protection of the supply cable junction
The junction between the cold supply wire and the heating cable is a spot with a larger diameter and less flexibility. If it is not properly fixed (e.g., only loosely placed on the insulation), during the pouring of the screed it may shift or be stressed in tension, which over the years may lead to mechanical loosening of the connection and failure. We recommend always fixing the junction at least at two points in its vicinity.
Scenario 4 – Incorrect spacing when passing through bathroom corners
When laying around the corners of a bathtub or WC pan, the cable is often compressed too tightly into a small area, which during fixing leads to exceeding the minimum bending radius. In practice, we have seen cases where the damaged cable sheath in this way caused a short circuit between the core and the protective braid after pouring the screed, which led to tripping of the residual current device and the need to cut the screed to locate the fault. This can be easily avoided by carefully adhering to the minimum bending radius already during fixing.
Table of approximate values for fixing cable TC 10
| Parameter | Recommended value |
|---|---|
| Spacing of fixing strips (transverse) | 50 – 80 cm |
| Minimum bending radius of the cable | 4 – 5 cm (approx. 6x cable diameter) |
| Minimum cable coverage by the screed | 3 cm (cement screed), 2.5–3 cm (anhydrite) |
| Distance of the cable from walls / expansion joints | min. 5–10 cm |
| Additional fixing in curves | an extra strip or clip compared to the straight section |
Selecting the correct cable power before fixing
Fixing makes sense only as well as the cable was selected and placed according to the calculation of area and power. In the atria.sk offer you will find cable TC 10 in several power ranges, which differ in length and total power – from smaller powers for bathrooms and smaller rooms up to larger powers for larger areas:
- HAKL TC 10/ 1030 W 2x connection cable – suitable for smaller areas, e.g. bathrooms or hallways
- HAKL TC 10/ 1100 W 2x connection cable – similar power category, slightly longer cable
- HAKL TC 10/ 1900 W 2x connection cable – medium area, living spaces
- HAKL TC 10/ 2200 W 2x connection cable – larger rooms, e.g. living rooms
- HAKL TC 10/ 2410 W 2x connection cable – the highest power in this range, larger areas
The full range can be found in the category Heating cables TC 10, where you can select a specific model according to the calculated area and the required power per m². An exact calculation of power according to area can be found in the article on selecting the power of HAKL TC 10 cable according to m², and the calculation of laying spacing can be found in the article on the laying spacing of TC 10 cable.
Resistance measurement diagram before pouring the screed
The measured resistance values of the heating branch (in ohms) and insulation resistance (in megaohms, measured with an insulation tester / megohmmeter) must match the data on the cable label, or must not significantly differ from the values measured before fixing. A significant difference indicates cable damage already during installation or fixing – in such a case, pouring must not be carried out until the cause is identified and eliminated.
Connection of fixing to other installation steps
Cable fixing is not an isolated step – it follows the correct selection of power and spacing, and precedes the actual pouring of the screed and later testing of functionality. We therefore recommend considering the entire installation process as a chain, where the rule applies: good calculation of area and power → correct laying spacing → thorough fixing → inspection and measurement → pouring with concrete → re-measurement after hardening. If you skip or underestimate any of these steps, the risk of failure increases significantly regardless of how high-quality a cable you used.
A detailed step-by-step description of the entire installation from start to finish is covered in the article Installation of heating cable TC 10 into the screed step by step, and the most common errors during the entire implementation are covered in a separate article Most common errors during installation of resistance cables TC 10 – both are recommended to be read as a supplement to this text.
Frequently asked questions about fixing cable TC 10 before pouring concrete
Can I fix cable TC 10 only with adhesive tape without mounting strips?
Technically yes, sometimes it is done in small and simple areas, but it is not a recommended procedure. Adhesive tape may gradually loosen when in contact with wet concrete or screed and the cable may shift. Mounting strips or mesh provide significantly more reliable and even fixing across the entire area.
What material of fixing strips is most suitable?
In practice, plastic (PVC or polypropylene) strips with hooks or teeth are most commonly used, which are UV and temperature stable and do not react with the screed material. Metal clips are not commonly used in floor heating, as corrosion and local heat conduction in another direction is a risk.
What to do if the cable is slightly damaged (cut sheath) during fixing?
Minor surface damage to the sheath without affecting the conductive core can sometimes be treated with special insulating sealant intended for repairing heating cables, but we recommend contacting the supplier or manufacturer and have the damage evaluated by a specialist. If there is a suspicion of damage to the core, the cable must not be poured in that section without repair, as a short circuit may occur after commissioning.
Is it necessary to fix the cold supply cable as well, or only the heating part?
Yes, the entire route including the cold supply cable and the junction must be fixed, at least in the section where it is located in the floor. A freely placed supply cable may shift during pouring of the screed and stress the junction in tension.
How soon after fixing the cable can I start with concrete pouring?
Concrete pouring can follow practically immediately after the completion of fixing and successful electrical inspection (resistance measurement). There is no technological break between fixing and pouring, on the contrary, it is recommended not to leave the fixed cable exposed to movement of people on the site for a long time, in order to reduce the risk of mechanical damage before pouring.
Can I use the same fixing method for anhydrite and cement screed?
Yes, the principle of fixing is the same, only the minimum cable coverage (which is usually slightly smaller in anhydrite) and the pouring method differ (anhydrite is usually pumped mechanically in one layer, while cement screed is often poured and compacted manually) – however, the same principle of thorough and even fixing across the entire surface applies to both technologies.
Conclusion
Fixing the TC 10 cable before concreting may seem like a simple formality at first glance, but in reality, it determines the long-term reliability of the entire floor heating system. Properly placed and secured mounting rails, adherence to the minimum bending radius, sufficient securing of connectors, and thorough inspection before concreting are investments of just a few minutes of work that prevent months of cutting into the screed and searching for faults after the floor is completed. When choosing a specific cable model, we recommend basing your decision on an accurate calculation of area and power, and carrying out the next step – fixing – thoroughly according to the guidelines provided in this article. You can find the full range of resistance cables in the category Heating cables TC 10, where you can select the specific power and cable length according to your area.
Do you have a question about this topic?
Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.