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Complete step-by-step guide
Installation guide for full-surface floor heating

A professional guide to installing LARX carbon heating film — step by step, from subfloor preparation to first start-up. It covers both dry installation under floating flooring and wet installation under screed. Any handy DIYer or floor layer can manage the installation themselves.

Start the guide
9installation steps
30+ yearslifespan

Floor structure

Carbon film can be installed in two ways. The layer structure differs depending on whether you lay the film dry under floating flooring or wet under screed.

Application directly
under floating flooring

Acoustic insulation LARX CARBON-FILM.COM LARX CARBON-FILM.COM Laminated floor LARX CARBON-FILM.COM
  • 1Any flooring with click system
  • 2PE film 0.2 mm
  • 3LARX CARBON-FILM.COM
  • 4Acoustic insulation
  • 5Reflective separation film

Application
under screed

LARX UHLÍKOVEFÓLIE.CZ Anhydrite/concrete Possible tile adhesive Durable LARX carbon heating Film LARX CARBON-FILM.COM
  • 1Any flooring / tiles
  • 2Anhydrite / concrete / floorboards
  • 3PE film 0.2 mm and separation film
  • 4LARX resistant carbon film
  • 5Reflective separation film
Step-by-step guide

Installation procedure

Follow each step carefully. Click a step to expand the full procedure, tips and warnings.

Step 1 of 9 0 % complete
1
Planning and designMeasure, design the layout and choose the variant

Before you start, plan the layout carefully. Measure the total room area and subtract the footprint of fixed flat-bottomed furniture — built-in wardrobes, kitchen units, bathtubs, shower enclosures. The result is the effective heated area, which determines the number and lengths of film strips.

The film width is fixed at 50 cm and cannot be cut. Design the strips side by side to cover the free area, with a gap of approx. 5–10 cm from walls and fixed objects. Decide whether it will be a dry installation under floating flooring or a wet one under screed. Plan the thermostat location and the routing of the supply leads.

Critical warningDo not place the film under fixed flat-bottomed furniture or appliances. Heat blocking will cause overheating.
Pro tips
  • The film length can only be adjusted at the designated cutting points; the cut is insulated with the included sticker. Never cut the 50 cm width.
  • The strips must not overlap.
  • Choose a floor covering suitable for electric floor heating.
Necessary toolsTape measurePaper and pencilRoom sketch
2
Subfloor preparationClean and level the surface

The subfloor must be clean, dry, level and solid. Remove dust, dirt and sharp objects (pebbles, screws, nails) that could damage the film. Level out any unevenness. A level, dry subfloor is essential for both installation variants.

CautionDo not seal a damp subfloor under the system — moisture is harmful. For concrete slabs at ground level, provide a vapour barrier.
Pro tips
  • Vacuum the subfloor again just before laying.
Necessary toolsVacuum cleanerLevelling compound
3
Reflective and thermal insulationReflective film directs heat upwards

Lay a reflective separation film on the subfloor; it directs the heat upwards into the room instead of into the subfloor. Tape over the film joints.

Dry installationOn top of the reflective film, additionally lay impact-sound insulation (e.g. Arbiton) as a base directly under the carbon film.
Pro tips
  • Thermal insulation significantly reduces running costs and speeds up floor warm-up.
  • Lay the reflective film with the reflective (shiny) side up.
Necessary toolsReflective separation filmImpact-sound insulation (dry variant)Adhesive tapeKnife
4
Laying out and shortening the filmRoll out the strips and adjust them to size

Roll out the carbon film strips according to the sketch — side by side and without overlapping. Leave a gap of approx. 5–10 cm from walls and fixed objects.

Never cut the 50 cm width. The length can only be adjusted at the designated cutting points. Carefully insulate each cut with the included insulating sticker.

Critical warningCut the film only at the designated cutting points and properly insulate each cut. Never cut across the width or outside the marked area — you would damage the heating circuit.
Pro tips
  • Lightly fix the strips to the subfloor with tape so they do not shift during the next steps.
  • Route the supply leads to the thermostat location.
  • Photograph the strip layout before covering — invaluable for future reference.
Necessary toolsScissorsInsulating stickers (included in the kit)Adhesive tapeLayout sketch
5
Electrical connection of the stripsParallel connection and insulation of joints

Connect the individual strips in parallel using cables and clamp connectors crimped with crimping pliers — no other electrical connecting material is needed.

Carefully insulate every joint and copper-strip cut with butyl insulating tape, which prevents moisture ingress and short circuits. Strips can be connected in parallel up to a total output of 2,300 W (10 A circuit breaker, 1.5 mm² wiring).

Critical warningEvery copper-strip joint must be perfectly insulated with butyl tape. Imperfect insulation is a risk of short circuit and fire.
Pro tips
  • Crimp the clamp connectors firmly for reliable contact.
  • Route the supply leads to the thermostat conduit.
Necessary toolsCopper stripClamp connectorsCrimping pliersButyl insulation tape
6
Floor sensor installationPositioning the thermostat NTC sensor

Place the thermostat floor sensor (NTC) in a conduit approx. 30–50 cm from the wall, in a representative spot without furniture. In the conduit it remains replaceable without breaking up the floor.

CautionThe sensor must not lie directly on the heating film — it would measure a distorted temperature and the thermostat would heat incorrectly.
Pro tips
  • If you have a backup sensor, insert it into the same conduit a short distance from the main one.
  • Mark the sensor position on the photo of your sketch.
Necessary toolsFloor sensor with conduitTape
7
Resistance measurement and inspectionVerification before covering the film

Before covering, measure the heating circuit resistance with a digital multimeter and compare it with the value on the film rating label. Also measure the insulation resistance between the leads and earth — it must be infinite (display shows "OL").

Visually inspect all joints and the insulation of the copper-strip cuts.

Critical warningIf the insulation resistance is finite or the measured resistance does not match the rating label, do not cover the system and contact the supplier. A hidden fault is a risk of fire and electric shock.
Pro tips
  • Photograph the multimeter display with the measured values as a permanent record.
Necessary toolsDigital multimeter
8
Covering the filmFloating flooring or screed

How the film is covered depends on the chosen installation variant:

Dry installation — under floating flooringLay a 0.2 mm PE vapour barrier over the film and place the click-type floating flooring directly on it (laminate or vinyl rated for electric floor heating). The floor can be used immediately.
Wet installation — under screedLay a separation PE film over the film and pour anhydrite, concrete or screed. Once the screed has fully cured, lay the final flooring or tiles.
CautionFor wet installation, let the screed fully cure before switching on the heating, according to the screed technology. Do not lay flooring on uncured screed.
Pro tips
  • For the dry variant, make sure the vapour barrier covers the entire film area.
  • When laying the flooring, do not use sharp tools directly above the film.
Necessary toolsPE vapour barrier 0.2 mmFloating flooring (dry)Separation PE + screed (wet)
9
Thermostat connection and commissioningFinal wiring and first start-up

The film supply leads and the floor sensor are connected by a qualified electrician to a thermostat designed for electric floor heating (230 V) with a floor sensor. The thermostat must be on a circuit protected by a 30 mA residual current device (RCD). The thermostat is not included with the film.

Dry installationThe system can be used immediately after connection.
Wet installationSwitch on the heating only after the screed has fully cured and increase the temperature gradually over several days to prevent thermal shock to the screed.
Critical warningThe electrical connection must be made by a qualified electrician. The circuit must be protected by a 30 mA RCD — in bathrooms this is a legal requirement.
Pro tips
  • Program the thermostat according to your daily routine for minimal running costs.
Necessary toolsThermostat with floor sensorWiring diagramWork performed by an electrician