Heating screed with underfloor heating

Heating screed with underfloor heating

Heating screed with underfloor heating: screed

Who builds a house, is often under time pressure. One tradesman sits at the back of the other and can not get to work until the previous work has been completed. But the client himself would like to move in as soon as possible. After all, it puts a double burden on him during the construction period. A house construction costs money, the bank wants first installments or commitment rates and the rent for the previous apartment must be paid in addition. Time is money.

Nevertheless, one should not rush or break over the knee. Certain processes need their time. This also includes the drying and curing of cast concrete parts, such as ceilings or screed, and the heating of heating screed.

Anyone who does not pay close attention to the specifications and gives the screed time to dry or heat up can cause damage and, above all, additional costs. Our notes should explain why the screed is necessary to heat up and help to avoid mistakes.

Screed drying with or without underfloor heating

In house construction, in addition to CA screeds (calcium sulphate screeds), mainly CT screeds (cement screeds) are used. Its special advantage lies above all in its good resistance to moisture and its suitability as a heating screed.

When "drying" cement screed is to be noted, however, that it does not dry at all for hardening, but chemically sets. This means that installed screed needs the moisture to fully cure. Only when the screed is accessible, which is usually reached after 24 hours, may be aired and thus the excess water can be withdrawn. If you are already helped to "dry" before, the screed can not set properly, causing tensions and cracks.

Remember: After applying the screed, keep windows and doors closed for two days or cover the screed with a foil. Then it can be ventilated and dried. Only after 21 days is cement screed fully cured and allowed to heat up.

Why do I have to heat the screed?

From the physics lessons, everyone is sure that substances expand in heat and contract again in the cold. How strong depends on the so-called coefficient of expansion. But we do not have to penetrate that topic so deeply.

Heating screed with underfloor heating: screed

Underfloor heating before screed placement

Like any fabric screed expands under heat. In the screed, however, there is the underfloor heating, which should be installed as widely as possible at the same distance, but the screed never heated to 100% evenly. In addition, the screed contains sand or gravel in different grain sizes, which expand at different speeds. All this ensures that tensions arise that can cause the screed to break.

Therefore, it is important to heat the cement screed slowly. The ingredients are given the opportunity to slowly and evenly expand and adapt to the environment. As a result, voltages can be compensated and reduced. After the screed has been heated slowly after the heating protocol, the material has adapted and can then be heated up faster. The slow heating by means of underfloor heating is, so to speak, a settling in phase - the "muscles" are stretched and warmed up. Only then can they be properly used.

When do I have to heat the screed?

A "When do I have to heat up the heating screed?" there is not any! When building a house or installing screed with underfloor heating, however, the desire for a rapid construction progress and the compulsory adherence to the heating screed drying time or hardening meet.

Therefore, the question should not be "When do I have to...?" but "When may I...?" ring. The question is relatively easy to answer - When the screed has hardened. Given are 21 days for this. If you are not under time pressure, you can wait 28 days for security. Thereafter, the heating of the cement screed may begin.

How long do I have to heat the screed?

Like the time required to cure the screed, it is also necessary to heat the screed on underfloor heating. One speaks of thefunctional heating.

The minimum layer thicknesses of screeds are specified in DIN 18560 and therefore hardly differ in the case of cement screeds in detached houses with typical stresses. On average, the heating pipes should cover about 45 mm, resulting in a screed thickness of 60 to 70 mm for a pipe diameter of 15 to 20 mm.

With different additives in the screed, the manufacturer's specifications may differ slightly, but fundamentally the following can Daily heating program for screed be used:

Heating screed with underfloor heating: underfloor

Heating screed on floor heating
  1. Flow temperature ofHeat to 25° C
  2. Flow temperature ofKeep at 25° C
  3. Flow temperature ofKeep at 25° C
  4. Flow temperature ofHeat to 30° C
  5. Flow temperature ofHeat to 35° C
  6. Flow temperature ofHeat to 40° C
  7. Flow temperature ofHeat 45° C
  8. Flow temperature ofHeat 55° C
  9. Flow temperature ofKeep 55° C
  10. Flow temperature ofKeep 55° C
  11. Flow temperature ofKeep 55° C
  12. Flow temperature ofLower 45° C
  13. Flow temperature ofLower 35° C
  14. Flow temperature ofLower 25° C

When heating the screed it is necessary to ventilate well. After curing for the first 21 days, excess moisture already escapes, but it can take a few days to even weeks to reach maturity. Decisive for heating screed Drying time is, of course, the weather, the ventilation and also the moisture in the environment that results from further masonry and plastering work.

To check the maturity, which is defined depending on the floor covering, a residual moisture meter should be used. This clearly shows how much moisture is still contained in the screed and whether already a floor covering may be laid.

What does the screed heating program do?

Since the screed thicknesses are always very similar, heating up the screed with a floor heating is almost always the same. Many heating manufacturers therefore equip their heaters with a screed heating program that is similar or even looks exactly like the time and temperature diagram shown.

The automatic heating of the screed offers the advantage that you can make no mistake and the heating must not be manually adjusted daily. However, it is important to check whether the sequence of the heating program matches the information on the screed. If necessary, a consultation is necessary.

Do I need a heating protocol?

Whether you really need a heating protocol depends on your own performance. Do screed work and screed drying with the underfloor heating on your own, you can indeed make a heat-up protocol for yourself, but in case of damage you can hardly claim for damages or warranty claims.

However, things are different when companies are involved in this work.Here is a heating protocol your proof that all time limits for screed hardening and screed heating (duration, flow temperatures) or the heating screed drying time were met. It is therefore particularly important that the date is entered and confirmed for each work step. This is the only way to assert warranty claims if cracks appear in the screed after heating up.

Heating screed with underfloor heating: screed

Without heat-up protocol no warranty claims

The heating protocol should contain the following points:

  • customer
  • Project
  • Construction phase (floor gang, individual rooms or part of the building)
  • executed screed works (description, type of heating screed...)
  • Date log and overview of all steps to the screed works and the heating program or a manual heating control
  • special notes
  • Signature / stamp of the Minutes, inspector or executing company

The heating protocol can be designed individually. However, many companies already have their own templates and the Internet also offers many examples that can be used and adapted.

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Video Board: Underfloor Heating and Flowing Screed Install