Anhydrite screed aftercare

  • Access
    • Anhydrite Liquid screed can usually accept foot traffic after 24–48 hours. However heavy site traffic is expected, it is advisable to temporarily protect these areas with plywood sheets or similar these should be removed after required use to allow for drying.
    • The screed material should be allowed to cure undisturbed for the first 24-48 hour period. No foot or site traffic should be allowed. Traditional curing membranes are not necessary but loss of moisture should be controlled during the first 24-48 hours.
    • Temporary sheeting should be applied to windows and/or door openings where not installed, Direct sunlight must be avoided during the first 24-48 hour curing period. This can be avoided by covering windows or large expanse openings with black poly sheeting or similar and removed after 48hrs.
  • Drying
    • It is important to note that drying times relate to ambient humidity, temperature and number of air changes. In general, liquid screed installed as an un-bonded system dries at a rate of 1mm per day for the first 40mm of depth and 0.5mm per day for any depth over and above this. This is provided a temperature of 20°C is maintained and 65% relative humidity.
    • Where drying temperatures are high and humidity is low, drying time will be less. Unlike conventional cement/sand screeds, dehumidifiers may be used to accelerate drying. These should only be used two to five days after placing.
    • Where under floor heating is installed this can be used to decrease drying times but should only be used after the first seven days. The heating system temperature should be built up gradually at a rate of five degrees per day.
    • Prior to the installation of a floor covering, liquid screed must have dried to an approved level. For moisture sensitive coverings the code of practice value is stated as 75% relative humidity, which equates to 0.5% moisture content by mass. Below this value impermeable floor finishes may be applied.
  • After placement screed care
    • It is essential to avoid any further water ingress to the screed flooring as this will slow the drying period significantly, To achieve the stated drying times the following practice should be observed Open all windows and door if possible to gain good ventilation, this will help in the drying process and should be repeated daily, a typical 50mm thick screed under ideal conditions will dry at a rate of 1mm per day for the first 40 days and 1/2mm per day thereafter (60 days in total from initial placement).

Cemfloor screed aftercare

  • Preparation for final floor covering
    • Cemfloor is a cementitious levelling screed and no laitance will form on its surface.
    • Prior to application of the floor covering the screed should be buffed and be checked for moisture content. A residual moisture content of less than 2.5% (75% RH) forbonded floor coverings is required prior to covering.
    • Cemfloor is a cementitious levelling screed and no laitance will form on its surface.
    • Prior to application of the floor covering the screed should be buffed and be checked for moisture content. A residual moisture content of less than 2.5% (75% RH) forbonded floor coverings is required prior to covering.
    • Priming of the screed is not necessary prior to application of the final floor covering.
    • Cemfloor screed may be ready for tiling in as little as 510 days (approx. 14-16 days for heated screeds) and may take up to 21 days for bonded wooden floor coverings. In all instances a moisture check should be carried out prior to covering. A hydro hood may be used to check relative humidity, and a carbide bomb test may be used to test for residual moisture.
  • Site conditions
    • Cemfloor is a superior quality cementitious levelling screed. Its performance and finish quality is second to none, but ultimately depends on the conditions in which it was installed and the conditions during the period following its installation.
    • During the screed installation and for the following 24-84hours, the following requirements must be met:
      The area where the screed is to be installed must be frost free and not subjected to temperatures below 5°C or above 30°C.
      The surface of the newly installed screed must be protected from draughts and direct sunlight.
      The temperature of the area(s) where the screed was laid must not fall below 5°C
    • Following the initial 24 hours(48 hours in winter) after installation the following should be undertaken:
      Open windows and doors on the building to create good cross ventilation and air circulation. This will help to accelerate the drying process.
      Please note a typical 50mm screed will dry to a moisture level of 2.5% in approximately 15-21 days. This however is dependent on site conditions and may dry even sooner.
  • Force drying
    • Force drying of screeds is possible and will dramatically reduce drying times.
    • Force Drying Unlike other conventional screeds, Cemfloor can be forced dried by using the under-floor heating system (if present) or by using a dehumidifier.
  • Force drying – commissioning under floor heating
    • Cemfloor can be force dried using the under-floor heating system, once the following steps are adhered to:
      The under-floor heating system may be commissioned and turned on after seven days of installation of Cemfloor screed.
      Begin commissioning of the under-floor heating system with a water temperature no greater than 25°C and maintain this temperature for three days, On the fourth day the temperature of the water in the under floor heating system may be increased to temperatures no greater than 55°C and kept at this level for at least four days.
      During this process ventilation of the room areas is essential to ensure a low air humidity level is maintained. A relative humidity level of 65% or less should be maintained. Ventilate by opening windows on opposite sides of the building.Continue the above procedure until a moisture level of 2.5%or less (5% for tiling in certain circumstances) is achieved.
  • Moisture testing
    • Hair Hygrometer Method (RH) - The British Standard for testing a base to receive a resilient floor covering is to use a hair hygrometer to the method defined in BS8203:2001.
    • This provides a non-destructive test method and will give results for Relative Humidity near to 75% (which is generally the required limit for floor finishes) Above this level of moisture the hair hygrometer may not always provide a meaningful reading. For correct results, the BS8023 method must be strictly adhered to, including the use of a correctly sized and insulated box sealed to the floor, a sufficiently long test for equilibrium to be reached and the use (where appropriate) of an impervious sheet around the instrument.

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