maxit floor Moisture Environment Concepts  
   
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Background
Risk Factors
Damage Processes
When tp Use Adhesives?
Drying
Humidity Measurement
Questions

Damage Processes

Floor-specific Damage Processes

Examples of damage processes specific to different types of floor include:
  • Adhesives are broken down by alkalis.
  • Casein is broken down to ammonia, that discolours parquet, for example.
  • Plasticisers from PVC floor-coverings are broken down.
  • Parquet swells on exposure to damp.
  • Linoleum swells, and blisters may form.
  • Gypsum board becomes mouldy at the skirting boards.
Criteria for drying according to the porous nature of floor-covering materials


 Floor-covering materials can generally be divided into three groups:

  1. Non-porous floor-coverings.
  2. Floor-coverings porous.
  3. Floor-coverings highly porous.
1. Floor-coverings inporous

For example, stone and clinker brick . These can withstand being in a damp, alkaline environment for long periods. RHCRIT=100% (CM>4% for cementitious levelling/screed products). But note that glass mosaic tiles and some stone and ceramic tiles may react to alkalis and thereby produce large amounts of alkali silica gel which can 'spring' the tiles. In this case RH must be reduced or a low-alkali substrate be used. At high humidity you should also be aware of the risk that salts may be carried up through the joints between the ceramic tiles and precipitate out on the floor surface.

2. Floor-coverings porous
Examples of these are PVC and linoleum flooring, that are usually stuck down to the substrate and on their own can withstand higher humidity levels than wood. PVC floorings can be used in bathrooms where they will be exposed to moisture over long periods. The reason why adhesives and flooring materials can be damaged by the substrate is that moisture can act as a transporter of alkalinity from the concrete substrate. Alkaline hydroxyl (OH–) ions are transported to the adhesive and the flooring, and break them down by saponification. Breakdown products, normally alcohols, are released and emitted to the environment. When the effect is minor, it is first noticed upon breaking up the floor-covering. In more severe cases there will be a smell from the floor. The alcohols produced have a strong smell and are regarded as a symptom of a 'sick floor'. However the alcohols themselves are not toxic in the concentrations that can arise from a sick floor.

In such cases it is beneficial to cover the concrete substrate with a levelling compound. A floor-levelling compound has significantly lower alkalinity (pH value) than concrete. A levelling layer is thus an effective way of creating a less alkaline environment at the contact surface between substrate and covering, and so reducing risks of breakdown and emissions.

3. Floor-coverings highly porous
For example, wood and cork. Wood is highly porous and swells when it comes into contact with it. If wood is exposed to moisture for long periods and in sufficient quantities, it may suffer growth of mould and fungi. Wooden floors cannot therefore be laid on substrates with an RH higher than 60% (CM<3.0% for cementitious levelling/screed products). This normally requires some form of moisture protection if other measures are not specified in the floor supplier's instructions.