Workmen applying KOSTER VAP I 2000 Waterproof floor by KOSTER Spreading KOSTER VAP I 2000

Moisture Control Systems


Vapour Barrier Systems

Solve the problem of water vapour in concrete slabs causing vinyl or resin flooring failure by using Koster VAP I 2000. This proven vapour barrier system can be applied to new build or existing concrete and will stop moisture from permeating through the concrete and compromising the flooring, thus preventing the need for costly remedial work.

The Koster Water Vapour Control System (Koster VAP I 2000) was successfully introduced to the American Market in 1992 and has an impressive track record with thousands of satisfied customers including The Pentagon, where the system was installed as a vapour barrier on the concrete floors in the hallways, offices and washrooms.

KOSTER VAP I 2000 Application

Why is water vapour an issue?

Flooring failures due to water vapour in concrete floor slabs have been plaguing the construction industry for decades, causing millions of pounds worth of damage. Typical damage patterns (indicating a serious failure of the flooring system) can be blisters in epoxy coatings, bubbles in sheet flooring, unsightly staining at seams, adhesive bond failure, loose, curling and cracking VCT (vinyl composite tile), warped wood floors and damp and mould infested carpets.

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Re-emulsification of adhesive...

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Typical blistering...

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...resulting in downtime

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...containing highly alkaline, dangerous liquid


Where does the moisture in floors come from?

Water is present in the ground almost everywhere, as moisture or in liquid form as ground water. A concrete floor slab or basement slab can come into contact with water where it is immersed, or merely in contact with moist ground. Moisture can originate from a lower laying ground water table rising in the ground due to capillary action.

When a concrete slab is in direct contact with the moisture in the ground, capillary action transports that moisture into the concrete. Water that is present in the ground can also turn into water vapour and rise through the ground until it comes into contact with the bottom of a concrete slab into which it can then penetrate.

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Water is one of the key ingredients of concrete. At the time concrete is made, it contains liquid water. While part of that water is used up in the hydration process, another part of it remains in the concrete and evapourates over time. The more water that is added into concrete at the time it is produced or during curing, the longer it is going to take to dry to a level that is acceptable for a flooring system . In fast track construction programs this can lead to expensive delays. Air conditioning systems de-humidify the air in buildings. Since vapour will move from an area of

high concentration to an area of low concentration, a stream of water vapour from the floor slab into the air is set in motion. Water vapour readings should always be taken at a time when the heating, ventilation and air-conditioning systems (HVAC) have been turned on in order to assess the vapour drive of the building under normal use. Further sources of water can be broken pipes under a slab, spills onto concrete, building use such as kitchens or washroom areas, cleaning and maintenance, rain and snow, ambient relative humidity and condensate forming on the concrete due to condensation.


What other factors can have an influence on water vapour in floors?

In new buildings:-

  1. Missing or damaged vapour barriers underneath slabs with ground contact, prolonging the drying out of floor slabs.
  2. Fast track construction often requires flooring applicators to install flooring systems before the concrete has had sufficient time to dry.
  3. Lightweight concrete is frequently used for upper levels in order to design slimmer structures. It requires a higher water to cement ratio than standard concrete and will take longer to dry to an acceptable level.
  4. The use of blended cements can result in considerably longer drying times for concrete than the use of standard cements.

In existing buildings:-

  1. Renovation of flooring systems: In the past, most flooring systems were breathable and the adhesives used contained solvents and asbestos which were not affected by moisture and alkalinity. Many flooring systems which are installed today are non-breathable or only very slightly breathable and the adhesives used have limits regarding the alkalinity they can be exposed to. Once a vapour tight flooring system is applied, the vapour is trapped inside the concrete. That sets the precondition for the water vapour damage mechanism to start, eventually leading to a failure of the adhesive and the flooring.
  2. Changing environmental conditions: Moisture conditions underneath a floor slab can change over time, for example with the changing seasons. Heavy rainfalls over a long time period can cause a raised water table. The raised water table brings with it an increased amounts of water vapour. If the floor slab was built on grade without a functioning vapour barrier, it now becomes exposed to a higher level of vapour drive.

How does water vapour harm flooring systems?


1. Concrete without floor covering


As long as the water vapour can simply pass through the concrete, it does not do much harm although it can act as a transport mechanism for salts of various types causing efflorescence on the surface of the concrete.

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2. Concrete with floor covering


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When a flooring system is installed, it typically has lower vapour permeability than concrete. The water vapour can no longer pass through the concrete due to the installation of the flooring system. As a result the amount of water vapour that is present in the slab will slowly rise. This can be measured as an increase in the relative humidity in the concrete. Wood floors can expand and buckle when exposed to moisture over a period of time. Also, microbial growth can develop under floor coverings leading to health hazards for the occupants. Various coatings and adhesives will de-bond when the moisture level underneath the impermeable flooring becomes too high. In cases where different patching compounds have been used on top of each other underneath a vapour tight floor covering, they can react with each other in the presence of accumulated moisture. If concrete contains aggregate that is susceptible to Alkali Silica Reaction (ASR), the moisture now present in concrete can cause this to start, leading to the destruction of the concrete. Also, in old concrete which is already affected by carbonation, moisture can cause reinforcement steel that has been embedded in the concrete to start corroding.



3. Developement of high alkalinity

Once the relative humidity at the surface of a concrete slab becomes high, temperatures below the dew point of water in the surface area will cause condensation within the surface layer. Such temperature regimes can be caused by the operation of air conditioning systems. Now the pores of the concrete below the surface are saturated with water. Adhesives that bond floor coverings to the concrete can degrade and fail as a result of the high pH and moisture present in the concrete. The high alkalinity that develops in the surface of the concrete due to moisture can also discolour floor coverings. Cured concrete contains soluble salts of calcium, potassium and sodium. In contact with water, these salts form hydroxides. Once dissolved in water, high alkaline conditions develop with pH readings up to 14. Potassium hydroxide in particular is known to be very aggressive against mineral building materials such as silica sands.


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4. Developement of blisters


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Once a highly alkaline condensation layer has developed underneath the surface of a tightly adhered vapour tight floor covering, the primer and the adhesive are directly exposed to this. This is the prerequisite for the formation of liquid filled blisters, which are frequently observed as part of a failure of a flooring system. Such blisters are often referred to as �osmotic blisters� although osmosis as a damage mechanism is much debated in the scientific community. Typically with this type of damage mechanism it will usually takes 3 to 6 months for coatings to delaminate. The exact time frame in which this delamination takes place depends on the level of vapour drive and the composition of the coating as well as that of the concrete. The liquid in blisters can have a pH of 14.


How water vapour problems can be solved!