concrete floors are vulnerable to moisture and suffer from different
detrimental influence of moisture such as lifting tile off the floor, rotting hardwood,
damping carpet, coating delamination and many more.
are not only disrupting functions of the building due to maintenance operations
but also costly. Therefore, it is recommended to implement necessary measures
to stop moisture in concrete floors.
techniques are available which can be applied based on the condition under
consideration. By and large, every problem can be tackled provided that the
source of the problem is identified. On this base, suitable prevention method or
combination of methods are specified to cut the anticipated source of moisture
in given concrete floor.
Free water in
concrete and rising moisture from below concrete are the source of moisture.
Factors that lead to moisture accumulation in concrete and subsequent related
problems include fast track construction schedule which does not allow free
water to evaporate naturally, inadequate moisture protection, and wet
techniques are available for slabs that is already constructed and experienced moisture
and newly constructed slabs.
of Moisture in Concrete
- Free water in concrete
- Moisture rising from below the slab
of Moisture Accumulation in Concrete
- Wet Building Sites
- Fast-Track Construction
- Inaccurate, Insufficient or
Misinterpreted Moisture Tests
- Inadequate Sub-Slab
- Changing materials
Methods Used to Stop Moisture in Concrete Floors
There are different techniques used for stopping moisture in concrete floors. These techniques are classified into two groups include those which are used before slabs construction and methods used for existing slabs:
Before Slab Construction
1. Low-permeance Vapor Barrier or Retarder
A Low-permeance vapor Barrier or retarder
can effectively keep below-slab moisture from reaching the flooring system. In this
technique, a layer of sand with certain thickness is placed, after that, a strong
and highly durable plastic such as polyethylene is laid, then another layer of sand
is installed above the plastic sheet. After that, the construction of concrete
floor can be carried out.
Any material used below slab to prevent
the movement of moisture from ground into slab fall in this category of moisture
2. Allow Natural Drying of Concrete Slab
Sometimes, providing adequate time
for natural drying of concrete slab would solve the problem. In this case the
concrete slab shall be tested prior to the installation of tiles, coatings, or
3. Keep Excavation Free of Water
Keep below grade excavations free of
water to prevent potential reservoirs of moisture that can migrate upward
through slabs. Excessive moisture below concrete slabs can cause structural
degradation of soil bearing strengths, and swelling and shrinkage of soil. These
can adversely affect a concrete slab on grade.
After Slab Construction
Apply Damping Agent for Existing
In this method, damping agent (such
as liquid epoxy damp proof membrane) is applied for an existing concrete floor
system. It is used for slabs that suffered moisture problems due to lack of moisture
prevention means or failure of moisture prevention system.
The damping agent creates an
impermeable layer and hence keep moisture in concrete slab. Not only does it
provide visually good surface finish to the floor but also it can be applied without
any concern regarding drying the concrete slab.
Application procedure involves clean concrete surface from dirt and then apply the damping agent using roller and brush. It may be required to apply multiple layer, but each layer shall be allowed to be set before applying the next layer. The number of layers is based on the amount of moisture in concrete.