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How to Stop Moisture in Concrete Floor?
Madeh
Izat Hamakareem
These problems 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.
Several 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 construction site.
Moisture prevention techniques are available for slabs that is
already constructed and experienced moisture and newly constructed slabs.
Sources of Moisture in Concrete Floors
1.
Free water in
concrete
2.
Moisture rising from
below the slab
Causes of Moisture in Concrete Floors
1.
Wet Building Sites
2.
Fast-Track
Construction Schedules
3.
Inaccurate,
Insufficient or Misinterpreted Moisture Tests
4.
Inadequate Sub-Slab
Moisture Protection
5.
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 prevention method.
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 paints.
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
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.
Moisture
Prevention Agent for Floor Surface
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.
Madeh is a Structural Engineer who works as Assistant Lecturer in
Koya University. He is the author, editor and partner at theconstructor.org.
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