Transcript Moisture Mitigation How they work and what to use.  Concrete Open or Close System?  Open system: Slab in contact with earth • Greater.

Moisture Mitigation
How they work and what to use.
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Concrete Open or Close System?
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Open system: Slab in contact with earth
• Greater opportunity for introduction of water post
construction.
• It is prudent to consider any slab of age to be an open
system. (compromised closed system design)
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Close System: Slab separated with a vapor “barrier”
• Recommended within ASTM F710
• Greater protection from introduction of water post
construction, but not bullet proof and often times not
constructed according to ASTM F710.
 Closed
System:
Unfortunately, a vapor barrier’s purpose from a construction point
of view differs from the floor covering industry’s and building
occupier’s perspective. In truth, most vapor barriers at the time of
slab pour are intended to trap the necessary water required for
proper curing. They are typically specified at 6ml polyethylene
sheeting which is not an adequate barrier for long term protection
from moisture migration.
 Grade:
Below Grade
Moisture Mitigation Systems
may not compatible with all
slab designs.
Care must be taken to select
the system best suited not
only for the MVER/PH
conditions, but also for the
type of slab construction, its
underlying structure (open or
closed), and etc.
A perforated pan slab pour
above grade is considered an
“open” system for example.
On Grade
Above Grade
 Concrete:
where is the water?
 Why do floors fail?
 Types of Mitigation Systems
 Potential failures
Water Sources
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Free Water
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Bound Water
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Chemically binds and never leaves
Hydrostatic pressure
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Water of convenience needed for slab finishing
Water forced into and upward through the slab
Lateral Migration
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Water introduction into the slab from an outside
source
Once the slab is poured and finished, “bleed water” runs off and the
remaining water within the slab is defined as:
Free water
 This water is found within the
capillaries of the slab and will
begin to evaporate if given the
correct conditions.
Bound water
 This is the water that is
permanently bound as an integral
part of the concrete slab.
How water enters a building
HYDROSTATIC PRESSURE
How water enters a building
LATERAL MIGRATION
How water moves through a slab
As a Vapor
Water in the form of a vapor is
moved from the bottom to the
surface through the capillaries
within the slab. Higher
porosity (over watered slab)
will allow this process to occur
more freely. Water comes into
contact with the adhesive/slab
bond line and attacks the
integrity of the adhesive.
How water moves through a slab
As a Liquid
Water has filled the capillaries completely just as a soaked sponge is
completely wet.
Why is moisture a problem?
Alkalinity’s effect
 As the water vapor migrates up through the slab, it will condense
and form liquid water at the bond line between the slab and the
adhesive. This solution then becomes alkaline and will harm acrylic
adhesives.
What is PH?
 PH is the measure of Hydrogen ions (acid) or Hydroxide ions
(alkalinity) in a water-based system. PH is measured on a
logarithmic scale from 0(acid) to 7(neutral) to 14(alkaline). Because
the PH scale is logarithmic, each point represents a 10 fold
increase in alkalinity. A PH of 9 is 10 times more alkaline than a PH
of 8. Gerflor does not recommend a PH higher than 8.5.

Vapor Pressure
Even with adhesives that are resistant to alkalinity and moisture, as
the adhesive is bonded to the surface of the slab pressure can build
beyond the cohesive strength of the adhesive and release. The
typical evidence of this is random bubbling.
It will usually start in an area or areas and gradually work its way
outward as the condition remains or worsens.
 Corrective
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Measures:
Remove and re-pour slab
Topically applied mitigation system
Install slip sheet membrane
 Topically Applied
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Mitigation Systems
Penetrating
Epoxy Coating
Dense Cementitious Overlay
Sealers
Single system approach (adhesive=
moisture/ph resistance and bonding agent)
 Penetrating
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Sealers
Penetrating type reactive sealers are liquid applied treatments that
chemically react with the concrete reducing the MVER and bind alkali
below the bond line.
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These are typically silicate in nature (sodium, lithium, or potassium)
Some concrete mixtures will affect the efficacy of these types of
sealants in relation to moisture/ph suppression and bonding
compatibility with flooring adhesives.
Silicate type treatments are considered by some with much less
confidence than other topically applied products.
 Epoxy
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Coatings
There are single and multiple coat systems available.
Many systems designed for very high moisture/ph conditions
Designed to reduce MVER to a tolerable level at the bond line.
Isolates PH from flooring system.
Typical that slab must be abraded through grinding or shot blasting.
Typical that a cementitious over lay is required due to type of adhesive
used for the floor covering and/or repair trenching caused by concrete
surface preparation.
May include a broadcast.
 Dense
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Cementitious Overlay
Usually requires preparation of the slab’s surface
Primer is applied prior to top coat
Highly densified cementitious layer is poured (may be self-leveling)
Floor patching as needed to bring to floor coverings required levelness
benchmark.
Isolates slab from floor covering system.
 Top
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Coat Sealers
Typically used for lower MVER/PH conditions (approx. 8 lbs)
May or may not require slab surface preparation depending upon
surface condition of the slab (porosity, existing residues/sealers, etc.)
Designed to reduce MVER/PH to a tolerable level.
Not typically recommended for open slab systems.
May or may not be recommended for below grade slabs.
One of the least expensive systems to apply.
Typically a high solids water based product.
May be “elastomeric”. Caution should be applied to these in
combination with certain types of resilient floor covering.
 Single
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System Approach
New adhesive products designed to seal the slab and act as a
bonding agent in one step.
• Water based acrylic adhesive
• Moisture cure urethane adhesive
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Economical
Designed for lower MVER/PH conditions
May or may not be designed for certain types of floor covering
May or may not be recommended for open slab systems.
 Slip
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Sheet Membranes
Typically incorporate the use of a urethane adhesive in
combination with a low permeance vapor barrier.
Essentially “free floats” accommodating minor cracks and joints.
Typically shot blasting or grinding is not required.
Not necessarily compatible with all flooring systems.
Effectively isolates floor covering away from the slab alleviating
build up of vapor pressure. (vapor moves laterally)
PH resistant
 Pitfalls
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of selection
Generally price driven as the discovery of the problem doesn’t occur
until just prior to installation of the floor covering.
Lack of investigation.
Incomplete system that does not include accommodations for cracks or
joints.
Warranties
System requires “certification” prior to purchase and application
Cost
Incorrect system chosen for existing conditions
Liability/Support if failure occurs
Incorrect application or slab preparation
 Who
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pays?
Conditions above the tolerance level of the floor covering system
on new construction projects usually involves incorrect design
and/or construction. Unfortunately, this is often not discovered
until just prior to installation of the floor covering. As contractors,
we can not assess who is the responsible party to cover
potential mitigation costs, but it is certain that these expenses
should not be absorbed by the floor covering contractor.
Contractors must be very cautious also with existing slabs. Due
diligence through careful inspection, investigation, and testing
according to industry practices and the mitigation suppliers
recommendations is compulsory prior to making any
recommendation for a specific mitigation system.

The problem is not a problem…
until it becomes a problem.
Caution is strongly advised if a contractor makes a personal
recommendation for any moisture mitigation system. Choose a system that
is appropriate for the conditions and/or potential conditions. Select a
system that has a history of performance and customer service in the event
of a claim. All to often, moisture mitigation providers are quick to lay claim
to contractor error before performing due diligence to discover the actual
problem and offer a means to correct it. If a mitigation provider requires
training, do not short cut this requirement. If experience or confidence is
lacking, it is prudent to provide a list of mitigation providers to the General
Contractor, Architect, or End User that they can contact for direct
communication and recommendation.
 Testing
prior to recommendation:
Most moisture mitigation systems require traditional moisture
testing as outlined in ASTM F1869 commonly referred to as
Calcium Chloride tests. These determine the MVER (moisture
vapor emission rate) of the surface of the slab at the time of
testing. Other tests may also be applicable including the “mat”
test, or the In-Situ probe test (ASTM F2170). All tests should be
performed by an experienced testing professional (a third party
not financially vested into the project) complying to the required
testing protocol and completely documenting the results. These
results should be forwarded to the GC, Architect, and/or End
User prior to selection of the mitigation system to be used.
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