F. Ball Subfloor Preparation Brochure - Flipbook - Page 11
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Final Checks
Hardeners and surface sealers frequently interfere with
adhesion and should have been removed by one of the
methods described above.
Prior to coating or topping, concrete or screeds must first
be: free of all contamination and laitance; strong enough
to support the coating or topping under the conditions for
which the floor is designed. Moisture levels must also be
below 75% RH (less than 65% RH for wood floors), 2.5%
total moisture by gravimetric, carbide bomb or speed test
methods before proceeding with the installation.
Concrete and calcium sulphate screeds must be left for
construction moisture to dry out before floor coverings
are laid. If there is insufficient time to allow the base
to dry naturally or if there is no protection from
moisture from the ground, bases with solid Relative
Humidity (RH) readings greater than 75% RH (65%
RH for solid wood floors) should be treated with the
appropriate Stopgap Waterproof Surface Membrane
(WSM), following preparation of the concrete or sand/
cement screed detailed. New concrete and sand/cement
screeds must be left for at least 7 days after placing
before being treated with an appropriate WSM.
Stopgap Isolator Membrane can be used in certain
situations as a fast track alternative for damp floors.
The measurement of construction moisture can
also be undertaken using the carbide bomb method.
Readings of less than 2.5% for all cement based
subfloors and less than 0.5% for Calcium Sulphate
subfloors must be obtained.
Immediately prior to applying any coating, topping
or adhesive, ensure that dust from any preparation
method employed is removed by vacuuming.
Preparing concrete may be a dusty operation therefore
appropriate PPE should be worn and good ventilation
should be provided. Protection of walls, furniture and
equipment should be planned.
Residues or spillages of other trades such as plaster,
paint, cement, oil (and sometimes roofing tar) are
frequently present in new constructions and should be
removed. Plaster and cement can be chipped up and
wire brushed. Paint should be mechanically removed.
Oil, fats and grease cannot be removed by washing.
If such contaminants have penetrated into the surface
(which is usually the case) the only way of removing
them is mechanically.
Adhesive residue removed by grinding
This means dust-free shot blasting, scarifying, scabbling
or hot compressed air blasting. Remedial work in meat
processing and engineering plants, for example, remains
a very difficult problem. Removing the contaminated
concrete and re-screeding may be the only solution.
Cores may be taken to determine the depth of penetration
and can assist in deciding on whether or not it is possible
to prepare a surface for overlaying. It may be necessary
to carry out adhesion tests to ensure adequate adhesion
is obtained on a contaminated surface.
In certain circumstances the presence of oil may stain
the new decorative floor covering. If water flows under
partitions, walls, cover mouldings, equipment bases or
furniture, these areas will take longer to dry out and may
delay the installation. Putting paper or polythene sheet
on the floor to keep it clean can retard the drying time.
If old concrete has never been overlaid or painted
it should be treated as new concrete. More emphasis
must be placed on cleaning and repairing any cracks,
holes or eroded areas. Often the best procedure is to
remove all contaminated and unsound concrete.
If necessary, repairs to damaged floors should be
carried out using products such as Stopgap 400 or
Stopgap 460 Exterior Repair Compound prior to applying
floor smoothing compounds (please contact our Technical
Service Department for further details). The specific
concrete repair material must be checked for compatibility
with the surfacing system and be of suitable strength for
the environment of the finished floor.
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