Page 82 - CFJ_Apr26

SECTOR FOCUS SUBFLOORS & SCREEDS

the condition of the subfloor will need Prime importance
to be assessed once old floorcoverings Once satisfied that the subfloor
have been removed. It may be is sound, smooth and dry, or an
discovered that the subfloor is cracked appropriate moisture management
or damaged, in which case extra solution is in place, the application
preparation will be required. In most of an appropriate floor smoothing
cases, cracks as deep as 50mm can be compound will create a uniform,
filled with a floor repair compound. smooth surface over which to install
Subfloors may also be contaminated the final floorcovering. In most cases
with oil, grease or other chemicals, it will be essential to prime a surface
necessitating mechanical preparation beforehand. This promotes the optimum
by grinding, abrading or grit blasting performance characteristics of the
before applying other floor preparation smoothing compound and, when used
Neil Sanders talks through the products. Contractors should refer over absorbent subfloors, such as
concrete, prevents moisture being
necessary preparation procedures to British Standard (BS) 8204 for drawn from the smoothing compound
guidance on testing if it is possible to
to achieve a fl awless fl ooring fi nish mechanically prepare concrete bases too rapidly.
for the receipt of in-situ floorings where When working over raised access
THE STAGES contamination is present. Old adhesive panels, cement-based primers, such
as F Ball’s Stopgap Fill and Prime,
OF SUBFLOOR residues will need to be removed by are available that fill the gaps at
mechanical means unless a smoothing
PREPARATION compound that is suitable for use over the joints between the panels while
old adhesive residues will be used. Any simultaneously priming the subfloor.
other contaminants that may prevent The product can also be applied to
HE application of a smoothing adhesion, such as wet trade waste or mechanically fixed and glued P5 flooring
Tcompound is recommended to create debris, should also be cleaned off. grade chipboard prior to the application
a smooth base for floorcoverings as Dealing with damp of a recommended smoothing
compound, removing the need to
part of any flooring installation. Equally Contractors must take care to ensure overboard the subfloor with plywood.
important for ensuring installations that the substrate is dry enough to
look as good as possible for years to proceed with a flooring installation. Smoothing compound selection
come is properly preparing the subfloor Whether the result of rising damp Finally, contractors should then take
beforehand. or residual construction moisture, time to ensure that they select the
Although undertaking proper subfloor unmanaged subfloor moisture can optimum smoothing compound for a
preparation should be routine practice, attack adhesives and floorcoverings, particular situation.
neglecting to do so often results in floor possibly causing complete floor failure. For example, smoothing compounds
failure, the leading cause of which is still For this reason, F Ball recommends with high compressive strength should
unmanaged excess subfloor moisture. that a moisture test is conducted to be used where floors will be subject
The following steps are essential determine subfloor relative humidity to heavy loads or high foot traffic. For
for creating a suitable base for the (RH) levels as part of any flooring contractors working to tight timescales,
installation of floorcoverings. installation. A calibrated digital fast-drying smoothing compounds are
available that will be walk-on hard from
Initial preparations hygrometer will give accurate readings just 30 minutes and ready to receive
The first stage in any flooring installation of subfloor moisture levels as a measure floorcoverings in as little as 45 minutes
should be making sure the subfloor is of relative humidity (RH). Where relative after application.
suitably sound and smooth. If a newly humidity of the subfloor is 75% or above Only by following these steps will
installed screed is present, contractors (65% for wood flooring installations), a you meet the highest standards for
will need to ensure that any laitance, moisture management solution must be flooring installations and have the
the crust of cement and fine aggregates installed to prevent subfloor moisture peace of mind that comes with being
that forms on the surface of the screed rising up to the level of the floorcovering assured of avoiding costly floor failures
as it dries, is ground off. If not removed, and causing floor failure. – F Ball guarantees that its products
laitance can cause subsequently applied F Ball recommends the use of a will perform for the entire lifetime
smoothing compounds to de-bond from two-part epoxy waterproof surface of a flooring installation, providing
the substrate, potentially causing floor membrane system, such as Stopgap the advised subfloor preparation and
failure. The normal method of removing F77, which cures rapidly (approximately installation procedures are followed. 
laitance is using a rotary sanding or three hours at an ambient temperature www.f-ball.co.uk
abrading machine. of 20deg C create a barrier against Neil Sanders is technical director at
If the project is part of a refurbishment, moisture where RH values are up to 98%. F Ball and Co

‘If the project is part of a refurbishment, the condition of the subfloor
will need to be assessed once old floorcoverings have been removed’

82 CFJ April 2026 www.contractflooringjournal.co.uk
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