Page 92 - CFJ_Dec25

ADVICE & INFORMATION

Surface prep can make or break a floor

Shotblasting: Steel shot is propelled bonding. and can cause chemical incompatibility.
at high velocity onto the concrete Once the main work is complete, Once the substrate has been assessed,
surface. The residue is extracted into a removal and disposal follow. Industrial the appropriate level of preparation
filtration unit or vacuum, and the shot vacuum extraction is a very important can be determined. Today’s ‘advanced’
is separated and reclaimed. This leaves step to minimise dust and debris – not smoothing compounds can be applied
an open-textured, profiled surface with just for the operatives, but also for over old bitumen residues, as well
the previous layers removed. The speed the surrounding environment. Many as firmly bonded unglazed ceramic,
and size of the shot, as well as the type machines now feature on-tool dust terrazzo, and non-polished quarry
of material being removed, determine extraction. tiles – though cleaning and removal of
the effectiveness of the process. When the substrate is properly contaminants still apply.
Shotblasting isn’t suitable for materials prepared, it allows subsequent layers Some moisture-tolerant smoothing
exceeding 2-3 mm in thickness or for to perform to their full potential. Failing compounds don’t require a primer
surfaces that are uneven, soft, or wet. to remove contaminants can affect how thanks to their high adhesion and low
Grinding: Single or multiple diamond materials react and increase the risk of
heads rotate to level, clean, and smooth failure. shrinkage properties. However, when
the substrate. Diamond grinding is used Next steps applying to porous substrates, priming
to remove high spots or uneven joints up • Primers: These improve adhesion absorbent surfaces is beneficial.
to around 3 mm. and prevent issues such as pinholes It reduces preferential absorption,
Scarifying: Uses cutting elements to or dusting. They seal the subfloor minimises pinholing, extends working
aggressively remove, groove, texture, and enhance the bond between the time, and helps achieve the ideal surface
and level the substrate. Within the subfloor and the new flooring or finish.
rotating drum, the type and size of the smoothing compound. Ultimately, careful assessment
cutting elements determine the depth • Damp proof membranes and vapour provides the foundation for the best
and profile of the cut. barriers: These prevent moisture from decision – helping to mitigate risk and
Sanding: While the above processes affecting the smoothing compound, deliver a properly prepared substrate
mainly apply to cementitious bases, for adhesive, and floorcovering. that supports the floor covering
timber-based substrates sanding or Contamination can otherwise prevent throughout its lifespan. 
planing is the appropriate method. The proper adhesion to the substrate. rob.russell@bostik.com
goal is again to remove contaminants • Old adhesive residues: These are often www.bostik-profloor.co.uk
and leave a clean surface ready for too soft to support additional layers Rob Russell is technical consultant, Bostik UK

‘If a weak layer isn’t removed, the
overall strength of the installation
will only ever be as strong as its
weakest point’

The home of professionals working in the
DOMESTIC FLOORING TRADE national institute of carpet & floorlayers

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92 CFJ December 2025 www.contractflooringjournal.co.uk
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