Separate wear from failure
A faded line can still be firmly bonded, while a bright line may be peeling at the edge. Walk the complete layout and record fading, edge lift, contamination, cracking and repairs separately. This prevents a cosmetic problem being treated like a substrate failure, or a bonding problem being hidden beneath another coat.
Identify the existing system
Do not assume every old line is the same chemistry as the floor finish beneath it. Check maintenance records, product labels and previous contractor information where available. Compatibility matters on sealed timber and specialist resilient systems. If the coating history is unknown, use a controlled test area and obtain product guidance.
Clean without damaging the surface
Dust, polish, silicone residues, grease and sports grip products can undermine adhesion. Use the floor manufacturer’s approved cleaning method. Aggressive abrasion or solvent cleaning can damage a finish that was otherwise sound, so preparation must match the substrate and coating system.
Approve a test patch
A small test patch should reproduce the intended cleaning, masking, coating and cure conditions. Inspect appearance, edge definition and adhesion after the stated cure period. If the layout is changing, include the old-line hiding method in the trial rather than testing new paint on a clean area only.