Area and material
Start with measured area and a local material/installation rate that matches the intended system.
Removal and preparation
Carry separate allowances for demolition, disposal, grinding, patching, moisture work or other substrate preparation where uncertain.
Ancillary work
Transitions, wall base, stair details, furniture moves, protection and temporary access can be meaningful line items.
Contingency
A contingency is not a substitute for investigation, but it can acknowledge uncertainty before the existing floor is opened up.
Commercial flooring decisions depend on the actual substrate, moisture conditions, traffic, cleaning regime, accessibility requirements, fire/building rules, manufacturer instructions and local code. This site is for planning and comparison, not installation instructions.