A service bay floor carries oil, solvents, tire drag, cart abrasion and lift pad loads, under wash-down water that keeps it wet daily. For the contractor PM and owner's rep, it covers review, blocks, grit sequence, wear zones, drainage, slip, sampling and handover. Targets: dry PTV at least 36, wet DCOF at least 0.42, 60 degree gloss.

Why polished concrete suits service bays

Bay slabs are cast monolithically with the frame; the surface is the base, not a coating. Cutting back laitance and closing pores with densifier leaves no film oil or solvent can lift. Five zones share one floor: lift bays, alignment racks, tire bays, wash-down lanes and parts corners.

Loads are not uniform. A vehicle spreads weight through four tires, but a two-post lift transfers it through two or four jack pads on small areas, while carts roll the same path daily. A honed slab stands this contact; drag lanes are chosen for abrasion, not sheen.

Base survey and oil solvent penetration

Before machinery enters, the manager records each zone: slab age, finish, prior coatings, patches, cracks, joints, mortar and stains. Oil-soaked pockets are probed; hydrocarbon millimetres into the paste weakens bonding, ground back before diamond stages. A CSP 1-2 surface after a light pass needs profiling or patching.

Work proceeds only with room RH at 75-80% and slab surface at 10-30 degrees Celsius. Below the cold end densifier drags; above the warm end it flashes off and clouds. Drainage fall and sealant are noted for the required slip class.

Work blocks and outage scheduling

Finishes run in scheduled blocks, not one open floor. The shop splits into 200-400 m2 blocks, each with entry path, extraction line and cleanup corner; wet wash-down and dry lift bays are separate. A 3-4 hour after-hours window fits one grinding or resin stage; densifier seals overnight.

At least one bay stays open for urgent repairs; vehicles move to a staging strip so tires do not roll fresh lanes. Drains are protected, sockets covered, each closed bay signed out at the morning meeting. The schedule lists area, stage, window, crew and release party.

Grit sequence and densifier dilution

Stages run metal to resin with full overlaps. Metal starts 16 or 20 grit to cut laitance and expose soft patches, then 30 and 40 grit level the grain; grit changes only after a straightedge shows no marks. Resin runs 100, 200, 400, 800, to 1500 or 3000; an 800 scratch cannot be erased at 1500. Lanes overlap 100-150 mm; densifier 1:64 about 15 ml/L or 1:128 about 8 ml/L.

Point loads and tire wear zones

Jack pads contact a small slab area, so the survey records each pad position and soundness below. Hollow areas near pads are checked or patched before lift cycles; a void can settle after finishing and crack the sheen. Tire-turning lanes wear first as tires scrub one patch each rotation.

Wear zones are mapped: scrub circles, cart drag lines, drop spots and access strips. They get a penetrating guard against oil staining without peeling film; general areas refresh on 3-5 years, high-drag zones on 2-3 years. Spot wear is re-ground locally, not full-bay recoated.

Slope drainage and wet slip criteria

Wash-down bays fall to drains at 1.5-2.0% gradient, so standing water does not carry oil film onto dry bays. The floor is finished before grates are refitted; drains and sumps are covered to catch slurry, slope rechecked after polish. Wet lanes get a coarser honed profile.

Readings are taken under the lift, wash-down inlet, beside the drain, threshold. Dry PTV is at least 36; wet PTV runs 10-20 points below dry, wet DCOF at least 0.42. Wet areas grade R10 to R12. A shiny dry bay can still fail wet grip, so acceptance rests on wet readings.

Acceptance sampling and repair checklist

The standard is agreed on paper first, each threshold tied to a reading, not the loose word smooth. Sampling is one reading per 30-50 m2, plus lifts, drains, thresholds. Sheen reads on a 60 degree meter; adjacent zones differ up to 5 units, over 15 means rework. Inspection uses 300-500 lux oblique light; entries record block, date, value, signature.

• Dull or cloudy patches are circled on the plan; soft spots or fast-drying densifier checked, resin stages re-ground to match sheen.
• White residue means densifier dried on top: a light wet pass at 400-800 grit; if hard, drop to 200 grit first, refine back up.
• Scratches are logged by position and depth; most carry grit from tires or tools, fixed by spot refresh, not full regrind.
• Wet slip complaints are checked against PTV and DCOF; class, texture or signage agreed in writing before regrind.
• Joints, thresholds, pad edges are hand-finished; edge match recorded, hollow or delaminated areas flagged for repair.

Handover briefing and maintenance

On handover the contractor delivers the finish schedule, grit order, products, dilution rates, joint treatment, records, maintenance note. The manager walks each bay with the owner's rep, showing reading points. Every block needs a signed sheet; open items carry a date and party.

Disputes follow the written criterion and recorded readings, not the day's impression. Routine care is sweeping, prompt spill cleanup, guard refresh on 3-5 years general or 2-3 years high drag. The rep leaves a wear-zone map, inspection points, renewal dates.