Every anti-slip coating works the same physical trick: interrupting the lubricating film between sole and floor with peaks the film cannot bridge. The chemistry carries the peaks; the peaks do the gripping.

The three delivery methods:

1. Pre-mixed grit coatings — aggregate (typically fine aluminium oxide or polymer bead) factory-blended into a one- or two-pack paint: stir, roll, done. Texture is moderate and even; the DIY and light-commercial mainstay.
2. Broadcast systems — grit scattered ('broadcast') onto a wet resin coat, then locked with a seal coat: texture is selectable by grit size and density, from fine tooth to aggressive profile — the industrial standard, because the installer controls the grip precisely and can zone it.
3. Structured/textured coatings — thick-bodied products that roller or trowel into a raised pattern without loose grit: rubberised deck paints, textured polyurethanes — favoured on metal stairs, vehicle decks, and where shed grit would matter.

What separates a rated floor from a rough one: aggregate hardness (aluminium oxide keeps cutting for years; sand rounds off), anchoring depth (grit locked by a top coat outlasts grit riding in one film), and measured outcomes — proper products publish slip values (PTV/R-class) at stated build, turning 'feels grippy' into a specification. The base chemistry — epoxy, PU, acrylic — then sets everything else about the floor: bond, chemical resistance, and lifespan, exactly as it would unfilled.

The same intersection logic as every slip decision — water/contaminant × gradient × consequence — mapped to the places coatings specifically serve:

1. Ramps and slopes — pedestrian and trolley ramps, loading banks, car-park ramps: gradient converts any film into a slide; broadcast systems with coarse grit are the standard cure.
2. Wet-process floors — wash bays, kitchens' back corridors, dairies, breweries, pool plant rooms: permanently wet resin floors carry their grip in the coating because nothing else stays effective.
3. External walkways, fire escapes, and metal stairs — steel and timber outdoors under rain and frost: textured deck coatings and GRP-style systems own this niche; smooth-painted steel checker plate is a known accident generator once worn.
4. Thresholds and transition zones — where feet arrive wet onto smooth interiors: an anti-slip band at doorways beats coating whole halls.
5. Workshops and plant rooms — oil mist plus smooth concrete or gloss epoxy: grit-zoned lanes around machines and along walk routes.
6. Public-access duty — anywhere liability meets weather: entrances, jetties, boat decks, playground surrounds.

And where not to blanket it: clean, dry, flat interiors gain nothing but cleaning burden from aggressive texture (the R13-overkill principle); food-prep zones balance grip against washability grade by grade; and display floors wanting subtle insurance use fine polymer-bead additives rather than visible grit. Zone the grip to the hazard map — the coating format makes zoning literally paintable.

Yes — aftermarket additives are a legitimate route, with clear rules about when they suffice and when they don't:

How it works: anti-slip additives (polymer micro-beads, fine aluminium oxide, or crushed glass medias) stir into compatible paints and clear sealers at stated doses — typically 5–10% by volume — and roll on with the coating, curing as dispersed peaks in the film. Over a sound existing floor, one gritted maintenance coat converts a slick surface for the cost of a can and an additive pack.

Where the additive route genuinely works: refreshing garage and workshop floors during scheduled recoats; adding insurance texture to porch and step paints; converting smooth sealed concrete with a gritted clear coat; and zoning — a gritted lane painted through a smooth floor.

Its honest limits:

1. The base coat must be sound — grit in paint peels exactly as fast as the paint; additives fix slipperiness, not adhesion.
2. Suspension discipline: beads settle in the tray — stir continually or the first metres get all the grip and the last get gloss.
3. Texture ceiling: stirred-in additives top out at moderate grip; genuinely wet, oily, or sloped duties need broadcast systems where grit density isn't limited by what a film can carry.
4. Wear cycle: grip lives in one film, so it wears with that film — recoat cycles come sooner than anchored broadcast systems.

The decision shorthand: additive-in-paint for upgrading adequate floors; purpose-made broadcast or textured systems for solving actual slip problems — and if an incident log or a rating target exists, skip straight to the rated system.

Grit grade is the grip-versus-livability dial, and choosing deliberately avoids both accidents and regret:

Fine (polymer beads, fine oxide ~50–100 µm): barely visible, kind to bare feet and knees, mops normally. Grip gain is real but moderate — right for domestic wet rooms' surrounds, retail insurance, gritted clear coats over decorative floors. Wrong for oil or slopes.

Medium (oxide/quartz ~0.2–0.5 mm): the workhorse band — obvious texture underhand, definite wet grip, cleanable with deck brush or machine. Standard for workshops, ramps at modest gradients, external walkways, commercial kitchens' general zones. The default when unsure.

Coarse (0.7–2 mm broadcast): aggressive profile that grips through oil, mud, and standing water on serious gradients — loading ramps, wash bays, agricultural and marine decks. The costs are genuine: harsh on knees and dropped hands, hostile to mopping (brush/hose cleaning territory), eats mop heads and sole rubber, and visually industrial.

Matching rules of thumb: match grade to the worst credible contaminant on the surface (water → medium; oil/grease → coarse); drop one grade where bare skin contact is routine; rise one grade on gradients over ~5°; and mix grades by zone — coarse on the ramp itself, medium on its flat approaches, fine where the corridor resumes — because a floor's grip profile should map its hazard profile, not average it.

And whatever the grade: sample panel first. A square metre cured on site, walked wet in the actual footwear of the actual users, settles in five minutes what datasheets argue about — and shows the cleaning reality before the whole floor commits to it.

The resin rules apply, plus texture-specific craft:

1. Prep as the chemistry demands: degrease-grind-vacuum for concrete (see epoxy prep — nothing changes because grit is coming); abrade and prime metal with the system's metal primer; sound, keyed existing coatings for overcoats. Slip coatings live hard lives — bond failures under texture are ugly and unfixable.
2. Prime and body coats per system, un-gritted — grip belongs in the surface films only.
3. Pre-mixed products: stir before AND during application (a drill paddle at start, hand-stir each tray refill) — settled grit is the #1 uneven-texture cause. Roll in tight sections with a medium-pile roller, one wet pass then one light lay-off; over-rolling ploughs the grit into stripes.
4. Broadcast systems: roll the receiving coat in workable strips; scatter grit evenly onto the wet resin (to refusal for full-broadcast, or at datasheet g/m² for partial), by hand-cast or hopper; let cure; sweep/vacuum loose excess; lock with the seal coat rolled firmly so grit anchors without drowning.
5. Zone edges: mask grip zones to crisp lines — a straight painted edge between textures reads as design; a ragged one reads as spill.
6. Cure discipline: traffic times as for the base chemistry, and resist early sweeping of broadcast floors — grit not yet locked comes off in the broom.

The finishing test: walk it wet before handover (in the site's real footwear), and keep a labelled sample of the grit and product batch — future patch repairs match texture only if the recipe survives.

The two lifetime questions, answered by texture physics:

Cleaning: effort scales with grade — fine textures mop normally; medium wants deck-brush or rotary-brush washing (string mops snag and shred on proper grit); coarse cleans by brush, hose, or pressure — never mop. Universal rules: alkaline or neutral cleaners matched to the base resin, rinse thoroughly (trapped detergent film defeats texture exactly as on rated tiles), and schedule by contamination — a gritted kitchen lane needs nightly brushing, a gritted fire escape a seasonal wash. Design helps more than effort: specifying the minimum sufficient grade per zone (the grading FAQ) is the real cleaning strategy, and smooth coving/edges around textured fields keep the brush-work bounded.

Wear: grip degrades by three routes — aggregate polishing (cheap sand rounds off; aluminium oxide and quartz keep cutting edges for years — the buy-quality argument), film wear exposing then shedding grit in traffic lanes (visible as smoothing tracks — the recoat signal), and contamination glazing (grease and floor-polish films bridging intact texture — restored by deep cleaning, the first thing to try when 'the floor got slippery'). Lifespans at honest duty: additive-in-paint 1–3 years in traffic lanes; quality pre-mixed systems 3–5; anchored broadcast epoxy/PU 5–10+.

Managing it like a professional: walk-test wet quarterly (or pendulum-test where records matter), deep-clean before concluding wear, and renew by screen-and-regrit of lanes rather than whole floors — texture zones repair invisibly if the grit recipe was kept. A rated floor with that little management stays rated; the one 'installed and forgotten' quietly becomes the smooth floor it was bought to replace.

Grit is agnostic; the binder decides everything else. Match the base to substrate and duty exactly as if no grit were involved:

Epoxy-based anti-slip — the concrete workhorse: deepest bond to ground slabs, highest build to anchor coarse broadcast, best chemical resistance per price. Choose for workshops, ramps on concrete, wash bays, plant rooms. Its known limits ride along: UV ambering outdoors (top-coat or accept), rigidity on moving substrates. Polyurethane-based — the flexible, weatherproof tier: UV-stable aliphatic versions own external walkways, fire escapes, and metal stairs (flex over steel + no chalking), and PU's abrasion life keeps texture anchored longest in trafficked lanes. Premium price, thinner build per coat (grit sizing adjusts accordingly). Acrylic and one-pack deck paints — the accessible tier: pre-textured or additive-ready, brush-and-roll simple, adequate for domestic steps, porches, garden ramps, and light-duty refreshes. Shorter recoat cycles are the honest trade for the easy application; on real duty they are the maintenance-heavy choice. Specialist bases for their niches: moisture-tolerant epoxies on damp slabs, urethane-cement under thermal shock, GRP-embedded systems where sheet-format nosing/tread covers beat liquid application on worn steel stairs.

The composite rule: pick the binder for the floor's chemistry problem, the grit grade for its contaminant, and the format (pre-mixed / broadcast / sheet) for the installer's control needs — three independent choices that the phrase 'anti-slip paint' hides, and that a five-line specification makes explicit. The floors that stay safe for a decade were specified in those three lines; the ones repainted every spring were bought by the tin's front label.