FRP Grating Selection Process
Seven Steps to the Right FRP Grating
Follow the steps in order. Each step feeds the next; never pick a colour or a surface before the structural and corrosion questions are settled.
1 · Environment Assessment
Identify chemicals (name, concentration, temperature), UV/sunlight exposure, humidity, and fire/smoke code. This drives the resin system and surface grade.
2 · Load Determination
Define uniform live load (kN/m² or psf) and any concentrated point loads (forklift wheel, equipment foot). Classify occupancy per your building code.
3 · Panel Type Choice
Molded for bi-directional strength and impact; pultruded for ~2× stiffness, long spans and heavy, uni-directional loads.
4 · Span Check
Orient pultruded bearing bars across the span. Confirm deflection limit (L/100–L/200) against certified load/span charts.
5 · Resin Selection
Isophthalic polyester as the workhorse; vinyl ester for aggressive chemistry; phenolic for fire/smoke; UV-stabilized for outdoor service.
6 · Surface Selection
Grit-top for wet/maximum traction; concave/convex standard; smooth for cleanroom and food contact. Match to slip-risk.
7 · Accessories Specified
Hold-down clips (SS304/316), screws, edge banding, cut-out reinforcement and handrail — specified with the panel, not added later.
1. Environment Assessment — Start with the Chemistry
The resin system is the single most important decision in FRP grating selection. Identify every chemical the grating will contact — name, concentration and temperature — before anything else. A panel chosen on load alone will fail in weeks if the resin cannot survive the chemistry.
| Environment Factor | What to Record | Why It Drives the Choice |
|---|---|---|
| Chemicals | Name, concentration, temperature, contact type (continuous C / splash S / infrequent I) | Sets the resin family: ZeAll ISO for general industrial, ZeAll VE for strong acids/oxidizers, ZeAll Super VE for severe duty |
| UV / sunlight | Outdoor service, direct sun hours | UV-stabilized grade required for outdoor panels to prevent surface degradation |
| Humidity / salt air | Coastal exposure, marine atmosphere | Corrosion grade and clip material (SS316 preferred) |
| Fire / smoke code | ASTM E84 flame-spread & smoke-developed limits; USCG / DNV for marine | ZeAll FR (spread ≤10) or ELS (low smoke) for enclosed/escape-route service |
| Temperature | Max continuous service temp (°F/°C) | ZeAll VE 180°F (82°C); ZeAll ISO/FDA/FR 150°F (66°C); never exceed the resin ceiling |
| Wash-down / hygiene | Food contact, cleanroom, barefoot areas | ZeAll FDA (USDA approvable) or smooth surface for cleanability |
Sources: resin temperature ceilings and fire ratings [FGRAT p.7, p.19]; chemical contact legend C/S/I/N [FGRAT p.19, §6].
2. Load Determination — Uniform, Concentrated & Impact
Define every load the grating must carry. FRP is stiffer than it is strong in the classic sense — deflection, not rupture, is usually the governing limit — so be precise about both the load value and the deflection criterion.
| Load Case | Typical Value | Notes |
|---|---|---|
| Pedestrian walkway (UDL) | 50–65 psf (2.4–3.1 kN/m²) | Baseline live load for most industrial platforms and walkways |
| Assembly / crowded area | 75–100 psf (3.6–4.8 kN/m²) | Check local building code for occupancy classification |
| Maintenance / equipment mat | As specified by owner | Uniform mat load over defined area — often 100 psf+ |
| Forklift wheel (concentrated) | Wheel load × impact factor | Check each wheel separately: a panel fine for UDL can deflect badly under one wheel |
| Equipment foot / point load | Actual foot load (kN/lbf) | State contact area; concentrated loads usually control pultruded bearing-bar size |
| Impact factor | ×1.25–2.0 on dynamic loads | Forklifts, vibrating equipment, dropped loads — apply before comparison to charts |
When in doubt, send the actual load list to ZeAllgrate engineering — we return the panel and the chart reference.
3. Panel Type — Molded or Pultruded?
Two different products, two different engineering personalities. Molded grating is built in a closed mold with a mat of glass — equal strength in both directions. Pultruded grating is drawn through a die with continuous roving — roughly twice the stiffness along the bearing bars, at ~70% glass by weight.
| Characteristic | ZeAllgrate Molded | ZeAll Pultruded |
|---|---|---|
| Glass content | ~33% by weight | ~70% by weight |
| Strength direction | Bi-directional (equal in both panel directions) | Uni-directional (strong along bearing bars) |
| Stiffness (E) | Moderate — shorter spans | ~2× stiffer — long spans, heavy unidirectional loads |
| Impact resistance | Excellent (closed mat construction) | Very good (roving-dominant) |
| Typical clear span | ≤ 1.2 m (4 ft) conservative | 1.2–2.5 m+ with correct bearing-bar series (I-6010 / I-6015) |
| Best for | Platforms, walkways, covers, general plant areas | Long-span walkways, trench covers, mezzanines, heavy point loads |
Sources: glass content and stiffness comparison per Industry reference molded & pultruded catalogs [FGRAT; DURA p.2].
4. Span Check — Deflection Is the Real Limit
Orient the bearing bars across the clear span — never parallel to it. Then confirm the deflection limit against certified load/span charts. FRP is checked on deflection, so a stricter limit (L/200 vs L/100) means a smaller allowable span for the same load.
| Deflection Limit | Meaning | Typical Use |
|---|---|---|
| L/100 | Deflection = 1/100 of clear span | General industrial walkways, less sensitive |
| L/150 | 1/150 of clear span | Standard pedestrian platforms, balconies |
| L/200 | 1/200 of clear span | Sensitive areas, machinery decks, high-crowd areas |
| 3/8 in (≈9.5 mm) absolute cap | Max absolute deflection regardless of span | OSHA / conservative practice for long spans |
Support width
Minimum 40 mm bearing on the support structure at each end — never less.
Clip spacing
Hold-down clips at support intersections, spacing ≤ 1219 mm (48 in); minimum 4 clips per panel.
Framing tolerance
Keep supports level within ±5 mm; uneven framing adds eccentric load.
Sources: deflection criteria and support practice [FGRAT §7; IndustrialInfoLoadTables].
5. Resin Selection — Match Chemistry to Service
ZeAllgrate produces 3+ resin families with 30+ custom formulations. The rule is simple: list your chemicals and temperatures, and the resin is matched by engineering — never pick a resin by price first.
| Resin System | Corrosion Grade | ASTM E84 | Max Temp | Best For |
|---|---|---|---|---|
| ZeAll ISO — improved isophthalic polyester | Very Good (general industrial) | ≤25; USCG general | 150°F (66°C) | Cost-effective workhorse: moisture, mild acids/alkalis, salts |
| ZeAll VE — vinyl ester | Excellent | ≤25; self-extinguishing | 180°F (82°C) | Strong acids, oxidizers, chlorides — general corrosive service |
| ZeAll Super VE — custom VE | Excellent (severe) | Non-FR unless specified | Up to 400°F (204°C) | Solvents, oxidizers, ClO₂, NaOCl, desiccants |
| ZeAll FR — extra fire-retardant VE | Excellent | ≤10 — lowest offered | 150°F (66°C) | Escape routes, transit, enclosed spaces |
| ELS — low-smoke modified polyester | Good (low-smoke priority) | Spread ≤25; smoke ≤100 | 150°F class | Smoke-sensitive enclosed spaces |
| ZeAll FDA — food-grade iso, antimicrobial | Very Good (food contact) | ≤25 | 150°F (66°C) | Food & beverage, washdown — USDA approvable |
Sources: resin list and ratings [FGRAT p.7, p.19, §5.3].
6. Surface Selection — Traction vs Cleanability
The surface is a safety decision. Match it to the slip risk and the hygiene requirement — a grit surface that is right for a wash-down chemical plant would be wrong in a cleanroom.
| Surface | Traction | Best For |
|---|---|---|
| Grit-top (silica-embedded) | Maximum slip resistance, wet/oily | Wash-down areas, ramps, offshore, any wet service |
| Concave | Good standard traction | General walkways, drainage platforms — the industry default |
| Convex | Good traction, smooth top | Barefoot / light-traffic areas where a flat top helps |
| Smooth | Lowest traction | Cleanroom, food contact, palletizing — where cleanability beats grip |
Rule of thumb: wet, oily or wash-down service → grit-top; hygienic or cleanroom → smooth; everything else → concave.
7. Accessories — Specified with the Panel, Never Added Later
Hold-down clips, edge banding, cut-out reinforcement and handrail must be specified in the same order as the panel — retro-fitting them on site costs more and voids the engineered detail.
Hold-down clips
SS304 standard; SS316 for marine / chloride service. Spacing ≤ 1219 mm (48 in), minimum 4 clips per panel, at support intersections.
Edge banding
FRP flat bar or resin-filled edges on cut panels — restores load capacity and prevents delamination at cut edges.
Cut-out reinforcement
Openings for pipes / equipment must be re-framed with bearing bars — never leave a raw cut-out in a load path.
Handrail & toeboard
FRP handrail systems bolt to the grating edge; toeboard required where fall-through or dropped-tool risk exists.
Expansion joints
FRP moves more than steel — leave designed gaps between panels and at perimeters per the thermal expansion guide.
Fasteners
SS304/316 bolts, washers and nuts; never carbon steel in corrosive service.
Engineer's Decision Tree
| Question | If YES → | If NO → |
|---|---|---|
| Aggressive chemistry (strong acid, oxidizer, ClO₂, solvent)? | Vinyl Ester resin | Isophthalic Polyester |
| Fire / smoke code demands low-flame, low-smoke? | Phenolic or Class A FR polyester | Standard FR resin |
| Outdoor / UV / salt-air exposure? | UV-stabilized grade | Standard grade |
| Clear span > 1.2 m OR heavy concentrated load? | Pultruded (I/T-bar, 70% glass) | Molded |
| Wet, oily or wash-down service? | Grit-top surface | Concave / convex |
| Cleanroom, food or barefoot area? | Smooth surface | Textured surface |
| Overhead / openings < 13 mm required? | Mini-Mesh (44% open) | Standard 38×38 mesh (70% open) |
Open Area Choice
Standard Mesh — 38.1 mm square
~70% open area, self-draining, light weight (e.g. 25.4 mm ≈ 12.7 kg/m²; 38.1 mm ≈ 18.6 kg/m²; 50.8 mm ≈ 19.5 kg/m²). Best for drainage and ventilation where foot-through-through hazard is not a concern.
Mini-Mesh — 12.7–19 mm opening
~44% open area, ~22.0 kg/m² at 38.1 mm. Prevents tools, small objects and high heels from falling through; required where overhead openings must meet OSHA/ISO fall-through limits.
Run the Selection with an Engineer
Share your chemicals, span, load and code — we return a panel, resin, surface and accessory list.
Source: ZeAllgrate (Fiberglass Grating Manufacturers Council / ACMA) design guidelines; ASTM International; ISO 14122; OSHA 29 CFR 1910. Indicative data for specification guidance only — final design verified by ZeAllgrate engineering against certified load/span charts.