To choose FRP grating, decide six things in this order: the resin for your environment, the grating type and depth for your span and load, the mesh, the surface, the fire requirement, and the panel size and colour. Working in this order avoids the most common mistake, which is picking a thickness first and then finding it fails on span or on chemicals. Each step below uses MACHS product data, so you can apply it directly.
Key Takeaways
- Start with the environment: it sets the resin system, which you cannot change after installation.
- Choose depth by span and deflection. Under 4.8 kN/m², 25 mm molded grating suits spans up to 610 mm, 38 mm up to 914 mm and 50 mm up to 1219 mm.
- Use mini mesh (19 × 19 or 20 × 20 mm, 42% open area) where small objects, heels or accessibility rules matter.
- Specify grit top for wet, oily or outdoor areas, and ask for the fire test report that matches your configuration.
1Which resin does the environment need?
Match the resin to the worst chemical exposure the grating will see:
- Heavy chemical corrosion (acids, alkalis, plating, mining): VCF vinyl ester.
- General industrial corrosion (water treatment, marine, power): IIF isophthalic.
- Food processing areas: IFF isophthalic food-grade system.
- Fire-critical areas (offshore, tunnels, enclosed spaces): PIN phenolic.
- Light corrosion or general building use: OAF or OAG orthophthalic.
List the chemicals, concentrations and temperatures, then read our FRP grating chemical resistance guide.
2Molded or pultruded, and how deep?
Measure the clear span between supports and define the load, then check deflection. Our test data under a uniform load of 4.8 kN/m² with a span/200 limit gives this starting point:
| Clear span | Suitable grating | Deflection at 4.8 kN/m² |
|---|---|---|
| up to 610 mm | 25 mm molded, 38 × 38 mesh | 2.11 mm |
| up to 914 mm | 38 mm molded, 38 × 38 mesh | 3.45 mm |
| up to 1219 mm | 50 mm molded, 50 × 50 mesh | 4.93 mm |
| longer spans or heavier loads | Pultruded, e.g. I4015 (38 mm) | 0.76 mm at 914 mm |
Molded grating has equal strength in both directions and is easiest to cut on site. Pultruded grating is much stiffer along its load bars. The detailed comparison is in molded vs pultruded FRP grating, and the method is in how to calculate FRP grating load capacity.
3Which mesh size fits the use?
- 38 × 38 mm square mesh (68% open): the standard for industrial walkways and platforms. Good drainage.
- 50 × 50 mm square mesh (71% open): used with 50 mm grating for longer spans.
- 19 × 19 or 20 × 20 mm mini mesh (42% open): stops small tools and debris, and suits pedestrian areas. The 2010 ADA Standards limit openings in accessible floor surfaces so that a 1/2 in (13 mm) sphere cannot pass.
- Rectangular meshes (for example 25 × 100 or 38 × 152 mm): stronger in one direction. Used for narrow walkways and stair treads.
4Standard top or grit top?
Use grit top for outdoor, wet, oily or icy areas. The standard top is easier to clean and suits dry indoor areas. On pultruded grating, I-bar panels come with grit or grooved tops, and T-bar panels with grit tops. Where liquids or small parts must not pass through, specify covered grating with a smooth or gritted plate.
5What fire performance does the project require?
Find the fire standard in your specification first. For surface burning, our SGS tests to ASTM E84 gave Class A results on 38 mm molded grit-top grating (flame spread index 10–15) and on 38 mm I-6015 pultruded grating (flame spread index 10). A report applies only to the configuration tested, so ask for the report that matches your thickness, resin and surface. For offshore escape routes, see our guide to fire-rated grating offshore.
6Which panel size and colour?
Choose the standard panel that wastes least when cut to your layout: 1220 × 4000, 1220 × 3660, 1220 × 2440 or 915 × 3050 mm for most molded grating, and 1524 mm wide panels for 38 mm. Standard colours are RAL 1003 signal yellow, 6010 grass green, 7004 signal grey, 7015 slate grey and 7035 light grey. Yellow is common for edges and steps, and grey for general floors.
What does a finished specification look like?
A complete specification line answers all six steps. For example:
Each term is explained in FRP grating specifications explained. Sending a line like this, with your layout drawing, gets you comparable quotes. Our RFQ checklist lists the other details buyers usually add.
Which selection mistakes are most common?
- Choosing thickness before measuring the span. Deflection grows quickly with span. In our tests, going from 610 to 914 mm raised 38 mm grating deflection from 0.81 to 3.45 mm under the same load.
- Using a general-purpose resin in a chemical area. See why FRP grating installations fail.
- Turning rectangular or pultruded panels the wrong way. The load-bearing direction must span between supports.
- Assuming one fire report covers every product.
Send us your span, load, chemicals and fire standard. We return a recommended grating type, depth, resin and surface with the quotation.
See the FRP grating range →Frequently Asked Questions
What is the most common FRP grating specification?
For industrial walkways, 38 mm molded grating with 38 × 38 mm mesh is the most common. It weighs 19.50 kg/m² and, in our tests, deflected 3.45 mm at a 914 mm span under 4.8 kN/m².
Can one grating type be used across a whole plant?
It can simplify ordering, but it is not always economical. Chemical areas may need vinyl ester, while general walkways can use a lower-cost resin. Splitting the order by area often saves money.
Do I need an engineer to approve the selection?
For structural platforms and public areas, yes. Our data is a starting point. The project engineer confirms loads, deflection limits and the applicable standard, such as AS 1657 in Australia.
