FRP Guides

FRP Grating Surface Options: Concave, Grit-Top and Covered Explained

In short: FRP grating is supplied with three main top surfaces. A concave (meniscus) surface has slightly dished bar tops that give built-in slip resistance and are easy to clean. A grit-top surface has bonded silica or aluminum oxide grit for higher slip resistance in oily, wet, sloped or icy areas. A covered (solid-top) surface bonds a gritted plate on top to create a continuous floor where nothing may fall through. Choose based on contamination, cleaning method, footwear, slope and whether small objects must be contained.

FRP Grating Surface Options: Concave, Grit-Top and Covered Explained – In short summary: key points at a glance

Table: Comparison – FRP Grating Surface Options — Comparison. Summary diagram of the table in this guide.

Why the surface matters

Slips are among the most common workplace injuries, and walkway surfaces in processing plants are often wet, oily or chemically contaminated. FRP grating can provide slip resistance without the coatings that steel grating may need, and the finish is molded or bonded into the product. The surface also affects cleaning, comfort and drainage.

Diagram: Slip testing and standards – FRP Grating Surface Options — Slip testing and standards: summary diagram from this guide.

Concave (meniscus) surface

During molding, the top of each bar forms a slight concave curve. The edges of the curve provide grip, and the smooth surface is easy to clean.

Best for: general industrial walkways, wet areas without heavy oil, and food or wash-down areas where grit could trap residue.

Considerations: less slip resistance than grit-top in oily or icy conditions.

Grit-top surface

Quartz/silica sand or aluminum oxide grit is bonded into the top surface during or after molding. Grit size can be selected: finer grit is more comfortable and easier to clean, while coarser grit gives more traction.

Best for: oily or greasy areas, ramps and slopes, outdoor platforms exposed to rain or ice, offshore decks and stair treads.

Considerations: harder to clean, can trap residue, and may wear in very high-traffic zones over many years. Aluminum oxide is harder than silica and generally more wear resistant.

Covered (solid-top) grating

A solid FRP plate, usually with a gritted surface, is bonded to the top of the grating. The result is a continuous floor while keeping the grating's strength beneath.

Best for: areas where tools, bolts or small parts must not fall through; under-floor areas with people working below; areas needing wheelchair or trolley access; and odor or spray containment over channels.

Considerations: no drainage through the panel, more weight, and liquids must be drained across the surface. Load tables differ from open grating.

Diagram: Choosing the right surface – FRP Grating Surface Options — Choosing the right surface: summary diagram from this guide.

Comparison

Factor	Concave	Grit-top	Covered
Slip resistance	Good	Highest	High (gritted plate)
Cleaning	Easiest	Harder	Moderate
Drainage	Through mesh	Through mesh	Across surface only
Small objects	Pass through	Pass through	Contained
Comfort / heels	Good	Good (fine grit)	Best
Typical use	General walkways	Oil, slopes, ice	Containment, access floors

Slip testing and standards

Slip resistance is measured in different ways in different regions:

Pendulum test (for example BS 7976 in the UK, and EN 16165 in Europe), giving a Pendulum Test Value (PTV)
Ramp test (DIN 51130), giving R-ratings from R9 to R13
Tribometer tests such as ANSI A326.3 in the US (wet dynamic coefficient of friction)

A slip rating belongs to the specific surface tested. If your specification requires a rating, state the standard and the target value, and ask for the test report for the exact product and surface.

Choosing the right surface

What contaminants are present? Oil and grease point to grit-top.
How is the area cleaned? Frequent wash-down with food residue favors concave.
Is it sloped, outdoors or icy? Grit-top.
Must small objects be contained, or is the area above people? Covered.
Is wheeled access or accessibility required? Covered or small mesh. See FRP Grating Mesh Sizes.

For stairs, use grit-top treads or GRP stair nosings. See FRP Stair Treads vs Nosings vs Tread Covers.

Color and visibility

Surface and color work together. Yellow is often used for safety walkways and edges, while gray and green are common general colors. See FRP Grating Colors.

Customization

FIBROVX supplies FRP molded grating and pultruded grating with concave, grit-top or covered surfaces. We can adjust grit type and size, cover plate thickness and color, and supply matching stair treads and tread covers. Tell us the environment and any slip-test requirement.

Need a quote or a drawing check?

FIBROVX manufactures FRP products in our own factory in China and builds every item to order: sizes, resin system, color, molds and OEM branding. Send your application, dimensions or drawing, quantity and destination port.

Request a Quote

Common mistakes with grating surfaces

Specifying grit everywhere. Grit-top surfaces give more grip but are harder to clean and can be uncomfortable for kneeling work. Use them where contamination makes it necessary.
Assuming covered grating drains. A covered top is solid, so liquids run across it rather than through it. Plan the fall and drainage.
Ignoring wear. Heavy foot or cart traffic gradually wears any surface. Check the surface regularly in high-traffic routes.
Relying on a generic slip rating. Slip resistance depends on the specific product, the contaminant and the test method. Ask for test data for the exact surface.

Key terms

Meniscus (concave) surface: A slightly concave top on each bar, formed in the mold, which gives grip without added grit.
Grit: Hard aggregate, such as quartz sand, bonded to the top surface with resin to increase slip resistance.
Covered grating: Grating with a solid FRP plate bonded on top, giving a continuous surface without openings.
Slip resistance: How well a surface resists slipping, measured by standardized tests. Results depend on the test method and contaminants.
Open area: The percentage of the panel surface that is open, which affects drainage and weight.

FAQ

Which FRP grating surface is the most slip resistant?

Grit-top generally gives the highest slip resistance, especially with oil or water contamination. Confirm with a test report if your specification requires a rating.

Does grit wear off?

Bonded grit is durable, but very heavy traffic over many years can wear it. Aluminum oxide grit is more wear resistant than silica.

Is concave grating slip resistant?

Yes, for many wet environments. In oily or icy areas, grit-top is usually preferred.

Can covered grating carry the same load?

Covered grating has its own load tables. The cover plate adds stiffness, but you should check the specific table.

Can I add grit to existing grating?

Grit-top surfaces are normally applied in the factory with resin. Field-applied grit kits and anti-slip coatings exist, but their bond and durability depend on surface preparation and the product used; factory-applied grit generally lasts longer.

Which surface is best for oily areas?

Grit-top surfaces generally give the most grip where oil or grease is present. Confirm with slip test data for the specific product and contaminant.

Related guides

Sources

A US FRP grating manufacturer, "FRP Molded Grating Details and Options" (meniscus, grit and covered tops)
UK HSE, "Assessing the slip resistance of flooring" (pendulum test, PTV): https://www.hse.gov.uk/pubns/geis2.pdf
ANSI A326.3 overview, Tile Council of North America (wet DCOF): https://tcnatile.com/resource-center/dynamic-coefficient-of-friction/