Drainage Grates& Covers

Load ratings follow AASHTO (American Association of State Highway Transportation Officials) standards: Light Duty handles pedestrian traffic only. Class A supports passenger vehicles (up to 2,500 lbs per wheel). Class B handles light trucks (up to 5,000 lbs per wheel). Class C supports commercial vehicles (up to 10,000 lbs per wheel). Class D handles heavy trucks (up to 16,000 lbs per wheel). Class E/F supports airport and port equipment. Always select a rating that exceeds your actual traffic loads.

Cast iron (gray iron) is more brittle and prone to cracking under impact but is less expensive and adequate for lighter loads. Ductile iron contains nodular graphite that makes it more flexible, impact-resistant, and able to deform without fracturing. Ductile iron has 2-3x the tensile strength of gray iron and is required for heavy-traffic applications. For Class C and above load ratings, ductile iron is strongly recommended.

Stainless steel grates are essential in corrosive environments: food processing facilities, commercial kitchens, breweries, pools, coastal areas, and anywhere exposed to chemicals or salt. They also provide a premium appearance for visible installations. The higher upfront cost is offset by dramatically longer service life—stainless won't rust, corrode, or require replacement like carbon steel or iron grates in harsh conditions.

ADA (Americans with Disabilities Act) compliance requires openings that prevent cane tips, crutches, and wheelchair wheels from catching. For parallel-to-traffic installations, openings must be no greater than 1/2" wide. For perpendicular installations, openings can be up to 3/4" wide. Elongated openings must be oriented perpendicular to the dominant direction of travel. Heel-proof designs with small perforations or narrow slots typically meet these requirements.

Measure the inside dimensions of the frame or basin opening—this is the seated grate size. Common sizes include 6", 9", 12", 18", and 24" for catch basins, and standard widths for trench drains. Also measure frame depth if replacing both frame and grate. When possible, identify the manufacturer and model number of your existing system, as grates are designed to fit specific frames and may not be interchangeable between brands.

Open area percentage determines water intake capacity: Slotted grates (60-70% open) provide maximum intake but may not be heel-safe. Perforated grates (40-50% open) balance intake with heel safety. Bar grates offer high structural strength with moderate intake. Lattice/grid patterns combine aesthetics with functional drainage. For high-flow applications, specify grates with the highest open area that still meets your load and safety requirements.

Locking grates are recommended or required for: public areas where theft or tampering is a concern, safety-critical locations like playgrounds or schools, traffic areas where vibration could dislodge grates, and anywhere unauthorized access to the drainage system must be prevented. Locking mechanisms include bolt-down hardware, hinged frames with locks, and specialty tamper-resistant fasteners.

Tree grates are decorative grates installed around the base of trees in urban environments. They protect tree roots from foot traffic and compaction, allow water and air to reach the root zone, provide a stable walking surface, and enhance streetscape aesthetics. Tree grates come in various patterns (concentric rings, radial designs, custom logos) and can include expandable centers to accommodate tree growth.

Grate rattle occurs when grates aren't properly seated in frames. Solutions include: using rubber gaskets or neoprene strips between grate and frame, ensuring frames are installed level and true, selecting grates designed with noise-reducing features (machined bearing surfaces, tight tolerances), using bolt-down or wedge-lock systems to secure grates, and specifying solid-top frames where high traffic is expected.

Many decorative grate patterns are available in load-rated versions suitable for vehicle traffic. However, intricate patterns may have lower structural strength than simple bar or slot designs. When specifying decorative grates for traffic areas, always verify the load rating meets your requirements. For heavy-duty applications, consider using decorative patterns only in pedestrian areas and functional designs in drive lanes.