Covers (grates and slots)

The channel cover is the visible and accessible element of a linear drainage system. It must be suitable for the load class of the channel and be traffic-safe. According to EN 1433 (formerly DIN 19580), the same load classes A 15 to F 900 apply to the covers as to the channel bodies. Additionally, the standard EN 124 applies, which regulates general requirements for copings and covers (especially dimensions of openings, insertion depth, and breaking load). For example, EN 124 requires a minimum overlap (insertion depth) of 50 mm in the frame for covers of classes D 400–F 900; for channel grates, this is often achieved through appropriately designed frames. If covers are secured in another way (e.g., bolted), the 50 mm rule can be waived as long as traffic safety is guaranteed.

The most common channel grates are made of cast iron (ductile iron), steel (usually galvanized, sometimes stainless steel), or plastic. Cast iron grates are very robust and durable and are primarily used from load class D 400 (road traffic) upwards. For lighter loads (load classes A15 – C250), steel and plastic grates are also popular because they are lighter and less expensive. Aluminum grates are occasionally found in design-oriented areas (courtyards, pools); they are lightweight and corrosion-free, but only suitable for pedestrian traffic. Regardless of the material, all covers must meet the standard requirements (strength, gap width, etc.) and be tested accordingly. The class and manufacturer are usually stamped on the grates (marking according to EN 1433 or EN 124).

Gutter covers are available in various designs, adapted to their intended use. Bar gratings: Classic gratings with bars running perpendicular to the direction of travel. They offer high load-bearing capacity and a large inlet cross-section (typical in road applications from load class D 400 upwards). Longitudinal bar gratings: Here, the load-bearing bars run lengthwise, visually appealing in pedestrian zones as they resemble paving joints. Mesh gratings: Grids made of crossed bars (rectangular openings). Often used for driveway entrances. Slotted covers: Covers without a visible grating – only a narrow slot (often 1–3 cm wide) along the channel. There are also special designs, e.g., for highways or sports fields. For highways, for example, monolithic channels (channel body and cover are a single component) are used. These can also have lateral inlet openings for the use of porous asphalt.

The cover significantly influences how quickly water can enter the gutter. Therefore, minimum opening areas are specified. Generally, the combined free cross-sectional area of all openings should be at least 30% of the gutter's clear opening. If the cover is too dense, there is a risk of surface water pooling. The arrangement and size of the slots/openings also depend on accessibility (safety for steps, no excessively large gaps) and susceptibility to debris (leaf trapping). Compromises must be made here: A fine-mesh grate retains leaves but allows less water to pass through. Therefore, in cases of heavy rainfall or significant leaf fall, cleaning intervals may need to be shortened or special leaf trap inserts used.

Especially in public areas, gutter covers must be secured against being lifted out and rattling. Previously, grates were often fixed with screws (standard grate securing). Today, tool-free quick-release fasteners are becoming increasingly common, simplifying maintenance. Examples include click-lock systems, toggle screws, or spring-loaded clips that lock the grate into the frame. It is crucial that, from class C 250 upwards, a traffic-safe locking mechanism is in place – an unsecured grate could otherwise be shaken by traffic and lifted out. Modern locking systems consist, for example, of a stainless spring steel bar attached to the grate that engages in recesses in the gutter frame. These allow for quick opening with a special lever tool, without loosening screws. However, in sensitive areas (high risk of theft), screwed-on covers are sometimes still used. Another aspect is noise reduction: modern locking mechanisms prevent the grate from rattling when vehicles drive over it, for example, through the use of plastic pads or tight springs.

The choice of the right cover depends on load, aesthetics, and function. A narrow slot might be preferable in pedestrian zones, while a robust grating is needed in high-traffic areas. It is always important that the grating and channel body function as a system and are tested together.