Code Update: Designing and Specifying Fabricated Metal Access Hatches with ASTM C1802

Fabricated metal access hatches are essential yet easily overlooked components in modern construction. Designed to remain unobtrusive, they provide secure access to utilities, mechanical systems and maintenance areas while blending seamlessly into floors, sidewalks, roadways or other surfaces. Their primary function is practical, allowing personnel to access otherwise hidden systems, but they also enhance safety, durability and the aesthetic integration of infrastructure.

Although these hatches sit “out of sight,” their engineering is critical. They must bear pedestrian, vehicle or even aircraft loads safely through time. A poorly specified hatch can lead to premature wear, malfunction, structural failure or unsafe conditions, highlighting the importance of standards such as ASTM C1802 for architects, engineers and contractors.

Proper Specification

In practice, fabricated metal access hatches are sometimes specified too generically. A project may simply call for “traffic loading” or reference AASHTO HS20 loading without any further detail. This approach overlooks critical project-specific needs, including precise load requirements, environmental exposure and installation constraints.

In past instances, improper specification has led to installations that are functional but only marginally serviceable. In one instance, a series of communication vaults located underneath the driveway to a busy parking lot was installed with “HS20” hatches. The hatches ably withstood the daily repeated impacts from vehicle wheels but deflected noticeably during their first year of service because they were designed for static or nearly static wheel loads as opposed to dynamic traffic loads. The hatches are routinely inspected and have continued to function adequately, so replacement hasn’t been necessary, but the unsightly permanent deflections clearly weren’t intended by the specifier.

Each hatch must be specifically designed for its anticipated loading scenario. Pedestrian walkways, roadways and airport aprons all impose different stresses, and hatches must safely accommodate these conditions. ASTM C1802 addresses this by defining 10 distinct load classes, providing a clear framework to specify hatches that match the structural demands of the installation environment. Correct application of these classes ensures hatches are neither over-designed nor under-designed, improving safety and service life.

 

 

Introduction to ASTM C1802

ASTM C1802, “Standard Specification for Horizontal, Fabricated Metal Access Hatches,” establishes guidelines for the design, fabrication, testing and installation of horizontal access hatches. Its scope includes hatches installed in floors, sidewalks, roadways and other flat surfaces, addressing both structural and operational performance requirements.

Central to ASTM C1802 is the classification of hatches by load capacity. The standard defines 10 load classes, organized by intended use:

Some additional ASTM C1802 requirements include the following:

• Fabrication tolerances and material specifications to ensure durability.

• Hinges, locking mechanisms and seals for reliable operation and safety.

• Testing procedures to verify structural performance under expected loads.

Notice that Load Levels 4 though 7 are all designed to withstand 16,000-pound wheel loads in accordance with AASHTO specifications, but selection of the proper load level rating depends on the application or where the hatch will be located relative to traffic.

Matching ASTM C1802 Load Classes to Project Requirements

Specifying an access hatch involves more than referencing common traffic standards such as “HS20” or “HL-93.” These alone may not fully reflect the actual loads, especially dynamic effects or localized impacts. ASTM C1802 provides a structured approach to align a hatch’s design with the project’s true service conditions.

For instance, a hatch in a sidewalk outside a commercial building may require Load Level 1 or 2 for pedestrian loading. A hatch in a roadway carrying delivery trucks would need Load Level 5 or 6 for traffic loading. Airport installations demand careful selection of Load Level 8 or 9, depending on aircraft type and traffic patterns.

In the aforementioned parking-lot scenario, a hatch with a Load Level of 4 was most likely provided for the project. According to ASTM C1802, hatches with a Load Level of 4 are allowed to deflect up to 1/250th of the opening width and are restricted to parking spaces and areas within proximity of roadways. This is entirely appropriate for parking spaces or within medians and esplanades, but more appropriate for installation in the driveway would have been a Load Level 5 hatch with a deflection limit of 1/300th the width of the opening, which is allowed to be placed in parking lanes and alleyways where traffic speeds are limited to 15 mph.

If the hatch were to be in the main roadway outside the parking lot, a hatch with a Load Level of 7 would be required, with deflection limited to 1/800th the span and designed for full traffic moving at speed, including heavily loaded trucks.

Engineers should evaluate static and dynamic load scenarios, environmental exposure and installation constraints before selecting the appropriate ASTM C1802 class. This ensures safe, reliable and long-lasting hatch performance while avoiding unnecessary material and cost overdesign.

Conclusion

Fabricated metal access hatches may lie quietly beneath our feet, but their role in structural safety and functionality is crucial. Proper design and specification, guided by ASTM C1802, ensures hatches meet the unique demands of their environment, whether that’s a pedestrian walkway, a heavily traveled roadway or areas experiencing more extreme loads such as airports and cargo ports. The 10 Load Levels provided in ASTM C1802 simplify selection, allowing designers to accurately match the hatch’s capacity to project-specific needs. By adhering to ASTM C1802, engineers and architects can achieve durable, safe and unobtrusive access solutions that protect the facility and its users over the long term.

Code Update Hugh Martin