"H-20" is on almost every casting line in a municipal tender, but it gets used two ways, and catalog words like "heavy duty" have no single definition. Here's what each rating means, how AASHTO ratings compare to EN 124, and how to pick one by location. DomCast Metals is a Canadian-owned supplier of municipal castings; the rating of any SKU is confirmed per SKU at quote.
What H-20 and HS-20 mean
H-20 and HS-20 come from AASHTO bridge design criteria, not from a casting standard. They describe a design truck with a 32,000 lb axle, a 16,000 lb wheel load. The "S" in HS-20 adds a semi-trailer for bridge span calculations; a casting still sees the 16,000 lb wheel, so catalogs treat the two as the same rating. On its own, "H-20 rated" only says the casting was designed around a 16,000 lb wheel, not how it was tested or with how much margin.
Design wheel load vs. proof load
AASHTO M306, the casting standard, applies a 2.5 safety factor to the H-20 wheel: 2.5 x 16,000 lb = 40,000 lb. That's the proof load. It's applied through a 9" x 9" pad at the centre of the cover or grate, and the casting is then inspected for cracks or permanent deformation.
- Design wheel load (16,000 lb): the traffic the casting is meant to carry in service.
- Proof load (40,000 lb): the test load the finished casting must survive.
Some suppliers say "H-20" meaning the 16,000 lb design load with no proof test behind it. If you want the tested version, write "AASHTO M306, 40,000 lb proof load" rather than "H-20" alone. The AASHTO M306 guide covers the test and sample tender wording.
H-25
H-25 raises the design wheel load to 20,000 lb, and the same 2.5 factor gives a 50,000 lb proof load. Specify it where the road authority calls for H-25 traffic.
| Rating | Design wheel load | Proof load (2.5x) | Test pad |
|---|---|---|---|
| H-20 / HS-20 | 16,000 lb | 40,000 lb | 9" x 9" |
| H-25 | 20,000 lb | 50,000 lb | 9" x 9" |
What "light duty", "medium duty" and "heavy duty" mean
These are catalog terms, not standard designations. No AASHTO or ASTM document defines them, so two catalogs can put different numbers behind the same word. These tiers are what the National Precast Concrete Association publishes as common industry usage:
| Catalog term (industry usage) | Typical load range | Where it's used |
|---|---|---|
| Non-traffic | 0 to 2,500 lb | Landscape, areas closed to vehicles |
| Light duty | 2,500 to 16,000 lb | Sidewalks, terraces, landscape, golf carts, mowers |
| Medium duty | 16,000 to 40,000 lb | Between light duty and the M306 proof load; ask which number the catalog means |
| Heavy duty / traffic-rated | 40,000 to 100,000 lb | Streets and highways (M306 proof load and up) |
| Extra heavy duty / airport-rated | 100,000 to 200,000 lb and up | Aircraft pavements, port terminals |
One caution: an older US federal spec (GSA RR-F-621) called a casting "heavy duty" at a 25,000 lb centre load on a 9" x 9" pad, well short of M306, so "heavy duty" in a legacy catalog may not mean M306. Ask for the number, whether it's design or proof load, and the test data.
EN 124 classes for comparison
Tenders that borrow from European or international specs use EN 124:2015, "Gully tops and manhole tops for vehicular and pedestrian areas". It rates covers by test load in kilonewtons, tied to an installation location. The pound figures are unit conversions only; EN 124 and M306 use different test geometry and acceptance criteria.
| EN 124 class | Test load | Approx. lbf | Installation location per EN 124 |
|---|---|---|---|
| A15 | 15 kN | 3,400 | Pedestrian areas with no vehicle access |
| B125 | 125 kN | 28,100 | Footways, car parks, areas with occasional vehicle access |
| C250 | 250 kN | 56,200 | Kerbside channels, car parks, forecourts, slow-moving traffic areas |
| D400 | 400 kN | 89,900 | Road carriageways, hard shoulders, parking areas |
| E600 | 600 kN | 134,900 | Areas with high wheel loads (loading areas, docks, aircraft pavements) |
| F900 | 900 kN | 202,300 | Areas with very high wheel loads (aircraft pavements) |
D400 is the rough counterpart to H-20 or H-25 with an M306 proof load; E600 and F900 sit in the airport and port range. Don't write "D400 or H-20" as if they're interchangeable. Pick the system your road authority uses and keep it through the casting schedule.
Airport and port ratings
FAA guidance calls for castings that take a 100,000 lb wheel load at 250 psi tire pressure. Airport-rated castings are proof-loaded to 100,000 lb minimum and often 200,000 lb or more, and covers and grates are bolted to the frame, which FAA Advisory Circular 150/5370-10 calls for. Port terminals with container handlers fall in the same range. These are specified from the facility's own standards, not a municipal OPSD drawing. Flag them at quote.
Picking a rating by location
The rating follows the worst vehicle that can reach the casting, not the typical one.
- Sidewalk, boulevard, park path. Light duty is common, but check whether your municipal standard wants a traffic rating anywhere a vehicle can mount the curb before downgrading. DF220 is DomCast's light duty catch basin frame and cover.
- Parking lots, laneways. Medium duty at minimum; H-20 with an M306 proof load if garbage trucks or fire apparatus can enter.
- Local and collector roads. H-20 / 40,000 lb proof load. In Ontario the standard drawings for these locations are OPSD 401.010 (cast iron square frame with circular closed or open cover for maintenance holes) and OPSD 400.010 / 400.020 (cast iron square frames with dished or flat herringbone grates for catch basins). The drawing fixes the pattern and dimensions; the load rating comes from your municipal spec. DomCast's 401.010 and 400.010 are the SKUs for those drawings, rating confirmed at quote.
- Truck routes, arterials, industrial, port access. H-25 / 50,000 lb proof load where the road authority calls for it.
- Airports and container terminals. Airport-rated, bolted, per the facility's spec.
Order frame and cover as a matched pair at the same rating. Browse manhole covers, catch basin frames and grates, grates and drain covers, and valve boxes, then send the casting schedule with your quote request so load ratings and test documentation can be confirmed per SKU.
Frequently asked questions
Is HS-20 stronger than H-20?
Not for a casting. Both use a 32,000 lb axle and 16,000 lb wheel load; HS-20 only adds a semi-trailer for bridge span analysis.
What's the difference between an H-20 design load and an H-20 proof load?
Design load is the 16,000 lb wheel the casting carries in service. Proof load is the 40,000 lb test load AASHTO M306 requires (2.5 times the wheel load). A casting can be called "H-20" on design load alone, so specify "AASHTO M306, 40,000 lb proof load" if you want the tested version.
Does "heavy duty" mean H-20?
Usually, but not always. "Heavy duty" has no standard definition. Industry reference guides use it for castings at or above the 40,000 lb M306 proof load, but an older US federal spec used it for a 25,000 lb load. Ask for the number.
Which EN 124 class matches H-20?
D400 (400 kN, about 89,900 lbf) is the class for road carriageways and the nearest counterpart to H-20 / H-25 with an M306 proof load. The two systems test differently, so treat it as a comparison, not an equivalence.
Are DomCast castings rated to H-20 or H-25?
Confirmed per SKU at quote. Send the casting schedule with the rating and standard your tender names, and DomCast will confirm which SKUs meet it and what test documentation is available.
Sources: https://precast.org/blog/manhole-frame-and-cover-load-bearing-definitions/ · https://precast.org/wp-content/uploads/100323_Products_ManholeCastingReferenceGuide.pdf · https://municipalcastings.org/resources-articles/aashto-standards/ · https://www.trumbull-mfg.com/resources/did-you-know/meaning-of-h-20/ · https://www.jdpipes.co.uk/knowledge/manhole-covers/bsen124-explained.html · https://www.uxbridge.ca/public/download/files/311296 · https://www.toronto.ca/wp-content/uploads/2017/11/977b-ecs-specs-piperevs-Revision_Sheet_6_sw.pdf · https://sweets.construction.com/swts_content_files/2599/268171.pdf