For building materials and metal goods, the two variables that actually determine NMFC classification are material and density — within "metal products," aluminum, brass/bronze/copper, and zinc each have entirely different codes, and almost every metal code splits into several density tiers. Aluminum articles (NMFC 13120) and brass/bronze/copper articles (NMFC 30160) can, in theory, land anywhere across the full class 50 to 400 range depending on density. Confirm the material first, then the actual measured density — neither step can be skipped.
What to watch for when classifying building materials and metal
Material determines the code; density determines the class
Metal goods are split by material into separate code families — aluminum (13120), brass/bronze/copper (30160), zinc and zinc alloys (201050), and other metals or alloys (135955) are each independent and shouldn't be mixed up. Once you've identified the code for the material, confirm the sub-code and class from the actual measured density — not a "typical" density for that material — because the same metal's density varies a lot depending on form: bar, plate, castings, wire, or scrap.
The "miscellaneous" building-material code gets overused
Miscellaneous building or paving materials (NMFC 33785) is a broad code — covering waterproofing, skylights, thresholds, awnings, and more — density-tiered across the full class 50 to 400 range. If a product has a more specific dedicated code — brick/blocks/slabs/tile under NMFC 32275 (also density-tiered across the full range) or waterproofing/vapor-barrier sheeting under NMFC 175340 (a flat class 70) — use the dedicated code instead of defaulting to "miscellaneous" out of convenience — it's a common reason carriers reclassify a shipment on arrival.
Conduit and piping are split by specific use
Conduit, pipe, smokestacks, tubing, and fittings (non-clay/concrete, NMFC 50970), plumbers' goods (NMFC 158880), and highway guardrail cable supports (NMFC 95250) might all look like "metal piping" on the surface, but they're actually coded by specific end use. Describe the commodity by its actual application rather than a generic "metal piping" label.
Example building materials and metal NMFC codes
The codes below are verified against ShipMay's own NMFC database and are meant to illustrate classification logic — the exact code and class that applies to your shipment depends on your actual commodity description, measured density, and the carrier's own review:
| Commodity | NMFC Code | Typical Class Range |
|---|---|---|
| Aluminum articles (bars, plates, extrusions, fittings) | 13120 | 50 – 400 (13 density tiers) |
| Brass, bronze, or copper articles | 30160 | 50 – 400 (13 density tiers) |
| Zinc or zinc alloys | 201050 | 50 – 400 (13 density tiers) |
| Brick, building blocks, slabs, or tile | 32275 | 50 – 400 (13 density tiers) |
| Miscellaneous building or paving materials | 33785 | 50 – 400 (13 density tiers) |
| Vapor-barrier or waterproofing sheeting | 175340 | 70 |
How to find the code that actually applies to your shipment
For building materials and metal goods, break it down by material and application first: confirm the code family for the material — aluminum, copper, zinc, other alloys — then check the density sub-code by searching a specific commodity in the NMFC Lookup tool; use a dedicated code (brick, waterproofing sheeting, etc.) over "miscellaneous" whenever one exists; and describe pipe/plumbing items by actual use, not a generic "metal goods" label. When in doubt, send ShipMay the commodity, weight, and dimensions — the final code and class are still subject to the carrier's own review.
Common mistakes
- Filing all "metal products" under one code regardless of material — aluminum, copper, and zinc each have their own code family and shouldn't be combined.
- Defaulting to "miscellaneous building materials" for convenience — a dedicated code should be used whenever one exists; "miscellaneous" invites a carrier reclassification.
- Classifying by material alone, ignoring density — the same metal in different forms (bar, plate, castings, scrap) has very different densities and must be actually measured.
Related reading
- Free NMFC code lookup
- Freight class calculator
- LTL Reweigh and Reclass: Why Freight Bills Change After Pickup
- A complete guide to U.S. freight accessorial charges
- LTL freight quotes and multi-carrier rating
- Truckload shipping
NMFC code guides for other common commodity categories: electronics, furniture and glassware, food and packaging, auto parts.
Sources
- National Motor Freight Traffic Association (NMFTA), which develops and maintains the NMFC classification standard.
- The specific codes, descriptions, and class ranges listed above are verified against ShipMay's own NMFC database and are illustrative of classification logic only — they don't replace the carrier's own review at time of shipment.
