NAICS 423310

Overview

The North American Industry Classification System (NAICS) is the OMB-sponsored standard for categorizing U.S. business establishments so federal statistical agencies can collect, analyze, and publish economic data. NAICS replaced the SIC system in 1997 and was developed jointly by the U.S. Economic Classification Policy Committee, Statistics Canada, and Mexico’s INEGI to enable comparability across North America; the latest vintage is 2022. ¹
NAICS 423310 designates merchant wholesalers of lumber, plywood, millwork, and wood panels. The title and placement reflect Sector 42 (Wholesale Trade) and are used across Census programs and derivative federal statistics to organize activity for this segment. ²

See also on G2X:

• G2X — NAICS 423310 overview
• G2X — NAICS 423320 overview
• G2X — NAICS 423330 overview

What this NAICS covers

• Merchant wholesaling of lumber. ⁵
• Merchant wholesaling of plywood. ⁵
• Merchant wholesaling of reconstituted wood fiber products and wood panels. ⁵
• Merchant wholesaling of millwork, including doors, windows, and frames (all materials). ⁵
• Merchant wholesaling of wood roofing and wood siding. ⁵
• Merchant wholesaling of wood fencing. ⁵

Related NAICS and PSC codes

Exclusions and borderline cases

• Manufacturing activities are not classified under NAICS 423310. Sawmills belong in NAICS 321113. ⁶
• Manufacturing millwork (e.g., stairwork, moldings) is classified in NAICS 321918, not in wholesale trade. ⁶
• Sector 42 wholesalers may render services incidental to sales; however, stand‑alone installation or construction services fall outside wholesale trade. ⁷

Small business size standards and NAICS assignment

• SBA assigns small business size standards by NAICS; contracting officers must designate a NAICS code for each contract under 13 CFR 121.402. ⁸
• The current size standard for NAICS codes is maintained in SBA’s Table of Size Standards; refer to the table for NAICS 423310. ⁹

Frequently asked questions

• What does NAICS 423310 include?
  NAICS 423310 covers merchant wholesalers of lumber, plywood, reconstituted wood fiber products, wood panels, and millwork (including doors, windows, and frames). It also encompasses wholesaling of wood roofing, wood siding, and wood fencing. These are distribution activities, not manufacturing or construction services. ⁵

• How does 423310 differ from 423320 and 423330?
  423320 focuses on brick, stone, and related construction materials, while 423330 centers on roofing, siding, and insulation (generally nonwood). 423310 is specific to lumber/wood products and millwork. Selecting among them depends on the predominant commodity line sold. ³

• Which PSCs commonly align with wood construction material buys?
  PSC 5510 (Lumber & Related Wood Materials), PSC 5520 (Millwork), and PSC 5530 (Plywood and Veneer) are commonly used. Agencies should match the PSC to the dominant deliverable when ordering under NAICS 423310. ⁴

• Are services like installation included under 423310?
  Wholesale establishments may provide services incidental to the sale of merchandise (e.g., delivery, minor assembly). Stand‑alone installation, construction, or remodeling services are outside Sector 42 and should be coded under the appropriate construction or service NAICS rather than a wholesale trade code. ⁷

• What is the small business size standard for 423310?
  SBA maintains official size standards by NAICS in the Table of Size Standards. The applicable threshold may be in employees or receipts and can change through rulemaking. Always consult the current table to determine eligibility for offers and set‑asides referencing this code. ⁹

Useful resources

• Census: Classifying Businesses (NAICS background and adoption). ¹
• 2022 Economic Census — Sector 42 (Wholesale Trade) data tables and materials. ²
• SBA: Small business size standards (overview and regulatory links). ⁸
• Acquisition.gov: Product and Service Codes (PSC) Manual (April 2025). ⁴

References

1. U.S. Census Bureau — Classifying Businesses (NAICS adoption and development), 1997 adoption overview. https://www.census.gov/about/history/historical-censuses-and-surveys/census-programs-surveys/economic/classifying-businesses.html
2. U.S. Census Bureau — 2022 NAICS Sector 42: Wholesale Trade (Economic Census resources). https://www.census.gov/data/tables/2022/econ/economic-census/naics-sector-42.html
3. U.S. Census Bureau — Employer Categories and Corresponding Establishment NAICS Industries (lists 423310/423320/423330 within Sector 42). https://www.census.gov/programs-surveys/esp/guidance/employer.html
4. Acquisition.gov — Product and Service Codes (PSC) Manual, April 2025 (definitions for 5510/5520/5530). https://www.acquisition.gov/sites/default/files/manual/PSC%20Manual%20April%202025.pdf
5. U.S. Census Bureau — 1997 NAICS Sector 42 archives (industry description for 421310 Lumber, Plywood, Millwork, and Wood Panel Wholesalers). https://www.census.gov/naics/resources/archives/sect42.html
6. U.S. Census Bureau — Manufacturing sector references (321113 Sawmills; 321918 Other Millwork), with cross-references. https://www.census.gov/naics/resources/archives/sect31-33.html
7. U.S. Census Bureau — 1997 NAICS Sector 42 definition (wholesalers and services incidental to sales). https://www.census.gov/naics/resources/archives/sect42.html
8. U.S. Small Business Administration — Small business size standards (overview; NAICS assignment per 13 CFR 121.402). https://www.sba.gov/partners/contracting-officials/small-business-procurement/small-business-size-standards
9. U.S. Small Business Administration — Table of Size Standards (current official thresholds by NAICS). https://www.sba.gov/document/support--table-size-standards