NAICS Codes for Construction: Your Guide to Finding the Right Classification

A NAICS (North American Industry Classification System) code is a six-digit number that identifies your business industry. For construction firms, your NAICS code determines which federal solicitations you can bid on, what size standards apply to your firm, and whether you qualify as a small business under SBA rules. Finding and maintaining the correct NAICS code is the first step to winning federal construction work.

What Is a NAICS Code and Why Does It Matter for Federal Bids?

The NAICS system was developed by the U.S. Census Bureau, Statistics Canada, and Mexico's INEGI to classify all North American businesses into industries. Every federal contractor must register at least one NAICS code in SAM.gov (the System for Award Management). The code acts as the key that unlocks access to bid opportunities in your field.

When you register your firm on SAM.gov, you'll designate your primary NAICS code and may add secondary codes that represent other services you offer. Federal agencies use these codes to define their solicitation eligibility rules. A general contractor with NAICS 236110 (Residential Building Construction) might not qualify for a GSA solicitation targeting NAICS 236210 (Industrial Building Construction), even if the work seems similar. The code matters because:

• Bid Opportunity Access: Agencies filter solicitations by NAICS. Miss the right classification, and you'll never see relevant opportunities.
• Size Standard Eligibility: Each NAICS code has its own small business size threshold. One code might cap small-business revenue at $27.5 million; another at $35.5 million. Misclassification can disqualify you.
• Set-Aside Compliance: SBA set-aside and 8(a) contracts are often restricted to specific NAICS codes. You can't claim a preference you don't qualify for.

Federal contracting data is searchable by NAICS. If an agency posts a 15-day construction solicitation on SAM.gov and filters by NAICS 237310 (Highway, Street, and Bridge Construction), your firm won't appear if you registered under 236110 (General Residential Building Construction), even if your team has highway experience.

Common NAICS Codes for Construction Contractors

Construction is broad, and the NAICS system reflects that. Here are the primary codes most construction firms operate under:

Your firm may qualify for more than one code. A general contractor doing highway work and building construction might register under both 237310 and 236110. The key is accuracy—claim only codes that genuinely describe your work, or SAM.gov compliance reviews can flag inconsistencies.

How to Find Your Construction Firm's NAICS Code

Step 1: Check the Census Bureau's NAICS search tool. Visit www.census.gov/naics and search for construction-related keywords (e.g., "general contractor," "excavation," "painting"). The search results show definitions and cross-references.

Step 2: Compare to your scope of work. Read the NAICS code definition carefully. Does your firm perform the primary activity described? For example, if you're a general residential contractor but also do landscaping as a minor service, landscaping (561730) doesn't become your primary NAICS. Your primary code should match your largest revenue stream and main business focus.

Step 3: Verify size standards. Once you've identified your likely code, check SBA's size standard table (www.sba.gov/size-standards). This table lists every NAICS code with its small-business revenue or employee cap. Your firm must not exceed that threshold to claim small-business status. If you're 15 employees and the construction code you found has a 500-employee threshold, you're clear. If it's 50 employees and you're at 40, document your exact headcount.

Step 4: Confirm with SAM.gov and your auditor. When you initially register or renew your SAM.gov registration, you'll enter NAICS codes. Review your current registration to see what you already claimed. If your firm has received past federal contracts, your original NAICS may still be on file. Confirm it's still accurate. If you've added service lines or shifted focus, you may need to add secondary codes.

Step 5: Document your decision. Keep a brief record (email or memo) of why you chose your NAICS. If an agency later challenges your classification, you'll have evidence that it reflects your genuine business activity, not an attempt to game eligibility.

NAICS Code Misclassification: Risks and How to Avoid Them

Misclassifying your NAICS code can have serious consequences:

• Contract Termination: Federal agencies can terminate a contract for a material misrepresentation of NAICS, size, or ownership status. This can mean returning fees and suffering reputational damage.
• Suspension or Debarment: Repeated or fraudulent misclassifications can trigger suspension from federal contracting or debarment (a permanent or temporary ban).
• Audit and Recovery: If your firm won an 8(a) contract or SBA set-aside and you weren't genuinely small or in the right NAICS, SBA may audit and require contract proceeds to be returned.
• Lost Bid Opportunities: If you're classified as the wrong industry, you simply won't see relevant opportunities.

Common Misclassification Mistakes

Many firms misclassify in order to claim small-business status or to appear in larger bid pools. Others get it wrong unintentionally—they registered 10 years ago and never updated as their business evolved. Here's how to stay compliant:

• Don't claim secondary NAICS codes for work that generates less than 10–15% of revenue. SAM.gov expects your primary code to account for the majority of work.
• If you perform both highway and building construction, register both codes but clearly label which is primary.
• Update your SAM.gov registration within 30 days of any major business change (acquisition of another firm, significant shift in service lines, merger, or if you fall above a size standard threshold).
• If you're unsure, consult your industry association or SBA district office. The SBA's Answer Desk (1-800-827-5722) can help clarify NAICS classifications.

Using Your NAICS Code to Search SAM.gov for Construction Bids

Once you've confirmed your NAICS, you can use it to search SAM.gov and uncover opportunities tailored to your firm. Here's the practical workflow:

1. Log in to SAM.gov and click "Opportunities" (or use the advanced search).
2. Filter by NAICS code: Enter your primary NAICS or a range. For example, if you're a general residential contractor (236110), search that code plus any secondary codes where you're genuinely active.
3. Set classification filters: Choose the solicitation type (competitive set-aside, 8(a), HUBZone, women-owned, etc.) that your firm qualifies for.
4. Sort by response deadline: Federal construction solicitations typically offer 10–21 calendar days from posting to response deadline. Some large or complex projects allow 30+ days. You'll see the deadline clearly in each solicitation. Note that amendments can extend or shorten deadlines.
5. Track amendments: Every time an agency updates a solicitation (adds documents, clarifies requirements, extends the deadline), it posts an amendment on SAM.gov. Missing an amendment can mean missing a critical deadline shift. Tools like BidWatch watch your NAICS codes and send alerts when new opportunities and amendments are posted, so you don't rely on manual SAM.gov checks.

A real example: In early 2024, the Army Corps of Engineers posted a highway repair solicitation (NAICS 237310) with a January 15 deadline. On January 8, they amended it to extend the deadline to January 22 due to incomplete site documents. Contractors who checked SAM.gov once on posting day but didn't monitor amendments missed the extended window and couldn't bid. Contractors using automated bid tracking caught the amendment immediately.

FAQ

What if my construction firm does multiple types of work—do I need multiple NAICS codes?

Yes, you can register multiple NAICS codes in SAM.gov. Your primary code should represent your largest revenue stream. Add secondary codes only if they're material (generally 10%+ of annual revenue). If you do 80% general building construction and 20% electrical subcontracting, register 236110 as primary and 238210 as secondary. Don't register a third code for landscaping if it's a one-off service—it creates confusion and triggers audits.

Can I change my NAICS code after I've won a contract?

You cannot retroactively change the NAICS code you claimed when you bid and won a contract. Changing it mid-contract or after award is considered a material misrepresentation. If you genuinely misclassified at bid time, disclose it to the contracting officer immediately and request a determination. Most agencies will allow a correction if it was made in good faith and doesn't affect your size or ownership status. Never try to hide or silently change it.

How often should I review my NAICS code?

At minimum, review it when you renew your SAM.gov registration (every 12 months). If your business changes significantly—you acquire another firm, add a new service line, or merge with a competitor—review and update within 30 days. Agencies audit this during proposal evaluation and post-award compliance checks, so staying current protects you.

Does my NAICS code determine if I'm a small business for federal purposes?

Your small-business status is determined by your NAICS code and your revenue or employee count. Each NAICS has its own size standard (e.g., $35.5 million in revenue for most construction codes). You must satisfy two criteria: you must be independently owned and operated, and you must not exceed the size standard for your NAICS code. If you're a sole proprietor with $2 million in annual revenue under NAICS 236110, you're small. If you're a corporation with $40 million in revenue under the same code, you're not. The NAICS code is half the equation.