Is 5645 always cheaper than 5403?

No. The illustrative ranges overlap, and in some states 5645 rates higher than 5403 for the same payroll. Don't assume moving to 5403 is a saving without checking your state's published rates.

What if a job is on a triplex or fourplex?

Three or more units generally pushes the job out of 5645's one- or two-family definition and into 5403, even though the work looks like standard residential framing.

Can we split one crew's payroll between the two codes?

Only with verifiable records allocating hours to each job's structure type. Without them, the whole crew's payroll typically goes to the highest-rated code that applies to any of the work.

Does interior trim work on a commercial job still count as 5403?

Not usually — interior trim and cabinet installation generally falls under 5437 regardless of whether the building is residential or commercial. Structure type decides between 5645 and 5403; the type of work decides whether 5437 applies instead.

Code comparisons

Class code 5645 vs 5403: residential or commercial carpentry?

The short answer

The structure the crew is actually working on, job by job, decides it: detached one- or two-family homes are 5645, everything else — commercial, multi-family over two units — is 5403.

Carpentry businesses that started out framing houses and grew into commercial and multi-family work often keep the class code they had on day one. These two codes sit close enough together that switching one for the other isn't a reliable saving — but staying on the wrong one is still a real audit risk.

5403 is the carpentry catch-all: everything that isn't detached residential, interior trim (5437) or one of the other specific carpentry codes falls into it. Getting the split right, job by job, matters more for defensibility here than for a guaranteed premium cut.

The codes side by side

Code	What it covers	Illustrative rate
5645	Carpentry — Detached One- or Two-Family Dwellings	$8.00 – $25.00
5403	Carpentry NOC	$6.00 – $18.00

Per $100 of payroll. National illustrative ranges — your state and carrier set the actual rates.

What kind of structure is this crew framing, on this job?

A standalone single-family home or duplex → 5645 (Carpentry — Detached One- or Two-Family Dwellings)
Even a large custom home stays 5645 as long as it's a detached one- or two-family dwelling.
An apartment building, condo complex or commercial structure → 5403 (Carpentry NOC)
Multi-family over two units moves out of 5645 regardless of how residential the work looks.
Both, across different jobs in the same policy year → 5645 (Carpentry — Detached One- or Two-Family Dwellings)
Without job-level payroll records tying hours to each job's structure type, the whole crew's payroll can default to the higher-rated of the two codes.

When each code applies

5645 — Carpentry — detached 1–2 family dwellings

Structural carpentry on detached one- or two-family homes
Framing, sheathing, roof structure and decks on single-family or duplex jobs
The job site is a standalone residential property, not part of a larger building

5403 — Carpentry NOC

Carpentry on commercial buildings or multi-family properties with more than two units
General structural carpentry that doesn't fit a more specific code
The catch-all when the job type doesn't fit 5645 or the interior-trim code 5437

What audits get wrong here

You overpay

A carpentry company that now does mostly commercial and multi-family framing is still coded 5645 from its early years building single-family homes.

The class code follows the business's original setup, not its current job mix, until someone actually revisits it.

You overpay

A residential-only crew is coded 5403 because that's the company's governing classification for its larger commercial division.

Detached 1-2 family work is a distinct code even inside a company that mostly does commercial work — it doesn't automatically follow the governing class.

You underpay — back-bill risk

A crew working a 6-unit apartment building is left on 5645 because 'it's still houses to us'.

Structure type, not similarity of the work, decides the code. An auditor who finds multi-family jobs on 5645 will move them to 5403 and can back-bill for the period.

You underpay — back-bill risk

Payroll is split between 5645 and 5403 by estimate rather than by job records.

A split without verifiable per-job records doesn't hold up. The entire payroll can be reassigned to the highest-rated applicable code on audit.

Worked example

A carpentry crew that splits its year between single-family framing and 4-unit apartment buildings, currently coded entirely under 5645, on $120,000 of annual payroll.

Charged at 5645 (Carpentry — Detached One- or Two-Family Dwellings): $9,600 – $30,000 / yr
Charged at 5403 (Carpentry NOC): $7,200 – $21,600 / yr

On these illustrative ranges the outcome spans from about $12,000 a year worse to about $22,800 a year better. This is genuinely state-dependent — look up your own rates before arguing it.

Illustrative only. Not a quote, and not a prediction of what your carrier will do.

How much is actually at stake

5645 and 5403 overlap through most of their illustrative range, so there's no guaranteed direction here — reclassifying multi-family work to 5403 can save money or cost more depending on your state's published rates. The real value in sorting this out isn't a fixed saving, it's job-level records that make the split defensible instead of a guess.

What settles the argument

Classification disputes are won with records, not opinions. For this one, gather:

Job-by-job records identifying the structure type — detached 1-2 family, multi-family, or commercial
Contracts or permits showing the property type and unit count for each job
Job-costing reports allocating payroll to each job, not just to the company as a whole
Photographs or site addresses tying specific crews to specific jobs
A written policy for how the office assigns a code to new jobs when they're scheduled

Not sure which one your audit used? Check every employee against their assigned code in a couple of minutes.

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Frequently asked questions

Is 5645 always cheaper than 5403?: No. The illustrative ranges overlap, and in some states 5645 rates higher than 5403 for the same payroll. Don't assume moving to 5403 is a saving without checking your state's published rates.
What if a job is on a triplex or fourplex?: Three or more units generally pushes the job out of 5645's one- or two-family definition and into 5403, even though the work looks like standard residential framing.
Can we split one crew's payroll between the two codes?: Only with verifiable records allocating hours to each job's structure type. Without them, the whole crew's payroll typically goes to the highest-rated code that applies to any of the work.
Does interior trim work on a commercial job still count as 5403?: Not usually — interior trim and cabinet installation generally falls under 5437 regardless of whether the building is residential or commercial. Structure type decides between 5645 and 5403; the type of work decides whether 5437 applies instead.

Other code comparisons

ClassCheck provides self-advocacy information only. This is not legal, insurance or accounting advice, and classification rules vary by state and carrier. Terms.