The short answer
Electrical, plumbing, gas, HVAC, structural work, and roofing usually need a licensed contractor and often a permit. Day labor is the right answer for the work around those trades, like demo, hauling, digging, and cleanup, and the wrong answer for the licensed work itself.
Where the line usually sits
Most places require a licensed person for anything that can burn a building down, flood it, or make it fall over. Electrical, plumbing, gas, HVAC, structural changes, and roofing are the common ones.
The rules are local. Your city or county building department has the list, and a five minute call answers it for your specific job.
What day labor is genuinely great for
The work around the licensed work, which is most of the hours on a job.
- Demo and tear out before a trade comes in.
- Digging, backfilling, and moving material.
- Hauling, loading, and dump runs.
- Site cleanup at the end of each day.
- Carrying and staging material so the licensed crew is not doing it at their rate.
Permits are yours, not the worker's
If the job needs a permit, the permit is pulled by you or by your licensed contractor. A day laborer cannot pull one for you and should not be asked to.
Work done without a required permit tends to surface at the worst time, when you sell, when you refinance, or when you file an insurance claim on damage it caused.
What unlicensed work costs when it goes wrong
Insurers deny claims that trace back to unpermitted or unlicensed work in the trades that required it. That is the real exposure, and it is much larger than what you saved.
Cities can also order the work torn out and redone properly, which means paying twice plus the fine.
Checking a license takes two minutes
Every state has a license lookup on a .gov site. Search the state name plus contractor license lookup, and put in the name or the number they gave you.
Check that the license is active, that it covers the trade you need, and that the name matches the person actually doing the work. Then ask for their certificate of insurance while you are at it.
A good way to run a mixed job
Hire the licensed trade for the licensed part, and hire day labor for the hours around it. That is cheaper than having a licensed crew carry debris, and it is legal.
Just make sure everybody knows the boundary. Tell the crew plainly what they are not to touch, and tell the contractor which parts are being handled by your own help.
This guide is general information, not legal, tax, or insurance advice. Rules differ by state and by situation, so talk to your own professional before you rely on it.