Now, remember, we’ve been over the plans, but we really need to make sure that everything is up to code. The home inspectors here are pretty thorough, so please make sure you follow the plans exactly. And remember the carpenter’s rule of thumb: measure twice and cut once.
What does “up to code”exactly in here construction context mean?
A "code" can mean a set of laws. In the United States, building codes are actually different in every town.
According to the building code in our town, shower faucets need to have an anti-scald valve that prevents the water temperature from exceeding 110°F (about 43°C).
When we replaced our shower, we had to have the building inspector come and check to see it was "up to code"--that it met all the rules.
Among other things, he turned the water on, set it to the hottest temperature, and put a thermometer in it.
In the USA, at least, there are standards for all construction, and these are published as legal statutes or legal code. All construction must be "up to code".
Anyone creating a building or structure not "up to code" and be sued in court of law for damages or violations of written contract.