The International Residential Code is widely adopted in the United States, across all but one of the 50 states (what’s up Wisconsin?), and though it is amended in an unlimited variety across the country, there are some commonalities that can still be found. Along with these common provisions, there are also common mistakes that can lead to a failed inspection.

These mistakes, however common, are not necessarily obvious. Often mistakes come from impatience and innocent ignorance of the code—and from forgetting that the way we once did things is not always the way we should do things. Based on my experience as a longtime (and former) building inspector, here are some of the mistakes that often get flagged on residential building sites.

Failure to Follow Directions

The best way to avoid inspection problems is to both read the manufacturer’s installation instructions and keep copies on file. Many failed inspections result from simply not having instructions on site for the inspector to review. Many re-inspections fail as a result of not following the instructions. As smart as many of us think we are, we can all stand to learn something from the product manufacturer.

Consider pipe threads, for example (see the photo above). Of course, the code requires that they be sealed … or does it? For air-admittance valves, it’s the manufacturer that calls out the thread sealant between the valve and valve fitting. On the other hand, any joint compound, tape, or sealant on the threads of the flare joint on a fuel-gas appliance connector is specifically prohibited in the installation instructions and listing of the product. That’s just one example of why it’s important to read the instructions and have them available for review by your inspector, in case there is any question. (See “Paper Tools,” Tools of the Trade.)