How do I know if my particular project requires a Building Permit?

The easiest and surest way to know is to call the office and ask. But pretty much anything short of a swingset or a doghouse requires a permit. The need for permitting is not always based on the structural nature of the project; it can also be to double check that the location of the project meets all Town of Plaistow Zoning Ordinance Setback (Article V, 220-32I) requirements.