NH Building Codes
These can be more complex than simple project like a deck.
https://www.nh.gov/safety/boardsandc...ebldgcode.html ( I Googled NH Building codes) (I take that back. I Googled building codes" and got nothing, but Chrome/Google suggested "Building Codes NH", "Building codes MA", etc.)
Most lumber yards have plans for a variety of projects, and the good deal is, not only does it meet code, you get a materials list. I bought a set of plans many years ago (pre-internet) and modified to fit my space. Way overbuilt, I'm sure, but the vendor probably wanted to be sure that if an amateur messed up, it would still be sturdy and defensible.
I Googled "deck construction plans" and got several sites with design tools, instructions, materials lists, etc.