Attic is significantly larger on the inside than the outside of the house
We're converting our attic into usable space. Measured the exterior of the house: 32 feet by 24 feet, standard ranch footprint. Went up to the attic to plan the layout and measured 32 by 24... and then 32 by 24 again. There's more attic behind the attic. The roofline from outside does not account for this. I walked the full space. It's roughly twice the square footage it should be based on the exterior dimensions. The extra section is finished (older flooring, plaster walls) and has a window that does not appear on the outside of the house. Through the window I can see my backyard, so it's not looking somewhere else. It's just looking at my backyard from a window that isn't visible from my backyard. Before I start putting drywall up: is this a code issue?
It's a code issue in the sense that the square footage on your property record is wrong and your taxes are probably too low. Whether that's a problem depends on whether you want to draw attention to it. Some people live with spatial non-conformance for decades and never file. The risk is that a future resale inspection catches it and you have to retroactively permit the space, which involves an assessor, a spatial survey, and a conversation with the county about why you've been paying taxes on 768 square feet of attic when you have 1,536. The window that isn't visible from outside is called a "shy window." They're common in houses with spatial non-conformance. The window exists but it's not participating in the exterior facade. It's technically there, it's just not rendering. You can see out but nobody can see in. Some people consider this a feature.
"Not rendering." My house has a window that isn't rendering. Like it's a video game.
Welcome to older Crambleside homes. My neighbor's place has a hallway that's six feet longer on the inside than the outside. He found out when he tried to run ethernet cable from one end to the other and kept running out of cable. The extra six feet aren't on any floor plan. His electrician charges him for the actual distance, not the legal distance, which he feels is unfair. My honest advice: use the space, don't file, and don't measure anything else in the house unless you're emotionally prepared for what you find.
One practical note: if you're doing drywall in the non-conformant section, use standard materials. Do NOT use spatial-grade anything. The space is already extended; spatial-grade products in an already-extended space can cause compounding, which is when the extension extends itself. I've seen a closet do this. It became a room. The homeowner was initially pleased and then very much not pleased when the room became a hallway and the hallway kept going.