His office was a small building, inside a bigger building? That throws me off.

That's what Demont asked for ... but I knew exactly what he was talking about. Often large industrial shop or warehouse buildings will build a smaller office inside to organize space and protect equipment or paperwork.

In fact my housemates just rented a new shop exactly like that ... a small office will hold the large-format printer and computer in order to protect it while there's all sorts of debris-causing woodworking and metal shop going on in the rest of the place.

Ah, now I get it. To be honest I've never seen such thing/idea before, but it sounds reasonable now thanks to you.

It also fits very well with the characters situation.