Hi there! Been in that exact situation multiple times. Your best bet is looking into compact pile driving tools - they're game changers for tight access sites. These portable units can be carried by two people, fit through standard doorways, and work in spaces where full-size rigs can't go. We used one on a deck project last summer with similar constraints. The handheld helical pile driver got through a 6-foot pathway between a garage and fence line no problem. Installation was quick, minimal soil disturbance, and the crew could stage everything in a small laydown area. Torque readings were consistent, and we hit bearing capacity at depth without any issues. Check out this article for more details:
https://illustrarch.com/articles/64928- ... tools.html - covers torque ranges from 5,600 to 11,000 Nm depending on your soil conditions.