Working with an engineer, I decided to pour a concrete slab on top of metal deck pans supported from below by steel I-beams. The design called for 10-inch-thick reinforced foundation walls formed with beam pockets and a perimeter shelf to support the steel pans. Two W12x40 I-beams would span front-to-back below the deck pans to support the reinforced slab.
This garage--added on to a log home on a steeply sloping site--has living space above and storage space below. The builder considered several approaches for the foundation and garage floor strong enough to support two vehicles 12 feet above grade.
The steep slope presented a challenge at every stage of construction, starting with the excavation and the removal of several large boulders
The foundation forms tower 12 feet above grade at the back of the garage.
Restricted access made this an ideal job for a pump truck.
Polystyrene insulation panels were used to form the shelf to support the deck pans and I-beams.
Here's another view of the formwork and insulation panels.