UPDATE 3: Footings and Foundation
We’re laying the foundation, and making way for utilities, so we can start to build the new garage and ADU.
The new garage and ADU will be supported by frost footings. The footings guard against settling and slippage that can damage the new structure. They also keep posts and beams from direct contact with the earth. Going below the frost line helps prevent soil movement due to frost called “frost heave”.
Clean fill is brought in for backfill and to prep for the new slab. The sand compresses and compacts easily and tightly to create a good solid surface to build on. We’re replacing the excavated soil because it contains roots and stones that might prevent it from compacting, which could create voids and sinkholes, leading to foundation damage.
Sand helps the new garage concrete slab and driveway in a couple of ways. First, it creates a good drainage plane over our sub-soil/existing soil, and it also aids in working the concrete slab to get a nice level surface. The soil removed at excavation is taken away and repurposed or used in re-grading the yard as needed.