Single Carport to Double Garage
I have a single carport, with a 12'x 20' concrete slab (built in 1972). The slab is in great shape. We are looking to expand that to a 20' x 20' closed in garage. Majority of the contractors we have spoken with say they plan to keep the original slab in place and add an additional slab next to it and then build the garage on the new and old slabs. Are there specific design or building considerations the contractors should do to minimize the risk of uneven settling or other "non-uniform" risks associated with two different foundations?