Do to the slope of our lot and the amount if backfill, the (future) garage floor slab had to be an engineered slab. Unfortunately this is a costly job but there was no way around it as the back fill would settle potentially allowing the garage floor to crack and or collapse. The engineered floor slab has 4 support columns under it going down to solid ground and is reinforced with rebar. The reason this is our “future” garage is because we decided not to build the garage at this time do to finances. We did decide it was worth it to spend the money to put in the foundation for the garage now so that when we get to the garage project later, we don’t have to do any excavation or concrete work. The other advantage to doing the foundation now is that it matches the foundation to the house and it is tied in to the house foundation for greater strength.