I was going to build a free standing deck at the back of my house. The first set of footings would be 1'9" from the concrete basement/foundation for the house. The house is a new construction built one year ago.
reading this site: http://www.finehomebuilding.com/how-to/articles/top-10-deck-building-mistakes.aspx it says
To install deck piers properly, the piers must bear on undisturbed soil and, depending on the region, be set below the frost line. This could mean the need for 3-ft.-deep footings in some areas. However, if the piers are in a backfill region, as is the case with piers nearest the house on a freestanding deck, the footing depth may have to be as deep as 10 ft. to reach undisturbed soil and to comply with code.
I am now worried that these footings may be less stable. Our area requires 18in diameter footings, 30 inches deep.
Some people on this site suggested against using a ledger if possible. The deck is only 3'6" feet above the ground.
Best Answer
Contact the building inspector for your area. They will know whether the whole area around your house was dug and backfilled, or whether the ground is undisturbed. They will also know what is under the dirt and how far down you need to go. I live in a very rural area and my building inspector remembers a TON of details about my house to the extent of not needing to come out for a site inspection pre-build because he remembers from a previous visit. But even in the city there is documentation that the inspector can look up. They want you to be safe so they will help you do what you need to do.