BCAB #1474 - Step Footings, Articles 220.127.116.11, 18.104.22.168, 22.214.171.124 & 126.96.36.199
October 21, 1998
Re: Step Footings, Articles 188.8.131.52, 184.108.40.206, 220.127.116.11 & 18.104.22.168
The project in question is a new single family dwelling on a sloping site.
Reason for Appeal
Footings and foundations are regulated by Subsection 9.4.4. and Section 9.15. Article 22.214.171.124. details design requirements for conditions where allowable bearing pressure decreases within a specified distance below the footing/foundation. Article 126.96.36.199. requires a footing under walls unless the safe loadbearing capacity of the soil is not exceeded. Article 188.8.131.52. requires footings to rest on undisturbed soil or rock or compacted granular fill. Article 184.108.40.206. specifies the maximum rise and minimum run of step footings.
The appellant contends that the step footings do not need to be connected by vertical "risers" as long as the safe loadbearing capacity of the soil or rock and footings is not exceeded. There is no difference in principle between this method and the grade beam/column/pad method.
Building Official's Position
The building official maintains that the excavated and disturbed soil at the ends of the footings (top of the "riser") does not provide adequate support to the extent that the foundation walls would in fact be holding the footings up rather than the footings supporting the walls. Also, when the wall is backfilled the unconnected footings will cause a stress point in the foundation wall at each step. There is a four foot step which exceeds the maximum permitted rise of two feet (600 mm).
Appeal Board Decision #1474
It is the determination of the Board that the unconnected step footings do not comply with the intent of Article 220.127.116.11. The Board considers this Article requires the footing to be continuous under the wall in order that the safe loadbearing pressure will not be exceeded at any point under the foundation. If it is desired to use independent footings connected only by the wall above, in a fashion similar to a grade beam on columns, then the wall must be engineered as a beam using Part 4 of the Code.
George R. Humphrey, Chair