Proper Backfilling Keys

Recommendations and code requirements regarding backfill of newly poured basements are one of the most ignored aspects of foundation construction.

The International Residential Code, American Concrete Institute (ACI) 332 Standard and the CFA Standard all state that foundation walls must be supported at the top and bottom before backfill is placed. Empirical tables presented in each are based on that premise.

The 2006 IRC States:

R404.1.7 Backfill placement. Backfill shall not be placed against the wall until the wall has sufficient strength and has been anchored to the floor above, or has been sufficiently braced to prevent damage by the backfill.

Exception: Bracing is not required for walls supporting less than 4 feet of unbalanced backfill.

A foundation wall is designed as a simply supported beam with restraint at the top and bottom. If there is no support at the top, the wall becomes a cantilevered element requiring a significantly different design, as well as reinforcement requirements for both the wall and footing.

The reality, however, is that most walls are backfilled without the stipulated support. The fact that the walls are much stronger than they need to be to resist designed lateral loads helps keep problems to a minimum but in many cases, backfilling without sufficient support is a problem waiting to happen.

For more information about the requirements and conditions involved in proper foundation design and construction, download the CFA Tech Note: Backfilling Foundation Walls.

Related Content
For more information about the requirements and conditions involved in proper foundation design and construction, download the CFA Tech Note: Backfilling Foundation Walls.
 


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