Typically, the soil excavated on a site for a residential basement is used as backfill. This soil usually is silty sand, clayey sand, silt, or clay - all soil types that produce lateral pressures greater than 30 psff. What this means is that the concrete contractor and producer often unknowingly build a structure whose design is not based on a rational approach. Unless the residential contractor builds in an area where the excavated soil used as backfill is a clean gravel or sand, the basement wall probably will receive a lateral earth load greater than 30 psff and potentially experience cracking.
The National Ready Mixed Concrete Association has proposed new plain-concrete basement-wall thickness design tables that are based on accepted engineering principles for various recognized soil types. Using the tables, a municipality can adopt one or more equivalent fluid pressures to represent the prevailing soil types in its area. This would allow the same ease of basement-wall thickness selection as with previous tables, but the wall thickness would be based on a rational approach and would be suitable for use with a much wider range of soil types.