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Chapter 33. Foundation Systems. Introduction. All structures are required to have a foundation Provides a base to distribute weight onto soil Must be evenly distributed to prevent it from compressing the soil Must resist floods, winds, earthquakes, and floodwater debris. Soil Considerations.
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Chapter 33 Foundation Systems
Introduction • All structures are required to have a foundation • Provides a base to distribute weight onto soil • Must be evenly distributed to prevent it from compressing the soil • Must resist floods, winds, earthquakes, and floodwater debris
Soil Considerations • Soil texture • Affects ability to resist load of foundation • Bearing capacity must be known • Structures built low bearing capacity soil require footings
Soil Considerations (cont’d.) • Compaction methods • Static force • Impact forces • Vibration • Freezing • Foundation should be built to a depth where ground is not subject to freezing • Expansion and shrinking can cause cracking
Soil Considerations (cont’d.) • Water content • As soil absorbs water, it expands • Causes foundation to heave • Resisted through proper drainage and reinforcing foundation and floor slab • Radon • Cancer-causing gas • Structures built in areas with high levels must provide protection
Types of Foundations • Piling foundation system • Beams are placed between vertical supports (i.e., piling) to support structural loads • Steep hillsides • Where structure load exceeds soil bearing capacity • Sites subject to flooding or natural forces that cause large amounts of soil to be removed
Types of Foundations (cont’d.) • Continuous or spread foundation • Most common for residential construction • Consists of a footing and wall • Concrete strength must be specified • For areas of soft soil or fill material, reinforcement steel (i.e., rebar) is used
Types of Foundations (cont’d.) • Grade beams • Added support for a foundation in unstable soil • Fireplace footings • IRC requires minimum footing 12" deep and extend 6" past fireplace face • Veneer footings • Must be wide enough to provide adequate support
Types of Foundations (cont’d.) • Foundation wall • Vertical wall • Extends from top of footing to first-floor level • Usually centered on footing to spread loads • Follow IRC and municipal requirements
Types of Foundations (cont’d.) • Additional considerations for the foundation wall • Stem wall construction • Anchor bolts • Termite protection • Wood floor support • Wood floor ventilation and access • Foundation wall insulation and reinforcement
Types of Foundations (cont’d.) • Retaining or basement walls • Extends full height between basement floor and main floor level • Primarily made of concrete blocks, poured concrete, or concrete-filled insulated concrete foam blocks • Material used will depend on area trends
Types of Foundations (cont’d.) • Additional considerations for retaining or basement walls • Retaining wall reinforcement and anchorage • Moisture protection • Foundation windows • Treated-wood basement walls • Pressure-treated lumber can be used to frame crawl space and basement walls
Types of Foundations (cont’d.) • Partial-height retaining walls • When a structure is built on a sloping site, retaining wall will not need to be full height • More problems are encountered
Types of Foundations (cont’d.) • Interior load supports • Supported on spot footings or piers • Metal connectors • Used at the foundation level to resist stress from wind and seismic forces