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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. - PowerPoint PPT Presentation
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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
Dimensioning Foundation Components