Foundation Systems

Standard ACT-ADDI-6 Students will prepare foundation plans. Explain the purpose of foundation plans. Identify different foundation systems and terminology. Draw and dimension foundation plans.

Purpose To provide a base to distribute the weight of the structure onto the soil It must be evenly distributed over a large enough area to prevent compression of the soil Must resist floods, winds, and earthquakes Floods can wash away supporting soil Wind pushes against houses, pushing them up Must move with the ground in an earthquake

Soil Considerations Bearing capacity of soil must be known before foundation can be designed Bearing capacity: amount of weight a square foot of soil can support Freezing – foundation should be built below freezing level In Georgia – under 10” In Minnesota – up to 100”! Water content – soil will expand and contract with water

Types of Foundations Pilings Continuous (Spread) Foundations Grade Beam

Piling Foundation System Uses beams placed between vertical supports (piling) to support structural loads When structural load exceeds bearing capacity of soil Used on steep hillsides Site subject to flooding Pilings are typically made of concrete with steel reinforcement Where load imposed by the structure exceeds the bearing capacity of the soil On steep hillside sites where it may not be feasible to use traditional excavating equipment On sites subject to flooding or other natural forces that might cause large amounts of soil to be removed (coastal property and sites near inland bodies of water)

Continuous Foundation Most common in residential construction Consists of a footing and wall Footing: base of the foundation system; made of poured concrete Footing can be bonded to the foundation wall with a key or with steel - Footing: placed so it extends below freezing level; size of footing based on soil-bearing value and the load to be supported Keyway: place a 2 x 4 in the top of the concrete footing while the concrete is still wet, once concrete has set 2 x 4 is removed then keyway is left in concrete; when concrete wall is poured it will form a key by filling in the keyway Steel: stronger bond, steel used to tie the footing to the foundation wall

Grade Beam Foundation Provides added support Grade beam is placed under the soil below the stem wall and spans between stable supports - Stable supports may either be a piling or stable soil - Depth and reinforcing required for a grade beam are determined by the load to be supported

Fireplace Footing Masonry fireplace will need to be supported by a footing 12” deep footing that extends 6” past the fireplace on each side

Veneer Footings An extension of the footing and must be wide enough to provide support for the veneer

Foundation Wall Vertical wall that extends from the footing to the first floor Centered on the footing to help evenly spread the load Height of the wall must extend 6” above the ground

Retaining/Basement Wall Walls that extend full height between the basement floor and main floor level Basement walls made of poured concrete or concrete blocks (or wood, depending on the building trends of your area) Used on sloped lots

Interior Supports Spot footings – also known as piers – match the depth of footings

Pedestals A column built on top of a footing Used when upper soils are unstable

Metal Connectors Used to anchor the house to the foundation

On Grade Foundations Slab