Building Foundations Foundation Walls
Footings A base Monolithic construction Independent construction
Footings - A base that provides a larger bearing surface against soil for load-bearing parts of structure. Generally made of concrete poured into place In Monolithic construction the footing and
Building Foundations Foundation Walls
Footings A base Monolithic construction Independent construction
Footings - A base that provides a larger bearing surface against soil for load-bearing parts of structure. Generally made of concrete poured into place In Monolithic construction the footing and foundation are poured as a single unit. Independent construction - We will focus on separate installation of footings.
Spread footings Undisturbed soil Foundation-Wall Footings Spread footings – generally size is specified on plan. Depth & width determined by loads it must bear, bearing capacity of soil, & local codes. Must always rest on undisturbed soil. Reduces chance for uneven settling of foundation.
Footing Design Prevent settling or cracks
Minimum of 12” below grade. Below frost line Thickness = thickness of foundation wall Width = 2x thickness of foundation wall Footing Design Proper footings prevent settling or cracks in foundation wall. Should be placed minimum of 12” below grade. In cold climates must be below frost line. Often footings are placed deeper than code to form basements. Width of footing depends on soil bearing capacity and is specified by local codes. General guide line for footings on standard soil: Thickness should be equal to thickness of foundation wall; Width should be twice the thickness of foundation wall.
Rebar embedded 2 lengths of ½” diameter (#4) rebar Positioned minimum of 3” above bottom Footing Reinforcement Strength greatly improved when rebar is embedded in it. Usually 2 lengths of ½” diameter (#4) rebar. Must be positioned minimum of 3” above bottom of footing.
Footing Forms Form Keyway
steel, lumber, or combination of lumber & plywood. Keyway Footing Forms - created by pouring concrete into dirt trenches or into a form. Form is any framework designed to contain wet concrete. Can be made of steel, lumber, or combination of lumber & plywood. Commonly 2X lumber with bracing to prevent spreading when filled with concrete. Often assembled with duplex head nails to make disassembly easy. Keyway should be formed in top of footing. Locks foundation wall to footing. Helps prevent leaks between wall & footing. Created by 2x4 pressed into concrete after pour and removed after curing.
Other Types of Footings
Pier and post Stepped Footings Other Types of Footings Pier and post – Block of concrete usually separate from main foundation. Often used to support decks. Stepped Footings – Often used on a lot that slopes. Instead of being at same height around entire foundation these footings “step” down the sloped site.
Footing Drains 4” diameter pipes at base of footing
Carries water away from house. Sloped at least 1/8” per foot Landscaping Fabric Footing Drains 4” diameter pipes placed alongside base of footing on top of gravel bed. Usually connected to storm sewers. Many small holes along bottom edge of pipe. When water rises into pipes it is carried away from the house. Should be sloped toward drain at least 1/8” per foot. After placed covered with filter fabric (landscaping fabric). Allows water through but prevents soil from getting in and clo