Building Foundations Foundation Walls Footings n A base

Building Foundations Foundation Walls

Footings n A base n Monolithic construction n Independent construction

Foundation-Wall Footings n Spread footings n Undisturbed soil

Footing Design n Prevent settling or cracks n Minimum of 12” below grade. Below frost line n Thickness = thickness of foundation wall n Width = 2 x thickness of foundation wall

Footing Reinforcement n Rebar embedded n 2 lengths of ½” diameter (#4) rebar n Positioned minimum of 3” above bottom

Footing Forms n Form n steel, lumber, or combination of lumber & plywood. n Keyway

Other Types of Footings n Pier and post n Stepped Footings

Footing Drains n 4” diameter pipes at base of footing n Carries water away from house. n Sloped at least 1/8” per foot n Landscaping Fabric

Poured-Concrete Foundation Walls n Durable & water n n n resistant Most building sites Support any type of house 8 – 10” thick Min. compressive strength 2500 psi Most 8’ high

Full Height Walls n Formwork n Reusable forms n Wales

Standard Wall Forms n Wood or metal n Built on site n Prefabricated forms n Snap-ties n 3 – 7 days

Insulating Wall Forms n ICFs (Insulating Concrete Forms) n Permanent n Basic components n planks, sheets, or hollow blocks n Standard wall n Grid wall

Placement n Poured continuously n n without interruption Cold joint Water content Remove Air pockets Concrete vibrator (stinger)

Crawl-space Walls n Advantage – reduced cost n Soil cover n Ventilated n Insulated n Piers support

Reinforcing Concrete Walls n Rebar centered in wall n Lintel

Sill Plate Anchors n Anchor bolts n Metal strap anchors n Sill sealer

Foundation Wall Details n Special features: n Brick-veneer siding n Utility Sleeves

Foundation Vents And Windows n Metal vents n Rust-resistant steel frame windows n Wood framing (pressure treated)

Beam Pockets n Girder flush with top of sill plate

Stripping and Maintaining Forms n Wood wedges (no metal pry bars) n Stiff bristle (not wire) brush n Form-release agent – Bio-slick

Moisture Protection n Bituminous (tar) coating n Top of footings to finished grade level

Backfilling n Filling in excavation area n Too soon, push in foundation walls n First floor framing n Temporary bracing

Concrete Block Walls n Popular foundation walls n No formwork n Blocks inexpensive n Work stopped and started

Concrete Block Basics n Concrete Masonry n n n Unit (CMU) Head Joint Bed Joint Common bond Pilasters Protect from freezing & moisture

Cutting Block n Brick hammer and chisel n Portable masonry saw

Mortar n Mortar bond strength depends on: n n n Type & quantity Workability, or plasticity Surface texture bedding areas Rate at which masonry units absorb moisture from mortar Water retention Skill of person laying block

Mortar Mixtures n Portland cement, hydrated lime, sand, & water. n Prepackaged mortar mix Type N n Type M n Type S n Type O n

Mixing and Placing Mortar n Evaporation n Hydration n 2 ½ hour when air temp is 80ºF or higher n 3 ½ hours when air temp is below 80ºF.

Laying Block Foundation Walls n Skilled masons n Corners built first n Story pole (course pole)

Intersections n Control joint

Tooling the Joints n Weather tight joints & neat block walls n “Thumbprint hard” n Tooling compacts n Head joints, then bed joints

Completing the Walls n Hollow block walls capped n Strengthened with rebar

Moisture Protection n Damp proofed or waterproofed n Parging

Radon n Colorless & odorless radioactive gas n Extremely toxic n Lung cancer n Soluble in water n 9 X heavier than air

Radon-Resistant Construction n Gas-permeable layer n Soil-gas retarder n Sealants n Vent pipe n Cap course

Review 1. 2. 3. 4. 5. 6. 7. What is the minimum depth required for an exterior-wall footing? Describe the type and position of reinforcement that is commonly added to strengthen a footing. What is a keyway and how is it formed? For nearly all poured-concrete foundation walls, formwork must be constructed for each wall face. What holds the formwork together? What creates a cold joint? Why are the joints in a concrete block wall tooled? When using mortar, why is it helpful to know the differences between hydration and evaporation?