Roof Terms
• Span– Distance across the building
Roof Terms
• Run– 1/2 the distance across the building (1/2
span distance)
Roof Terms
• Rise– The distance the roof rises (distance from
the square of house to ridge)
Calculating Roof Surface
• Calculate horizontal area• Determine slope factor (ratio between run and
hypotenuse of the roof pitch
• Multiply slope factor times horizontal area.
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75 feet
35 feet
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FOUNDATIONS
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FoundationsLuke 6: 48-49
48. “He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock.”
49. “But he who heard and did nothing is like a man who built a house on the earth without a foundation, against which the stream beat vehemently; and immediately it fell. And the ruin of that house was great.”
FOUNDATION FAILURES STAND OUT
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3 BASIC REQUIREMENTSA foundation must:
• Not be susceptible to collapse,• Not allow settlement to occur which
results in damage or failure of the superstructure to function as it should, and
• Be feasible and buildable without affecting surroundings.
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Foundation Design Factors
• Loads & Pressures• Soil• Climatological and water control (Frost,
drainage, etc.)
Loads & Pressures
• Foundation walls must be strong enough to resist applied loads
FOUNDATION LOADS
• Dead loads• Live loads• Wind loads• Other horizontal loads (?)• Buoyant loads• Earthquake (seismic) loads
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SOIL TYPESROCK
SOILBOULDERS
COBBLES
GRAVEL
SAND
SILT
CLAY
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Soil Types Bearing Capacity
• Rock 4000 psi or 20% (crushing value)• Gravel 2000• Sand
– Course 1500– Fine 1000
• Clay– Hard 3000– Sandy 2000– Soft 1000
• Adobe 1000• Silt 500
Bearing capacity of the soil depends on soil composition and moisture content
Climate Considerations
• Moisture/Water Content– permeability of soil--water absorbed into soil
causes expansion, thus causing the foundation to heave
• Surface and ground water must have proper drainage– Codes require finish grade to slope away from the
foundation at minimum slopes: • planted--1/2”/12” 6 foot away from building• paved areas--1% slope
Climate Considerations
• Freezing– Water expands as it freezes– Expansion and shrinking of the soil causes
heaving in the foundation– General depth requirement/guideline
• 12” below average frost depth
– Design for sizing footing is determined by the calculations done by the architect or engineer considering loads and soil conditions or using code, depth may follow the rule given above
Climate ConditionsFrost Depth Chart
FOUNDATION SELECTION
PRIMARY• SUBSURFACE AND GROUND WATER• STRUCTURAL REQUIREMENTS
SECONDARY• CONSTRUCTION METHODS• ENVIRONMENT• CODES / REGULATIONS• IMPACTON NEARBY FACILITIES• TIME AVAILABLE FOR CONSTRUCTION• CONSTRUCTION RISKS
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TYPES OF FOUNDATIONSDEEP
• CAISSONS• PILES
SHALLOW• COLUMN FOOTINGS• WALL FOOTINGS• SLAB ON GRADE• MATS• FLOATING
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Pilings• Cast-in-Place
concrete piling shapes
• Steel Piling Detail Drawing
Caisson Rebar Cage
20http://www.azarbuilders.com/gallery/caisson1.jpg
COLUMN / WALL FOOTINGS
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Pier Foundations• Pier foundation resemble pedestal
foundations• Pier Foundation Drawing Representations
Grade Beams• Replaces footings
in unstable soil• Grade beam
becomes an actual beam support by pilings or large pier footings
Mat Foundation
24http://www.irvinegeotech.com/projects.htm
Stepped Foundation
Most Codes give limits:
• Height of step = 24” maximum
• Run of step = 32” minimum
Slab or Monolithic Foundations
• On-Grade Slabs-- called Monolithic if foundation and slab are poured together
• One Placement Two Placements
Foundation Reinforcement
• Concrete & Masonry Resists Compressive Forces
• Concrete & Masonry lousy in resisting Tensile Forces
Foundation Wall Reinforcement
• Reinforcing Bar (Rebar) is placed in the foundation wall to resist possible lateral and bending forces.
Footing Reinforcement
• When the footing is placed near conditions of expansive soil, the bottom of the footing will bend, placing the footing in tension.
• Steel reinforcement is placed in the bottom of the footing to resist the forces of tension in concrete.
• The distance from the bottom of the footing:– Cover varies (1 ½” to 3” coverage) depends on size of
reinforcement and exposure conditions. (formed, not formed, in contact with soil or not, environment, etc.)
Slab Reinforcement
• WWF is used to help the slab resist cracking
• Also placed near the surface in grid patterns to help resist tension in bending
• Steel rebar can also be used to prevent bending of the slab due to beam action in the slab
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SETTLEMENT
• UNIFORM SETTLEMENT• DIFFERENTIAL SETTLEMENT
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