Foundation Systems

Introduction u All structures require a foundation u Foundations provide a base to distribute the weight of the building to the soil u Must resist loads from gravity, floods, winds, and earthquakes.

Soil Considerations u Nature of soil –Types/Textures –Bearing capacity/Compaction u Classification/Names of conditions u Climate

Soil Types Bearing Cap u Rock5000 or 20% crushing value u Sand –Course1500 –Fine1000 u Clay –Hard3000 –Sandy2000 –Soft1000 u Adobe1000 u Silt 500

Soil Classifications and Names of Conditions 1--Natural grade 2--Existing grade 3--Finished grade 4--Backfill 5--Compacted Fill 6--Uncompacted Fill 7--Cut

Climate Conditions Frost Depth Chart, see text

Climate Considerations u Freezing –Know local conditions –Depth requirement »12” below average frost depth –Follow design rule for sizing footing »width = 2 x foundation thickness »depth = foundation thickness u Water Content –permeability of soil--water absorbed into soil causes expansion

Type of Foundations u “Tee” or “T” foundation (Continuous or Spread foundation) u Slab (On-grade) foundation –sometimes called monolithic concrete slab foundation u Pier foundation

What the Foundation Looks Like u Spread and Slab Foundations –Sectional view –Plan view Like Class Projec t

Tee Foundation W/ Interior Footings

What the Pier Foundation Looks Like u Pier Foundation –Plan view, Exterior or side view, Perspective

Special Foundation Conditions u Fireplace Footings, extends 6” beyond u Foundation height out of ground (set by code): 6”-8” above grade, usually 8” u Stepped foundation: –32” horizontal minimum –24” vertical maximum u Anchor bolts: 5/8”  x 12” 32” OC u Reinforcing requirements –Rebar sizes given in # of 1/8” diameters. Example #4 = 1/2” Dia. –Range from #2 to #18 diameter

Stepped Foundation

Reinforcing Bars (Rebar) Identification Marks: 1--Steel Manuf (Mill) 2--Bar Size(no. of 1/8 dia) 3--Type of steel(grades) N = new billet steel I = rail steel A = axle steel 4--Minimum yield (psi) 40K, 50K, 60K, 75K

Foundation Dimensioning u Foundation walls –outside surface/jogs/etc. u Piers/beams –always to center of piers or beams u Vents –dimension to actual opening u Access doors –location and size dimensions req’d

Foundation Dimensioning Example

Foundation Vents u Sizing –1 sq ft ventilation for each 150 sq ft of crawl space area –First, determine crawl space area –Second, Area (x) 1/150 = total net vent sized(TNVS) –TNVS (  ) net area of one vent = # vents required (round up) »(Use product supply literature)

Foundation Ventilation 1/150 1/1500

Product Supply Literature

Crawl Space Access u All crawl spaces must have access provided u Type/Location of access –floor to crawl space (possibly in closet or under stairs) –outside access through foundation u Codes vary for size –UBC--18”x30” min –CABO--18” x 24” min –SBC--18” x 24” min –IRC—18” x 24” min

Fireplace Construction and Drafting

Introduction u How many of you have a fireplace in your home? u Is it your major source of heating? u Fireplaces today are more of a luxury item –major element of interior design in living area »provide atmosphere –minor concern for heat

Fireplace Design and Construction u Type and style u Structural framing around fireplace u Size & type of opening u Chimney design/height above roof u Fireplace terminology/function u Flue sizing u Fireplace drawings

Common Fireplace Types 1--Single faced flush hearth raised hearth 2--Double faced corner designs 3--Double faced opposite sides design 4--Three faced 5--Free standing

Double Faced Fireplace

Double Faced Opposite Sides FP

Three Faced Fireplace

Structural Framing Requirements u No wood or combustible material is allowed to touch any part of the fireplace, its foundation, or chimney –2” clearance usually required by code u No structural piece should rest on the fireplace and use it as support

Structural Framing u Note –double headers & trimmers –opening < 10’ –ledger strip or Joist hangers u fireplace & chimney free- standing & self- supporting (from FP below) (or Joist hangers)

Flashing Around Chimney u Note –flashing »callout –saddle or “cricket”-- diverts water away from behind the chimney Drawing callout: 26 GA GI FLASHING

Chimney Heights u Building Code: (2 foot 10 foot rule) –Chimney 2’ minimum above any construction within 10’ of the chimney

Chimney Flues u Area through which the combustion gases and smoke travel u Flue liners –used to prevent deterioration to mortar joints –produces a better downdraft & requires smaller flue (smoother surface) u Unlined Flue –Chimney must be thicker walls than with chimney with flues liners

Chimney Flues u Each fireplace requires a separate flue –may be contained within same chimney –minimum of 4” distance apart –must be different heights, min of 4” from top 4” Min

Chimney u Cap –keeps water away from lining –stops downdrafts u Spark Arrester –screen device that prevents sparks from leaving the chimney & passing onto the roof

Fireplace Terms 1. Firebox--opening8. Damper-- 2. Hearth--min 16” sizes vary prefered 20”9. Throat 3. Ash dump10. Smoke 4. Ash pit chamber 5. Clean out11. Smoke 6. Steel angle or lintel shelf 7. Mantel12. Flue 13. Chimney

Fireplace Terms/Drafting Layout

Fireplace Function Smoke Chamber 1. Transition from the firebox to the flue 2. Responsible for controlling & regulating burning and eliminating smoke & combustion gases Smoke Shelf 1. Prevent downdraft 2. Help divert cold air into smoke chamber Throat 1. Channels smoke into chamber Damper 1. Controls air flow/shut off when not in use

Flue Sizing u Crucial that fireplace opening be in proper proportion to flue for proper operation u Inside free space of flue called effective flue area, expressed as fraction u Effective flue area (EFA) –1/10 minimum allowed (10%) –1/8 preferred (12%)

Flue Sizing u Find affected firebox area –based on type of fireplace –Single faced »Area = h (x) w u Multiply by Ratio –if 30” wide x 26” high –Area = 30 (x) 26 =780 sq in –Effective Flue Area (EFA) –(Considering Min EFA 10%) – Therefore 780/10 = 78 sq in –See tables to select proper flue Dbl-faced Area = 2(h x w) Area = 2(w x h) + d x h Area = h x w

Flue Shapes, Sizes, and Areas u See Text for a similar table to the table below showing flue lining sizes, etc. Table relates only designs for 10% EFA, flue areas are okay

Flue Sizing u find width at bottom u find height at left u find intersection u find nearest curve above intersection

Fireplace Drawings u Required Drawings (see by code or city) –Enlarged Plan view »like the floor plan but to include dimensions to build –Vertical Section »shows all vertical relationships including dimensions –Elevation of Fireplace front view »shows what the fireplaces looks like when finished –Common scales: 3/8” = 1’-0” and 1/2” = 1’-0” –Views are arranges by orthographic projection »height and/or width must align from view to view

Fireplace Assignment (w)

Fireplace Drafting Layout