A. General: Concrete shall reach a minimum compressive strength of three thousand (3,000) PSI within twenty eight (28) days.
1. Materials: See section 8-303 of this article.
2. Maximum slump: six inches (6").
3. Calcium chloride may be used as an accelerator and shall be introduced in solution as part of the mixing water. Calcium chloride shall not exceed one percent (1%) mixed at the plant per ASTM D98-87.
4. All concrete shall be air entrained, six percent (6%) plus or minus one percent (1%). Air entraining admixtures shall conform to ASTM C260-86.
B. Quality Of Concrete:
1. Job Mix: minimum cement proportions, by volume. One part Portland cement, two and one-half (2 1/2) parts sand, three (3) parts coarse aggregate (3/4" to 1" maximum size).
2. Commercial Ready Mix:
a. Minimum Portland cement content: Five (5) bags/cubic yard.
b. Mixing period shall not exceed beyond one and one-half (1 1/2) hours per batch.
3. Exposed Concrete (Driveways, Sidewalks, Curbs And Gutters, Patios, Stoops, Etc.):
a. Minimum Portland Cement Content: Six (6) bags/cubic yard for three-quarter inch (3/4") to one inch (1") maximum size aggregate.
b. Maximum Slump: Four inches (4").
c. Maximum Water Content: Including moisture in the aggregate: six (6) gallons per bag of cement.
C. Forms:
1. Double forms required for all basement concrete foundation walls.
2. Side forms required for footings where soil conditions prevent sharp cut trenches.
3. Build tight, straight, plumb, and brace rigidly.
4. Forms to be oiled prior to placement.
5. Stepped foundations - forms shall not cantilever more than six inches (6") beyond the excavation below to allow for proper bearing.
6. Wood footing forms, form ties and braces shall be removed prior to backfill.
D. Placing:
1. Place continuously unless otherwise allowed by the Building Official.
2. When not placed continuously, provide a bulkhead with keyway and dowels.
Clean, score, and wet the top surface of the concrete before continuing.
3. Spade, rod or vibrate thoroughly. Concrete shall not be pulled with a vibrator.
4. Concrete shall not be placed on standing water, frozen ground or snow. Bottom of footing shall be cleaned of all soft soils and organic materials.
5. Where ambient outside air temperature is twenty (20) degrees and rising, placed concrete shall be protected from freezing until cured by methods acceptable to the building official. Where ambient outside air temperature is between zero (0) degrees and twenty (20) degrees placed concrete shall be adequately protected with an external heat source until cured. No concrete shall be placed where the ambient outside air temperature is zero (0) or below.
E. Curing And Protection: Concrete shall be protected from drying or freezing and shall be cured in accordance with ASTM C309-89.
F. Loading: Allow sufficient time for strength of concrete to develop before subjecting to loads or traffic.
G. Reserved:
H. Footings:
1. General:
a. Design for proper distribution of superimposed loads.
b. Material: Cast in place concrete.
c. Bear on solid, unfilled ground.
d. Reinforce with steel bars where footings cross or bear on filled trenches or other unstable soil.
e. Footing dimensions listed below are based upon soils or average bearing
capacity three thousand (3,000) pounds per square foot. For soils of lesser bearing capacity where unusual loading conditions exist, larger footings will be required.
2. Wall Footings: Minimum dimensions for spread footings shall be eight inches (8") deep by sixteen inches (16") wide, except that masonry veneer on frame and solid masonry walls shall be ten inches (10") deep by eighteen inches (18") wide.
a. Omission of footings for one or two story buildings of frame or frame with brick veneer or one story solid masonry containing no basement or crawl space is
permitted where soils permit.
b. Footing must be keyed a minimum of two inches (2") into undisturbed soil, or shall be interlocked to the soil by other approved methods.
c. Provide two inch (2”) by two inch (2") keyway in the top of the footing underneath the centerline of the wall.
3. Pier, Post And Column Footings (Interior):
a. Minimum area: 6.25 square feet (30" x 30"), thickness: twelve inches (12") minimum.
4. Chimney Footings:
a. Dwellings; minimum thickness, twelve inches (12"); minimum projection each side, six inches (6”).
b. Pour integral with wall footing when chimney occurs in outside wall or inside bearing wall.
c. Material: Concrete cast in place.
I. Footing Drain Tile:
1. Required on the outside of all footings, minimum diameter, four inches (4"), where there is a basement or crawl space.
2. Cover tile with twelve inches (12") gravel or crushed stone containing no fine particles.
3. Connect to an approved outlet.
4. Provide drains in all window wells and below grade stair landings. Connect drains to drain tile with T-joints.
J. Concrete Foundation Walls Cast In Place: (For masonry unit foundation walls. See subsection 8-305 B. of this article.)
1. General:
a. Materials: See section 8-303 of this article.
b. Walls Supporting Frame Construction: Extend concrete not less than six inches (6") above adjoining outside finished grade.
c. Walls Supporting Masonry Veneered Wood Frame: Extend foundation of that wood portion of wall is not less than six inches (6") above outside finished grade.
2. Minimum Thickness:
a. Not less than eight inches (8"), or that of wall supported, whichever is greater for wood frame structures without masonry veneer.
b. Supporting porch slabs, steps and one story accessory wood frame structures without basement; minimum eight inches (8").
c. Interior walls not subject to lateral pressure six inches (6") minimum.
d. All other walls, ten inches (10") minimum.
3. Girder Pockets: Provide four inches (4") end bearing on main wall for girder. Form pocket for wood girder one inch (1") wider than girder.
4. Sill anchor bolts to be installed.
a. Diameter, one-half inch (1/2") minimum.
b. Minimum length, ten inches (10") (minimum of 7 inches embedded in concrete).
c. Provide washer under nuts on bolts.
d. Spacing, not more than eight feet (8') on center; minimum two (2) bolts in each piece.
5. Anchorage For Intersecting Walls And Slabs: Provide dowel bar anchorage for porch and terrace slabs, concrete or masonry steps and wing walls, which adjoin foundation walls. For basementless portions and attached garages, embed four (4) 1/2-inch round hooked bars four feet (4') long in main wall, two (2) near top and two (2) near bottom of attached wall. Where new foundation walls adjoin existing
foundation walls, they shall be attached with a minimum of four (4) 1/2-inch round dowel bars at each point of attachment.
6. Chimney Foundations: Start at level of lowest foundation wall footings.
7. If special or unforeseen soil conditions warrant, the Building Official may require either reinforcement of wall or increased thickness.
8. Damp proofing and waterproofing.
K. Concrete Floor Slabs On Ground:
1. Construction:
a. Fill Under Slabs: Gravel, sand, screenings, or crushed rock, minimum thickness four inches (4"). Earth under-fill thoroughly leveled and free from vegetable matter thoroughly tamped. No floor slab to be placed in water or on a soft, wet sub-grade.
Basements must be pumped dry at least twenty four (24) hours before floor is poured.
b. Wire Mesh Reinforcing: Six inch (6”) by six inch (6") #10 required in all slabs used for driveways or garage floors. Overlap joints and tie every four feet (4').
c. Bottom Of Slab: Not lower than top of footing. Provide at least four inch (4") bearing on footing.
2. Cement Floor Finish:
a. Finish basement slab with steel trowel.
b. Integral finish on concrete slab.
3. Slabs on ground used as base for floors or as a finish floor in habitable rooms:
a. Minimum thickness, four inches (4").
b. Provide vapor barrier directly under slab, at least six (6) mil thick polyethylene.
4. Basement Floor Slabs: Minimum thickness, four inches (4"). Provide vapor barrier directly under slab, at least six (6) mil thick polyethylene.
5. Required Garage Floor Slabs: Minimum thickness, four inches (4").
6. Stoops, Terraces And Porch Floor Slabs:
a. Minimum thickness, four inches (4").
b. Install flashing between slabs and all wood construction. (See subsection 8-311 F. of this article.)
c. Wing wall support with #4 rebar required for concrete stoops.
7. Slabs on ground used to support interior bearing walls or partitions: Thicken to at least ten inches (10") for a width of twenty inches (20").
8. Pea gravel shall not be used for fill under unconfined slabs such as sidewalks, stoops, etc.