Foundation contractors can be as obdurate as their medium when it comes to house concrete projects, including reinforcement rebar design.
If they’re engineers, too, this litany won’t surprise ‘em much at all. But most aren’t engineers, too.
There’s good reason for every rebar design standards entry to follow and almost all all self-explanatory; each entry is worth review with your contractor. You’ll get better house concrete foundation reinforcement. The contractor may learn a thing or two.
If the contractor demurs or denigrates, then get another contractor and so will you, with the right contractor.
Now, none of this is – ahem – cast in concrete. House project concrete, that is.
There are conditional and situational latitudes and limits on any job anywhere.
As an owner, go through the salient points and judge for yourself whether you’re going to work with the right contractor or not.
As a designer, adapt this to the overall design and specify, recognizing apparent conditions and situation.
REBAR DESIGN STANDARDS
Rebar (a/k/a of one or another of two types of foundation reinforcements: deformed bar, for its uneven surfaces of several distinctively different configurations that keep it from easily moving in placements; smooth bar, for its absence of deformations on its exterior surfaces, allowing its application latitude in foundation element movements at right angles to its axis)
Shall be fresh and clean
Shall be detailed and accessorized in conformance with not less than Concrete Reinforcing Steel Institute (CRSI) “Manual of Standard Practice," latest edition
Shall always be set on chairs – like wire spiders or napkin caddies that keep rebar from touching the grade at a slab-on-grade bottom of face – (not dobies – little pads – or bricks, jobsite scraps, and the like) for applications on the horizontal
Which chairs shall not be less than Concrete Reinforcing Steel Institute (CRSI), Class 2
Which chairs shall be preferably CRSI Class 1
Which chairs shall not be CRSI Class 3
Shall conform to not less than most recent ASTM A-615 M-04a (a/k/a American Society for Testing and Materials, “Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement") Grade 40-#5 overall, unless otherwise noted
Shall not be in permanent contact with
Earth (same for welded wire mesh)
Water (same for welded wire mesh) or
Ambient air (same for welded wire mesh)
Shall be covered by not less than ¾ linear inch plus aggregate size
Shall not be welded or otherwise heated without express permission from a structural engineer
Rebar Laps, Section in Plan View
Key: CNR = corner; HOR = horizontal; ISC = intersection; NTS = not to scale; RR = rebar; VERT = vertical
Shall be lapped
Not less than the greater of 25 linear inches or 40 bar diameters and
Only to the outside, or exterior, runs, i.e., never lapped to interior runs, at the following sites - see the illustration herein under Rebar Laps, Section in Plan View
Corners and intersections
Along wall lengths (i.e., at other than corners and intersections) and
Shall also be staggered at not less than 4 linear feet
To counteract shear (not tension) in concrete foundation segment replacement
As dowels
Shall be applied by a 3/4 linear inch bore not less than the greater of 9 linear inches or 80% of intersected wall width into existing foundation and
Shall protrude not less than the greater of 9 linear inches or 80% into new foundation
Shall be sealed to existing with appropriate Strong-Tie Adhesive or equivalent
Shall be set on the horizontal
Along the new foundation centerline at not greater than the lesser of
6 linear inches on center on the vertical overall or
8x rebar diameter or
In 2 columns if wall width of either foundation element is not less than 12 linear inches
Shall be set at 3 linear inches from wall top of face and footing bottom of face
As transverse rebar reinforcement
Shall be applied at contractor discretion
May be applied at point, or concentrated, loads
Shall be applied when footing depth is less than wall width, with engineering specification
Shall be applied when footing width less than twice wall width, with engineering specification
Shall be applied when footing is not on-center to wall or other load, with engineering specification
As epoxy-coated rebar
May be applied at contractor’s discretion in which
Bars and application shall conform with not less than
ASTM A-775 M-00b (a/k/a American Society for Testing and Materials, “Standard Specification for Epoxy-Coated Reinforcing Steel Bars")
ASTM A-934 M-00b (a/k/a American Society for Testing and Materials, “Standard Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars")
ASTM A-884 M-01 (a/k/a American Society for Testing and Materials, “Standard Specification for Epoxy-coated Steel Wire and Welded Wire Fabric for Reinforcement")
ASTM D-3963 M-01, (a/k/a American Society for Testing and Materials, “Standard Specification for Fabrication and Job-Site Handling of Epoxy-Coated Reinforcing Bars")
AASHTO M284-97 (a/k/a American Association of State Highway and Transportation Officials, “Standard Specification for Epoxy-Coated Reinforcing Bars" and
AASHTO M254-96 (a/k/a American Association of State Highway and Transportation Officials, “Standard Specification for Corrosion Resistant Coated Dowel Bars")
Shall be applied additionally at not less than 2-#5 rebar on the horizontal centerline of a masonry ledge, at cover of ¾ linear inch plus aggregate size
Shall be applied
In pairs
Not less than 6 linear feet in length each, assuming fit of length with cover of ¾ linear inch plus aggregate size
At either termini
Deformed #5
Set at mid-depth
Set equally into exterior corners at the perimeter, as an arrow’s shaft
Set equally across interior corners at the perimeter, as a see-saw
Set similarly at inside and outside corners interior to the perimeter where abutting slabs-on-grade vary significantly in elevation, as between habitable and garage
Not to traverse a contraction joint at other than right angle
Shall be set in pairs
At entry edge of vehicle garage door
At each concrete stair tread
Before The Architect designs and drafts custom home plans nationwide. Its principals Ralph and Jean Pressel have worked hands-on together since the ‘60s in custom home design, drafting, consulting, plus building and repair in every major trade.Their plan sets are extraordinarily detailed; their clients' active involvement throughout is essential.
Home Design Standards - Home Building Standards 4Q08 Edition e-book at 823 pages and the website www.beforethearchitect.com at nearly 1000 pages of text and illustrations are enterprises of Before The Architect’s principals.
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