What Size is #4 Rebar? A Technical Guide for Construction Professionals
#4 rebar is a foundational element in reinforced concrete structures, offering a balance of strength and versatility. This guide details its dimensions, compliance with industry standards, and best practices for optimizing performance in construction projects.
Technical Specifications of #4 Rebar
Diameter and Weight
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Nominal Diameter: 1/2 inch (12.7 mm), as defined by ASTM A615 standards1.
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Weight: 0.668 lbs per linear foot (0.996 kg/m), calculated using the formula:
Weight=Diameter2×0.00617
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Cross-Sectional Area: 0.20 square inches (129 mm²), critical for load-bearing calculations.
Material and Grade
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Grade: Typically ASTM A615 Grade 60, with a yield strength of 60,000 psi (414 MPa). This ensures compliance with seismic and structural requirements in residential and light commercial projects.
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Surface: Deformed ribs for superior bonding with concrete, reducing slippage risks.
Applications in Construction
1. Residential Foundations and Slabs
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Grid Spacing: 12–18 inches for driveways and floor slabs to resist cracking from thermal expansion.
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Frost Walls: Prevents structural damage in cold climates by maintaining tensile strength during freeze-thaw cycles.
2. Retaining Walls and Light Commercial Structures
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Horizontal Reinforcement: Spaced 6–12 inches apart to counteract soil pressure in walls up to 10 feet tall.
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Beam-Column Joints: Enhances ductility in seismic zones when paired with Grade 60 specifications.
3. Precast Concrete Components
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Modular Efficiency: Compatible with automated rebar-tying machines, reducing labor costs by 25% in prefabricated beams and panels.
Best Practices for Installation
Spacing and Concrete Cover
| Application | Spacing | Concrete Cover |
|---|---|---|
| Residential Slabs | 12–18″ | 2″ (50 mm) |
| Retaining Walls | 6–12″ | 1.5″ (38 mm) |
| Industrial Floors | 6–9″ | 3″ (75 mm) |
Corrosion Prevention
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Epoxy Coating: Mandatory in coastal or high-moisture environments to extend lifespan by 20+ years.
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Cathodic Protection: Used in bridges and wastewater plants for added durability.
Industry Trends (2025)
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BIM Integration: Tools like Revit automate #4 rebar placement in curved walls and complex geometries, minimizing clashes.
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Sustainable Practices: Recycled steel variants with 95% post-consumer content align with LEED certification goals.
FAQs
Q: Can #4 rebar replace welded wire mesh in slabs?
A: Yes—#4 rebar grids provide superior crack control for heavy loads, while mesh suits lighter applications like sidewalks.
Q: How does #4 rebar compare to #5 in cost?
A: #4 is 15–20% cheaper per ton, making it ideal for moderate-load projects.
Q: What is the maximum span for #4 rebar in residential beams?
A: Up to 12 feet with 9-inch spacing, per ACI 318 guidelines.