Why Reinforce Concrete?
Concrete is strong in compression but weak in tension. When forces pull or bend concrete, it cracks. Reinforcement:
- Holds cracks together
- Distributes load across larger areas
- Prevents catastrophic failure
- Allows thinner slabs in some applications
Important: Reinforcement doesn’t prevent cracks—it controls them.
Rebar vs. Wire Mesh: Quick Comparison
| Factor | Rebar | Wire Mesh |
|---|---|---|
| Strength | Higher | Moderate |
| Cost | Higher | Lower |
| Installation | More labor | Easier |
| Best for | Structural, driveways | Patios, sidewalks |
| Crack control | Better | Good |
| Placement | More precise | Can shift during pour |
Understanding Wire Mesh
Types of Wire Mesh
Welded Wire Fabric (WWF)
- Most common type
- Wires welded at intersections
- Sold in flat sheets or rolls
- Designated by wire spacing and gauge
Common designations:
- 6×6 W1.4/W1.4 (6” squares, light gauge)
- 6×6 W2.9/W2.9 (6” squares, heavier gauge)
- 4×4 W4/W4 (4” squares, heavy gauge)
When to Use Wire Mesh
Ideal applications:
- Patios and walkways
- Shed floors
- Light-duty garage floors
- Basement floors (non-structural)
- Pool decks
Not recommended for:
- Driveways with heavy vehicles
- Structural slabs
- Foundation walls
- Areas with soil movement
Wire Mesh Installation
Proper placement:
- Position mesh in middle to upper third of slab
- Use concrete chairs or dobies to elevate
- Overlap sheets minimum 6 inches
- Tie overlaps with wire
- Keep mesh 2 inches from edges
Common mistake: Laying mesh on ground and “pulling up” during pour. This rarely positions mesh correctly and often results in mesh at bottom of slab where it does nothing.
Wire Mesh Costs
| Type | Cost per Sheet (5’×10’) | Coverage |
|---|---|---|
| 6×6 W1.4 | $8-12 | 50 sq ft |
| 6×6 W2.9 | $15-25 | 50 sq ft |
| 4×4 W4 | $25-40 | 50 sq ft |
Per square foot: $0.15-$0.75
Understanding Rebar
Types of Rebar
Designation by size:
- #3 (3/8” diameter)
- #4 (1/2” diameter)
- #5 (5/8” diameter)
- #6 (3/4” diameter)
Material types:
- Carbon steel (most common)
- Epoxy-coated (corrosion resistant)
- Galvanized (salt environments)
- Stainless steel (marine/chemical exposure)
- Fiber-reinforced polymer (FRP)
When to Use Rebar
Ideal applications:
- Driveways
- Garage floors
- Structural slabs
- Foundation walls
- Retaining walls
- Any engineered application
Overkill for:
- Small patios
- Interior sidewalks
- Light shed floors
Rebar Grid Patterns
Common spacing:
- 12” on center (residential slabs)
- 18” on center (light-duty)
- 6” on center (structural)
Grid patterns:
- Single layer (#3 or #4 at 12” OC)
- Double layer (top and bottom for thick slabs)
Rebar Installation
Steps:
- Lay out grid pattern on chairs
- Tie intersections with wire ties
- Maintain 2-3” concrete coverage (all sides)
- Check placement before pour
Tying technique:
- Use 16-gauge tie wire
- Simple wrap and twist at intersections
- Not every intersection needs tying (every other is often sufficient)
Rebar Costs
| Size | Cost per 20’ Length | Per Linear Foot |
|---|---|---|
| #3 (3/8”) | $6-10 | $0.30-$0.50 |
| #4 (1/2”) | $10-15 | $0.50-$0.75 |
| #5 (5/8”) | $15-22 | $0.75-$1.10 |
| #6 (3/4”) | $22-32 | $1.10-$1.60 |
Fiber Reinforcement: The Third Option
What Is Fiber Reinforcement?
Synthetic or steel fibers mixed directly into concrete. Types include:
- Polypropylene (plastic fibers)
- Steel fibers
- Glass fibers
- Natural fibers (experimental)
Pros and Cons
Advantages:
- No placement issues
- Distributes throughout entire slab
- Reduces plastic shrinkage cracking
- Speeds installation
- No corrosion
Limitations:
- Doesn’t replace structural reinforcement
- Can affect surface finish
- Steel fibers may rust if exposed
- Variable effectiveness
When Fiber Works
Good for:
- Controlling plastic shrinkage cracks
- Adding to mesh-reinforced slabs
- Sidewalks and patios
- Industrial floors (with steel fibers)
Not a substitute for:
- Rebar in structural applications
- Wire mesh in load-bearing slabs
Placement Depth: The Critical Factor
The “Cover” Rule
Reinforcement must have adequate concrete cover:
| Application | Minimum Cover |
|---|---|
| Interior floors | 3/4” |
| Exterior exposed | 1.5” |
| Ground contact | 3” |
| Severe exposure | 2-3” |
Why Depth Matters
- Too high: Surface cracking, spalling
- Too low: Corrosion, no tension resistance
- Bottom of slab: Provides zero benefit
Target zone: Middle to upper third for flatwork
Choosing the Right Reinforcement
Decision Matrix
Use wire mesh (6×6) when:
- Slab is 4” thick
- Light foot traffic only
- No vehicle loads
- Budget is limited
- Soil is stable
Use rebar (#3 or #4 at 12” OC) when:
- Slab receives vehicle traffic
- Slab is 5” or thicker
- Soil has expansion potential
- Cracking is a major concern
- Project requires engineering
Use both when:
- Heavy loads expected
- Soil conditions poor
- Maximum crack control needed
- Engineer specifies
Application Guide
| Project | Recommended Reinforcement |
|---|---|
| Patio | 6×6 mesh or fiber |
| Sidewalk | 6×6 mesh or fiber |
| Driveway | #3 rebar at 18” OC |
| Garage floor | #3 rebar at 18” OC |
| Foundation | Per engineer (usually #4-#5) |
| Retaining wall | Per engineer |
Common Reinforcement Mistakes
Mistake 1: Mesh on the Ground
Problem: Stepping on mesh during pour pushes it to bottom
Fix: Use proper chairs, walk on planks, place mesh as you pour
Mistake 2: Insufficient Overlap
Problem: Mesh sheets not connected properly
Fix: Minimum 6” overlap, tied with wire
Mistake 3: Skipping Chairs/Dobies
Problem: Reinforcement sinks during pour
Fix: Always use support chairs at 2-foot intervals
Mistake 4: Rusty Rebar
Problem: Loose scale rust affects bond
Fix: Clean loose rust, light surface rust is acceptable
Mistake 5: Wrong Size for Application
Problem: Using mesh where rebar needed (or vice versa)
Fix: Match reinforcement to load requirements
Support Chairs and Dobies
Types
- Plastic chairs (most common)
- Wire chairs
- Concrete dobies
- Precast spacers
Spacing
- Every 2-3 feet for mesh
- Every 3-4 feet for rebar
- More support near edges
Height Selection
| Slab Thickness | Chair Height |
|---|---|
| 4” | 1.5” (mesh at center) |
| 5” | 2” |
| 6” | 2-2.5” |
Code Requirements
Most residential concrete doesn’t require reinforcement by code, but it’s strongly recommended. Check local codes for:
- Minimum slab thickness
- Reinforcement requirements for garages
- Foundation specifications
- Driveway requirements
When in doubt: Contact your local building department.
Calculate Your Concrete Project
Ready to plan your reinforced concrete project? Use our free Concrete Calculator to estimate quantities and costs.
Pro Tip: For DIY projects, use chairs generously—they’re cheap insurance against improper placement. Consider fiber reinforcement as a supplement (not replacement) to mesh or rebar for maximum crack resistance. And remember: reinforcement does nothing if it’s sitting at the bottom of the slab.