A well-built gravel driveway can last decades with proper materials and installation. This guide helps you choose the right gravel for your mountain property.

Understanding Gravel Types

Different gravel types serve different purposes:

Base Course (Road Base)

Composition: Mix of ¾" rock, sand, and fines

Purpose: Primary structural layer

Depth: 4-6 inches compacted

Best For: Foundation stability

Drain Rock

Composition: Clean angular rock, no fines

Purpose: Water drainage

Depth: 2-4 inches when needed

Best For: Wet or spring-prone areas

Top Course (Driveway Gravel)

Composition: Smaller aggregate with fines

Purpose: Driving surface

Depth: 2-3 inches

Best For: Smooth, stable surface

Sizing Matters

Choose appropriate rock sizes:

Large Base Rock (3-4")

Provides structural support

Prevents subgrade penetration

Not suitable for driving surface

Medium Base (¾"-1½")

Good base course material

Compacts well

Provides stability

Surface Course (⅜"-¾")

Comfortable driving surface

Locks together when compacted

Contains fines for binding

Angular vs. Rounded

Rock shape affects performance:

Angular Rock (Crushed)

Locks together firmly

Resists displacement

Better for steep grades

**Recommended for driveways**

Rounded Rock (Pea Gravel)

Rolls and displaces easily

Poor for driveways

Good for decorative use only

Local Materials

Consider regional availability:

Basalt (Dark Gray/Black)

Very hard and durable

Excellent for high-traffic areas

Common in Pacific Northwest

Good angularity

Granite (Light Gray/Pink)

Extremely hard

Excellent durability

Less common, may cost more

Superior performance

Quartzite

Very hard and durable

Often white or light colored

Good drainage

Less available regionally

Driveway Construction Layers

Proper layer sequence:

Layer 1: Subgrade Preparation

Remove topsoil and organics

Grade for proper drainage

Compact native material

Address soft spots

Layer 2: Geotextile (Optional)

Use on soft or wet soils

Prevents mixing of layers

Improves long-term stability

Adds minimal cost

Layer 3: Base Course

4-6" of road base

Compact in 2-3 lifts

Grade for crown drainage

Most critical layer

Layer 4: Surface Course

2-3" of top course gravel

Compact thoroughly

Maintain proper crown

Refresh as needed

Drainage Considerations

Critical for mountain driveways:

Crown Shape

Center 2-3" higher than edges

Promotes water runoff

Prevents standing water

Essential for longevity

Cross Culverts

Install every 200-400 feet

Larger for steeper terrain

Protect with headwalls

Keep clear of debris

Roadside Ditches

Grade for positive drainage

Size for peak flow

Armor with rock if needed

Maintain regularly

Steep Grade Solutions

Special considerations for steep driveways:

Grade Dips

Install water bars

Space every 50-100 feet

Angle across road

Outlet to stable area

Surface Binding

Add polymer stabilizers

Consider chip seal

Use larger surface rock

Compact extra thoroughly

Switchbacks

Design with adequate radius

Build retaining walls if needed

Ensure good compaction

Plan for snow removal

Quantity Calculations

Estimate material needs:

**Formula**: Length × Width × Depth ÷ 27 = Cubic Yards

**Example**: 200' × 12' × 0.5' ÷ 27 = 44.4 cubic yards

**Rule of Thumb**:

Base course: 3-4 yards per 100 feet (12' wide)

Surface course: 1-2 yards per 100 feet

Cost Breakdown

Typical costs per cubic yard:

Base course rock: $25-$45

Drain rock: $30-$50

Surface course: $30-$50

Delivery: $100-$200

Spreading & compaction: $50-$100/yard

**Total**: $2,000-$8,000 for 300' driveway

Maintenance

Keep your driveway in top condition:

Spring

Fill potholes and ruts

Regrade drainage

Add fresh surface material

Compact repairs

Summer

Control dust with water or additives

Maintain crown shape

Clear vegetation

Address erosion

Fall

Add gravel before winter

Clear culverts and ditches

Repair summer damage

Prepare for plowing

Winter

Plow carefully to preserve surface

Sand icy spots (avoid salt)

Remove berms

Minimize traffic when thawing

Common Mistakes to Avoid

Don't make these errors:

**Insufficient base**: Leads to early failure

**Wrong rock type**: Pea gravel doesn't work

**Poor drainage**: Water destroys driveways

**No compaction**: Loose rock shifts

**Too thin**: Inadequate layer depth

When to Hire Professionals

Consider professional installation for:

Driveways over 300 feet

Steep grades (>10%)

Poor soil conditions

Significant drainage issues

Retaining walls needed

Conclusion

A properly built gravel driveway provides reliable access for decades. Choose the right materials, follow proven construction methods, and maintain regularly for best results.

We specialize in mountain driveway construction throughout the Inland Northwest, from material selection through final grading.

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