How Deep Should the Base Be for a Geogrid Driveway?

On firm subgrade, plan 4–6 in (100–150 mm) of compacted aggregate above the geogrid for cars. On medium/soft soils, use 6–12 in (150–300 mm). Keep minimum 4 in cover over the grid, build in 6–8 in lifts, and add 2–4 in in freeze–thaw zones. Always adjust for load, soil, and drainage.

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Why Base Depth Matters？

U want a driveway that doesn’t rut, pump fines, or heave in winter. The right base depth over a driveway grid (geogrid for driveways) spreads wheel loads, locks aggregate, and cuts base thickness versus a non-reinforced section—often with better performance and lower lifetime cost.

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How Geogrid Reduces Base Thickness？

• Interlock: The gravel grid confines aggregate so it behaves like a stiffer slab.
• Load spread: Wheel loads distribute wider and deeper, reducing subgrade stress.
• Rutting control: Less lateral movement = fewer ruts and potholes.
• Base optimization: Typical base can be reduced ~25–50% vs unreinforced sections (project-specific).

Pro Tip: Never skimp below 4 in compacted cover over the grid. Below that, interlock drops and the grid can telegraph.

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Sizing Chart—Base Depth Above Geogrid

Use this quick guide to pick the compacted aggregate thickness above the geogrid. Assumes well-graded crushed aggregate, 95% compaction, and proper drainage.

Subgrade Condition (CBR)	Passenger Cars	Light Trucks/SUVs	Occasional Delivery Truck	Notes
Firm (≥8 CBR)	4–6 in	6–8 in	8–10 in	Good drainage; minimal fines
Medium (4–8 CBR)	6–8 in	8–10 in	10–12 in	Most residential sites
Soft (2–4 CBR)	8–10 in	10–12 in	12–16 in	Use separator geotextile
Very Soft (<2 CBR)	12–16 in	14–18 in	18–24 in	Consider staged fills or subgrade improvement

Without geogrid, expect +30–50% thicker bases for the same performance.

Cold climates: add 2–4 in for frost and verify drainage.

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Layer Stack

1. Subgrade: Proof-roll; undercut soft spots.
2. Separator geotextile (as needed): Stops fines pumping in silts/clays.
3. Geogrid for driveways: Roll tight, orient per manufacturer.
4. Base aggregate (compacted): 4–12 in per table, placed in 6–8 in lifts.
5. Surface course: 1–2 in fines (e.g., 3/8” minus) or your chosen top aggregate.
6. Edge restraint: Timber, curb, or pinned edging to lock shoulders.

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How to Gravel a Driveway with a Driveway Grid (Step-by-Step)

1. Set grade & drainage
   • Target 1–2% crossfall. Route water away from the drive.
2. Excavate
   • Depth = base (table) + surface course + tolerance. Remove organics.
3. Prepare subgrade
   • Proof-roll. If pumping occurs, undercut/replace or use a separator geotextile.
4. Place geogrid
   • Tension flat, overlap 12–18 in at seams, pin per 1–2 m grid or per spec.
5. First lift of aggregate
   • Place 6–8 in, do not drive directly on bare grid; track over with a thin cushion or place from the edge.
6. Compact
   • Plate compactor or roller to 95%. Moisture-condition if dusty/dry.
7. Build to thickness
   • Repeat lifts to reach chart thickness. Keep crown.
8. Top course & finish
   • 1–2 in fines. Compact. Install edge restraint.

Pro Tip: If U see rut depth >½ in during construction traffic, the base is thin or under-compacted. Add material and re-compact before surfacing.

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Material Specs That Work

• Aggregate: Angular, well-graded crushed stone (e.g., ¾” minus). Avoid rounded pea gravel.
• Separator: Non-woven geotextile for silts/clays; woven for strength where needed.
• Geogrid: Biaxial driveway grid for general load spreading; uniaxial where pullout is directional (rare in driveways).

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Cost & Time Signals

• Geogrid: Typically a small % of total, but can save 25–50% base thickness.
• Aggregate: Biggest line item—depth × area.
• Labor: Saved via fewer import loads and faster compaction.
• Lifecycle: Less maintenance from rutting and washboarding.

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Common Adjustments

• Steep grades (>8%): Add +2 in to base; consider check-berms and tighter edge restraint.
• Clayey sites: Always use a separator geotextile; keep water out with ditches and downspout controls.
• Frequent heavy trucks: Use the “Occasional Delivery Truck” column or step one class up.

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FAQ

How deep should the base be for a geogrid driveway?

Use 4–6 in on firm soils for cars, 6–8 in on medium soils, 8–12 in on soft soils. Add depth for heavier vehicles and frost.

Can U place gravel directly on the driveway grid?

Yes—place a thin cushioning layer first, then build in 6–8 in lifts and compact. Avoid driving on bare grid.

Do U still need geotextile if U use geogrid?

Often yes on silts/clays. The geotextile separates, the geogrid reinforces—different jobs.

What aggregate is best over a gravel grid?

Angular, well-graded crushed stone. Rounded material reduces interlock and rut resistance.

Will geogrid stop potholes?

It reduces rutting and fines pumping, which are pothole precursors. U still need correct drainage and compaction.

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Ready for a Spec-Matched Package?

Tell us soil type (or CBR), driveway size, vehicle loads, climate, and U’ll get a base-thickness recommendation, BOM, and pricing—optimized for your site.

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