What Is The Base For Pavers? | Solid Base Basics

The Base For Pavers: Layers, Materials, Depths

A paver system rests on a stack of layers that spread load, shed water, and lock units in place. It comes down to order and quality: stable ground, compactable aggregate, a thin bedding layer, tight joints, and firm edging.

Table: Paver Stack At A Glance

Layer	What It Does	Typical Specs
Soil subgrade	Carries everything above it	Excavate to undisturbed soil; compact to a firm, uniform surface; correct soft pockets
Geotextile (as needed)	Keeps soil fines out of the base	Use a separation fabric on clay or mixed soils; overlap seams; extend under edges
Subbase (optional)	Adds thickness over weak soils	4–8 in. of larger crushed stone, compacted in lifts
Base (primary layer)	Provides strength and flatness	4–12 in. of dense-graded 3/4 in. minus or open-graded No. 57 stone, compacted well
Bedding layer	Sets pavers true to line	About 1 in. of washed concrete sand (ASTM C33) or No. 8 stone for open-graded builds
Pavers	The wearing surface	Laid tight; pattern of choice; maintain straight lines
Jointing material	Locks units; resists weeds	Sweep in clean, dry sand or polymeric sand; vibrate to settle
Edge restraint	Stops lateral creep	Spike-in plastic, concrete curb, or aluminum; anchor on the base, not in the sand

Overview Of Materials

Dense-graded base is the classic pick for patios and driveways. It is a mix of crushed stone with fines that compacts into a stable layer. Open-graded base uses clean, uniformly sized stone for rapid drainage and frost relief. Bedding sand needs to be clean and coarse; avoid stone dust or screenings that hold water and pump under load.

Why These Picks Match Accepted Guides

Interlocking pavement groups publish clear notes on gradations, layer order, and sand quality. You can read the step order, compaction tips, and fabric guidance in ICPI Tech Spec 2, and see bedding gradations and open-graded details in a university guidance set. The links appear later in this guide.

How The Layers Work Together

Subgrade And Soil

Everything starts with the ground. Remove organics and soft fill. Compact to a firm, even base. Wet clays swell, so a separation fabric under the base helps maintain thickness and reduce rutting.

Dense-Graded Base

This layer spreads load and sets the plane. Use 3/4 in. minus crushed stone, also called crusher run or class 2 base. Place in 3–4 in. lifts and compact each lift with a plate compactor until the machine changes tone and footprints vanish. Aim for a flat plane at the right slope; dips will telegraph to the surface.

Open-Graded Base

On sites that need fast drainage, open-graded stone works well. A base of No. 57 over a thicker subbase of larger clear stone creates voids for water and reduces frost heave. Keep the top of the base even and within grade; use a small layer of No. 8 as the bedding for this style.

Bedding Sand

The bedding supports each unit and allows minor height tweaks. Use washed concrete sand that meets the C33 gradation. Screed about 1 in. thick on top of the compacted base. Do not over-thicken this layer and do not compact it before laying; compaction happens after the pavers are down. Skip stone dust; it drains poorly and can make surfaces wavy.

Edge Restraints And Joints

Edging keeps the field tight. Set plastic, aluminum, or concrete curbing on the compacted base, not in the bedding. Spike through every hole on curves and at least every second hole on straight runs. After laying, add joint sand, run the compactor to settle the field, then top up the joints. Dry, clean sand helps lock the pattern and limit weed growth.

Sizing The Base Depth For Pavers

Depth depends on soil strength, climate, and load. Sand over compacted stone is forgiving, but only when the base is thick enough for the site. Use the outline below as a starting point and adjust for poor soils or freeze-thaw cycles.

Step-By-Step: Build A Stable Paver Base

1. 1) Plan And Mark: Confirm finished height, slope, and drainage paths. Mark the area with paint and string lines.
2. Excavation: Remove turf and soil to the design depth: base thickness + 1 in. bedding + paver thickness. Keep a constant depth.
3. Subgrade Prep: Shape the soil to the desired slope, then compact. Add a separation fabric on clay or mixed fill with fines.
4. Subbase (When Needed): Place larger crushed stone in lifts and compact. This relieves pressure on weak soils.
5. Base Placement: Add dense-graded 3/4 in. minus or, for open-graded builds, clean No. 57. Place in thin lifts; compact each pass.
6. Slope Check: Set string lines and use a screed board or level to verify fall of about 1–2%. Water must move away from buildings.
7. Bedding Layer: Screed a uniform 1 in. of washed concrete sand (or No. 8 stone for open-graded). Work off screed rails and do not walk on the layer.
8. Laying Pavers: Start from a straight edge. Maintain tight joints and a consistent pattern. Cut with a saw where needed.
9. Edge Restraints: Anchor edging onto the compacted base with spikes. Backfill outside edges to support them.
10. Jointing And Final Compaction: Sweep in sand, compact the field, refill joints, and do one more pass. Brush off fines.

Drainage And Slope Setup

Standing water shortens life. Pitch patios at about 1/8–1/4 in. per foot away from foundations. Extend downspouts and keep softscape higher than the paver edge so water does not sit against the field. Open-graded builds move water through the base; add an underdrain at the low edge if a confining wall blocks outlet flow.

Moisture And Compaction Tips

Slightly damp base material compacts better than bone-dry stone. If dust rises and the plate skates, mist the lift and compact again. Make a second pass at right angles for uniform density. Keep the bedding dry while laying; wet sand bridges under the plate and leaves waves.

Tools That Save Time

A reversible plate compactor, straight pipes for screeding, and tight string lines speed setup and keep planes true. Keep tools clean daily.

Material Choices And When To Use Them

Dense-graded base fits most patios and walkways over decent soils. Open-graded suits permeable jobs, heavy rain areas, and frost zones. Concrete sand works for nearly all bedding needs. No. 8 bedding pairs with open-graded base when the design calls for clear stone from top to bottom. Polymeric joint sand helps in windy spots or on steep pitches; plain dry sand stays flexible and easy to top up.

Table: Typical Base Thickness By Use

Use	Base Thickness	Notes
Garden path	4 in. on firm soils	Light foot traffic; add 2 in. if clay is present
Patio or walk	6–8 in.	Common pick; bump to 10 in. with freeze-thaw and weak subgrade
Driveway	8–12 in.	Match vehicle weight and soil; use thicker lifts and stricter compaction

Quality Checks Before You Lay

Run a straightedge across the base. Gaps larger than a quarter inch need touch-up. Confirm corners are square by measuring diagonals. Check slope with a string line set to finished height minus paver and bedding thickness.

Common Mistakes To Avoid

• Using stone dust for bedding or base fines that trap water
• Skipping the fabric on clay, letting fines migrate
• Laying on a base that was never compacted in lifts
• Making the bedding thicker than 1 in.
• Forgetting edge restraints or spiking them into sand
• Ignoring slope and downspout discharge
• Compacting wet bedding sand before pavers are down

Care After Install

Keep joint sand topped off during the first season. Blow leaves and sweep grit so outlets and joints stay open. If a corner settles, pull that area, add base, and relay; modular units make small fixes simple.

When To Choose Open-Graded From Top To Bottom

Pick a full clear-stone build when the site has poor surface drainage, a high water table, or many freeze cycles. The stack is No. 2 or larger stone as a subbase, No. 57 as base, and No. 8 as bedding, with a matching clean joint stone. Add an outlet drain or daylight edge.

Quick Specs From Trusted Sources

ICPI Tech Spec 2 outlines base prep, lifts, fabric choices, and compaction sequences for interlocking concrete pavements. A university guidance set from California details open-graded layers, stone sizes such as No. 57 and No. 8, and bedding limits. These two reads match the practices listed here and give project-ready charts.

Final Checks And A Short Checklist

• Is the subgrade firm and shaped to slope?
• Are fabric seams overlapped and edges wrapped where soils are weak?
• Was the base placed in thin lifts and compacted until the plate changed tone?
• Does the base plane match your strings within a quarter inch?
• Is the bedding a true 1 in., clean, and undisturbed?
• Are edges anchored on the base and backfilled?
• Were joints filled, the field compacted, and the surface cleaned?

Answering The Keyword Straight

What is the base for pavers? A compacted layer of crushed stone over a firm subgrade with a thin bedding layer on top, held in place by solid edging. Build that stack with the right gradations and you get strong, flat, and long-lasting work.