How to Lay Pavers Over Existing Concrete

The project starts with a thorough assessment of the existing slab, followed by careful preparation to ensure a durable, attractive result. This guide covers two common methods for laying pavers over concrete: a mortar bed or a dry-set/pedestal system. Each method has specific steps, materials, and considerations to improve longevity, drainage, and curb appeal for a US audience.

Preparation And Assessment

Inspect the concrete for cracks, spalling, or excessive moisture. Resolve any structural issues before proceeding. Clean the surface thoroughly to remove debris, oil, and grease. If the slab is not level, plan to address high spots and depressions so the paver surface remains even. Determine drainage direction and ensure water will shed away from structures. Verify local code requirements for paver installations, edge restraints, and sublayer materials.

Choose A Laying Method

There are two primary approaches when laying pavers over concrete. The mortar-bed method uses a thin cementitious setting bed that bonds to the slab and supports pavers. The pedestal or dry-set method creates a raised, ventilated deck over the concrete with plastic or metal pedestals and a sand-filled grid. The pedestal method is favored when drainage, future access to utilities, or roofline clearance matters, while the mortar-bed method offers a tighter, lower-profile finish.

Mortar-Bed Laying Method (Bonded Setting Bed)

This method creates a solid, bonded surface between pavers and the concrete. It is best for flat, low-traffic areas where a seamless look is desired. A bonding mortar or cementitious leveling underlayment is applied to the prepared concrete, then pavers are set and grouted with polymeric sand or a compatible mortar.

Materials And Tools

• Bonding mortar or cementitious leveling underlayment
• Portland cement, sand, and water for custom mixes (per product guidelines)
• Pavers or flagstones
• Polymeric sand (for joints) or standard joint sand plus sealing material
• Edging restraints, spacers, levels, and rubber mallet
• Water, buckets, mixing container, trowel, screed boards
• Sealant or breathable impregnator (optional)

Step-By-Step

1. Clean and dry the concrete surface; remove curing compounds that hinder bonding.
2. Mix and apply a bonding mortar or leveling bed according to product instructions, forming a flat, smooth surface.
3. Lay pavers in the chosen pattern, using spacers to maintain consistent joint widths.
4. Tap pavers gently with a rubber mallet to seat them evenly; maintain a slight crown for drainage where needed.
5. Fill joints with polymeric sand and compact; mist with water to activate the polymer.
6. Install edge restraints to prevent movement and ensure stability around the perimeter.
7. Seal the surface if the pavers and joint material recommend it for durability and stain resistance.

Dry-Set Or Pedestal System (Raised, Freestanding Approach)

The pedestal method creates a ventilated, accessible pedestal grid above the concrete. This approach is ideal when the area needs water drainage, hidden utilities, or annual maintenance access.

Materials And Tools

• Pedestals or pedestals grid (adjustable height)
• Support framework (stringers or grid panels)
• Pavers or tiles
• Non-woven membrane or drainage layer (optional)
• Joint material (polymeric sand or grout)
• Sealing products (optional)

Step-By-Step

1. Prepare the concrete surface and address any major irregularities; ensure a clean, dry base.
2. Install a drainage layer or membrane if recommended by the system manufacturer.
3. Place pedestals at grid intersections and level them to achieve a uniform walking plane.
4. Lay the support framework and verify alignment and level across the entire area.
5. Position pavers on the pedestals, tapping into place with a rubber MALLET; check for levelness.
6. Fill joints with polymeric sand and compact; dampen as required to activate polymer.
7. Attach edge restraints to maintain stability and prevent lateral movement.
8. Apply optional sealant for color longevity and stain resistance.

Surface Prep And Subsurface Considerations

A flat, clean surface is essential for both methods. For concrete slabs, repair cracks and fill major depressions to avoid telegraphing through pavers. A moisture barrier may be advisable if the slab has moisture issues; consult product guidelines for compatibility with pavers and grouts. If the slab is new, allow adequate curing time before installation. For raised decks, ensure the system chosen accommodates typical temperature expansion and contraction in the US climate.

Drainage, Bedding, And Edge Restraints

Proper drainage prevents standing water and freeze-thaw damage. On bonded installations, ensure a slight slope away from structures. In raised installations, maintain sufficient clearance around doors and walls and ensure the pedestal height accommodates drainage paths. Use edge restraints to lock pavers in place and prevent shifting, particularly in high-traffic areas or spaces exposed to wind and rain.

Maintenance And Long-Term Care

Regular cleaning helps preserve color and reduce staining. Sweep or blow debris; wash with a mild detergent for tough soils. Inspect joints annually and replenish sanding material if gaps appear. Sealants or impregnators may extend color life and staining resistance; follow product guidance regarding cure times and reapplication schedules. Avoid harsh chemicals that could erode joint material or pavers. For raised systems, check pedestal stability and re-level as needed after seasonal movement.

Common Mistakes To Avoid

• Overlooking surface moisture and improper drainage leading to pooling.
• Not addressing structural cracks or heaving in the existing slab.
• Ignoring expansion joints and not providing adequate jointing between pavers.
• Using unsuitable or incompatible mortar, sand, or sealants that hinder movement or adhesion.

Edge Details And Expansion Gaps

Edge restraints must be installed along all sides to prevent lateral movement; maintain expansion gaps where the pavers meet fixed structures or change in plane. Use consistent joint widths, typically 1/4 inch to 1/2 inch, depending on paver size and joint material. Consider backer rods or perimeter trims to accommodate thermal expansion and contraction in varied climates.

Cost Considerations

Costs vary by material, method, and area. A bonded setting bed generally requires more concrete and bonding materials but can deliver a seamless look. A pedestal system has higher material costs per square foot but offers drainage, easier under-slab access, and a cleaner finish. Budget for sublayer materials, pavers, edge restraints, jointing materials, labor, and potential permits or inspections.

What To Ask A Contractor

• Which laying method do you recommend for my area and why?
• How will you ensure proper drainage and slope?
• What are the expected maintenance needs and life span?
• Do you use approved adhesives, mortars, and joint materials?

Quick Reference: Pros And Cons