Hardscape Construction: Pavers, Retaining Walls & Stone

Welcome

Hello, and welcome. This is Super Structures General Contractors — a national general contractor headquartered in Powhatan, Virginia — here to help you and your clients build something that lasts. We're glad you're with us, and we look forward to connecting with you.

Alright, Hardscape Construction: Pavers, Retaining Walls & Stone. Don't let the plain title fool you. Here's the part that actually matters on the job: Hardscape lasts as long as what's under it — excavate to depth, build a compacted base, restrain the edges, drain behind walls, and know when a retaining wall needs an engineer and a permit. Learn it well and your patios stay flat and your walls stay standing.

Paver patios and walkways

The industry reference is the CMHA Tech Specs from the Concrete Masonry & Hardscapes Association, formed in 2023 when ICPI and NCMA merged. The sequence:

1. Layout and excavation — dig to the full depth of base plus bedding plus paver, with the subgrade sloped like the finished surface. Compact the subgrade and place geotextile over weak or clay soils.
2. Base — crushed, dense-graded aggregate (specs often cite ASTM D2940), typically 4 to 6 inches compacted for patios and walks and 8 to 12 inches or more for driveways, placed and compacted in 3- to 4-inch lifts, extending about 6 inches beyond the paver edge to carry the edge restraint.
3. Bedding — 1 inch of concrete sand (ASTM C33), screeded to grade and never walked on. Not stone dust, not screenings.
4. Pavers — concrete pavers meet ASTM C936; set them in pattern, cut with a wet saw, and keep joints consistent.
5. Edge restraint — plastic, aluminum, or concrete at every unsupported edge, spiked into the base; without it the field spreads and fails.
6. Compaction and joints — compact the pavers with a plate compactor (padded on textured units), sweep in joint sand or polymeric sand, compact again, and activate polymeric sand with water exactly per the manufacturer. Surface slope: a minimum of about 1 percent, 2 percent preferred, away from structures.

Segmental retaining walls

Dry-stacked SRW units (ASTM C1372) rely on mass, setback, and soil reinforcement:

• Leveling pad — 6 inches of compacted aggregate, extending in front of and behind the block.
• Buried base course — roughly 1 inch for every 8 inches of wall height, 6 inches minimum.
• Batter — the setback built into each course that leans the wall into the soil.
• Drainage — 12 inches of clean, open-graded stone behind the units, a perforated drain pipe at the base daylighted to an outlet, and geotextile between stone and soil.
• Geogrid — layers of reinforcement extending back into compacted fill as the design requires on taller walls and on any wall with a surcharge.
• Compaction behind the wall in lifts, with only hand-operated equipment within 3 feet of the units.

When an engineer and permit are required: the IRC (R105.2) and IBC (105.2) exempt from permits retaining walls not over 4 feet measured from the bottom of the footing to the top of the wall, unless the wall supports a surcharge (a slope, driveway, structure, or another wall above) or impounds liquids. Anything taller, surcharged, or closely tiered needs engineered drawings, a permit, and usually inspections; local rules are sometimes stricter. Walls are designed under IBC 1807.2 and the CMHA (formerly NCMA) design manual for SRWs.

Concrete and natural stone

Exterior concrete flatwork is typically 4 inches thick on compacted base, with control joints spaced per ACI guidance (roughly 2 to 3 times the thickness in feet, so 8 to 12 feet for a 4-inch slab) and air-entrained mix in freeze-thaw climates. Natural stone is laid two ways: dry-laid flagstone on a compacted base and bedding like pavers, or wet-laid in mortar on a reinforced concrete slab. Mortared stone on a bare aggregate base cracks the first winter.

Outdoor structures in general

Pergolas, decks (IRC R507), outdoor kitchens, fire features, fences, and pool surrounds each carry their own code, permit, and setback rules. Gas, electrical, and plumbing for an outdoor kitchen are licensed-trade work. Fire pits have clearance rules under the fire code and local ordinances; pool barriers follow the ISPSC or the IRC. Zoning controls fence height and anything built in a setback or easement.

Going Deeper (Intermediate)

Permeable interlocking concrete pavement (PICP) uses open-graded stone layers (No. 57, No. 2, No. 8) instead of dense base and sand so water infiltrates; it is a stormwater device built to the engineer's section. Steps are built like small retaining walls with a consistent riser. Commercial walks must meet accessibility requirements — running slope no more than 1:20 and cross slope no more than 1:48 on an accessible route. Efflorescence, the white haze on new pavers, is normal and weathers off.

Advanced / Pro-Level

Pros see surcharge everywhere a customer doesn't: a parked truck, a slope above, a fence post line, a pool, a second wall closer than about twice the lower wall's height. They design drainage before block: where the pipe daylights, how the wall drains if the pipe clogs, and where roof water behind it goes. They check utility conflicts in the reinforced zone before ordering geogrid. On engineered walls they schedule the engineer's inspections of pad, drainage, grid, and backfill, and keep the compaction reports in the job file.

Practice Challenge

A homeowner wants a 5-foot wall to level a backyard, with a new paver patio on the fill behind it, and the hardscape crew says they've built hundreds "without a permit." What's wrong? (Answer: the wall is over 4 feet from the bottom of the footing and supports a surcharge (the fill and patio), so it requires an engineer's design and a permit under IRC R105.2; it also needs geogrid, drainage, and compacted structural fill, and an unpermitted failure lands on the contractor.)

In Practice

A crew that excavates to depth, compacts in lifts, sets edge restraint, and drains behind the wall builds patios that are flat ten years later. A crew that sets pavers on 2 inches of stone dust and stacks block on dirt is back for warranty work in two springs.

Common Mistakes to Avoid

• Thin or uncompacted base and stone dust bedding
• No edge restraint, or restraint sitting on bedding sand instead of base
• Walls over 4 feet or carrying a surcharge built without an engineer or permit
• No drainage stone or drain pipe behind a wall

Takeaway: Hardscape lasts as long as what's under it — excavate to depth, build a compacted base, restrain the edges, drain behind walls, and know when a retaining wall needs an engineer and a permit.

Educational overview only — not hands-on landscape or hardscape training, an engineered design, a safety program, or licensing advice. Follow OSHA, the IRC/IBC and local grading and retaining-wall permit requirements, your state's contractor, irrigation, and pesticide applicator licensing rules, CMHA (ICPI/NCMA) installation guidelines, pesticide labels, and your employer's procedures.