Steps To Install A Retaining Wall For Delaware Properties

Retaining walls are practical, attractive features that control erosion, create usable terraces, and protect structures on sloped Delaware lots. Installing a retaining wall correctly requires an understanding of local site conditions, suitable materials, proper drainage, and adherence to local codes. This guide provides detailed, practical steps and professional best practices tailored to Delaware properties so you can plan, permit, and construct a durable wall.

Why a Retaining Wall May Be Necessary in Delaware

Delaware’s coastal plain soils, varied groundwater levels, and occasional heavy rain events make retaining walls a common solution for landscaping and erosion control. Whether you are stabilizing a driveway approach, creating a raised plantingbed, or protecting a foundation, a properly built wall prevents soil movement, reduces sediment runoff, and adds usable, level space.
Common reasons Delaware homeowners install retaining walls include:

managing sloping lots during new construction or grading projects
preventing erosion near coastal or riverfront properties
creating terraces for gardens and patios
protecting foundations, septic fields, and driveways from runoff damage

Local Regulations and Permits

Before you break ground, check with your county building department and local municipal planning office. Delaware municipalities and counties (New Castle, Kent, and Sussex) may have different permit triggers and setbacks for retaining walls.

When a permit is typically required

Walls higher than a specified height (commonly 3 to 4 feet measured from the bottom of the footing to the top of the wall) frequently require a building permit and engineered plans.
Walls supporting structures, bearing a surcharge (like a driveway or a building), or located near property lines or easements usually require engineering review.
Walls seaward of coastal hazard or wetland buffers may be restricted or require environmental approval.

Always obtain written confirmation of permit requirements and submit plans if required. Failure to permit can lead to removal orders or costly retrofits.

When to call a professional engineer

If the wall will retain more than about 4 feet of soil.
If the wall supports a roadway, driveway, or heavy dead load.
If the site has high groundwater, steep slopes above the wall, or undermining concerns.

Hiring a licensed civil or geotechnical engineer ensures safer design and smoother permitting.

Materials and Designs Suitable for Delaware Climate

Delaware’s climate–humid, with occasional freeze-thaw–calls for durable materials and good drainage. Material choice depends on wall height, aesthetic goals, and budget.

Concrete block (segmental retaining wall blocks): Durable and modular; block systems often include lip features and allow for geogrid reinforcement. Good for 2-12+ foot walls depending on reinforcement.
Natural stone: Attractive, long-lived, and heavy; requires skilled installation and often a reinforced foundation for taller walls.
Timber: Economical for short walls (under 3-4 feet), but susceptible to rot unless pressure-treated or capped with stone.
Poured concrete: Strong and versatile for engineered walls, especially close to structures or where water loads are expected.
Gabion baskets: Wire baskets filled with stone; flexible, permeable, and suitable for erosion-prone sites.

Choose frost-resistant materials and finishes; verify manufacturer specifications for freeze-thaw durability.

Tools, Materials, and Typical Quantities

Prepare a list of tools and materials before starting. Quantities vary by wall length, height, and block type–calculate volumes using basic geometry and include wastage.

Common tools: shovel, wheelbarrow, plate compactor, level, string line, measuring tape, masonry saw (or block splitter), rubber mallet, tamper, wheelbarrow, landscape fabric.
Drainage materials: 4-inch perforated drain pipe (schedule 40 or corrugated), landscape fabric, 3/4-inch clean crushed stone for drain trench, crushed stone for base (size 3/4″ to 1-1/2″).
Base materials: Angular crushed stone or crusher run for the leveling pad, typically compacted to a stable layer.
Reinforcement: Geogrid (when required for taller or reinforced walls), backfill gravel for compaction.
Wall materials: Segmental retaining wall blocks, capstones, or other chosen facing material.

Step-by-Step Installation Process

The following steps outline a typical installation for a segmental/block retaining wall suitable for many Delaware residential conditions. Adjust dimensions and reinforcement based on wall height and engineer recommendations.

Plan and permit.
Mark the wall alignment with string lines and stakes.
Obtain any required permits and confirm property lines.
Identify underground utilities before digging.
Excavate.
Excavate to the full width of the wall base plus working space. For small modular walls (up to about 3 feet), plan a base trench 6-12 inches deeper than the block height to allow for a compacted crushed-stone base.
Make the base trench at least 6-12 inches wider than the block on each side to enable compaction and a batter where required.
For walls supporting heavy loads or over 4 feet, excavation must reach design depths required by engineered plans, often to frost depth or to a compacted structural base.
Prepare the base.
Place 4-6 inches of compactible crushed stone (3/4″ minus or crusher run) for small walls; compact in 2-3 inch lifts with a plate compactor until the base is firm and level.
For larger walls, the base may require deeper engineered stone and a concrete footing; follow plans.
Layout and first course.
Lay the first row of blocks into the compacted base. Level front to back and side to side–this first course controls the alignment of the entire wall.
Use a string level and check corners. Keep blocks tight and maintain a consistent setback (batter) per manufacturer guidance.
Install drainage behind the wall.
Immediately behind the rear of the first course, place a minimum 6-12 inch layer of free-draining clean stone (3/4-inch crushed stone). Compact lightly by hand–do not over-compact against the block faces.
Install a 4-inch perforated drain pipe at the base, wrapped in fabric, sloped to a suitable outlet (storm drain, daylight point, or drywell). The top of the pipe should be placed within the gravel zone to collect groundwater.
Backfill and compaction.
Backfill the gravel zone directly behind the block with 3/4-inch clean crushed stone to allow water to flow to the drain pipe.
Above the drainage zone, use well-graded engineered fill or native soil placed in lifts no more than 6-8 inches thick and compacted to 90-95% standard Proctor density when possible. Use a plate compactor for compaction, keeping it at least 12 inches away from the wall face to avoid disturbing block alignment.
Reinforcement (if required).
For walls taller than the gravity limits, or supporting loads, install geogrid layers following the manufacturer’s specifications and engineer spacing. Typically, geogrid layers are spaced vertically at 6-24 inches on center and extend into the retained soil distance specified by the design (often 2/3 of wall height).
Build additional courses.
Stagger block joints and maintain setback as you stack. Check level frequently.
Cut blocks as needed for corners and ends using a masonry saw or block splitter.
Capstones and finishing.
Install capstones with construction adhesive designed for masonry to protect the wall from water infiltration and to provide a finished look.
Place landscaping fabric over the finished backfill, add topsoil as needed, and seed or plant for erosion control on slopes above the wall.
Final grading and maintenance planning.
Grade the slope above and below the wall to divert surface water away from the wall face.
Plan periodic inspections, especially after heavy rains or freeze-thaw cycles, to check for settlement, bulging, or clogged drains.

Practical Construction Notes and Best Practices

Slope and surface water: Ensure that surface runoff is diverted away from the wall. Concentrated flows along the wall face can overwhelm drainage systems.
Drainage is critical: Most failures are caused by poor drainage and hydrostatic pressure build-up. Always include an adequate stone drainage zone and outlet for the perforated pipe.
Compaction: Proper compaction of the foundation and backfill is as important as the wall material. Soft or uncompacted soils will lead to settling and leaning.
Frost considerations: Delaware experiences freeze-thaw cycles; design base depths and use frost-resistant materials. For engineered walls, footings may need to extend below the local frost depth–verify with a local engineer or code official.
Planting near walls: Use shallow-rooted plants for terraces immediately behind low walls. Avoid planting large trees too close to retaining walls because root growth and tree loads can compromise the structure.

Estimating Costs and Timeline

Costs vary widely by material, wall height, site access, and whether you hire a contractor. As a rough guide:

Small, DIY timber or block walls (under 3 feet): lower material costs and a weekend or two of labor.
Segmental block walls with moderate length and up to 4 feet of height: moderate cost; expect several days to a couple of weeks including excavation, drainage, and curing where needed.
Engineered poured concrete or tall reinforced walls: highest cost, may take several weeks including permitting and curing.

Obtain multiple estimates and compare not just price but scope–check that pricing includes proper drainage and base preparation.

Final Checklist Before Closing

Confirm permits are issued and inspections scheduled.
Verify drain outlets are functional and not directed toward neighboring properties or wetlands.
Ensure manufacturer instructions and engineer details (if used) were followed for base depth, grid placement, and compaction.
Schedule a final inspection after the first major rain event to ensure no visible seepage or settlement.

A correctly designed and constructed retaining wall protects your Delaware property for decades. Prioritizing drainage, compaction, and code compliance reduces risk and future maintenance, while choosing the appropriate materials ensures the wall complements both function and curb appeal.