What to plan before building a retaining wall
Plan wall height, geogrid reinforcement, drainage, excavation, and access before ordering retaining-wall materials.
Record what the wall needs to hold back
Start on the satellite map: use Distance for each straight section of the proposed wall and add Marks for access, drains, or obstacles. Then record the height changes on site. Wall length and retained height answer different questions.
This guide covers planning for segmental concrete-block retaining walls. Before choosing blocks, answer these questions:
- Where is the wall tallest? Record exposed height along the run, not just an average. Distinguish the visible face from the full structure, including buried blocks.
- What is above and below it? Note slopes, parked vehicles, buildings, fences, and other walls. Loads and nearby tiers can affect the design.
- Where does water go now? Mark downspouts, irrigation, wet ground, and runoff paths before the wall changes them.
- What space is available? Allow for excavation behind the face, material staging, and equipment—not just the finished block footprint.
The blocks are only part of the order
Budget for the supporting materials alongside the face blocks. Ask the block supplier or designer to identify the required base, backfill, drainage, and reinforcement for your site.
| Order item | Question to resolve |
|---|---|
| Blocks and caps | Which block system, face dimensions, corners, curves, buried courses, and cap lengths are in the design? |
| Compacted base | What aggregate, width, depth, and compaction does that system require? |
| Drainage stone and pipe | What goes behind the wall, and where does collected water discharge? |
| Backfill and reinforcement | Can the excavated soil be reused? Is geogrid required, and how much room does it need? |
| Excavation and handling | How will excess soil leave, deliveries arrive, and equipment reach the work? |
When does a retaining wall need geogrid?
Use geogrid when the chosen wall system and site design require reinforced soil behind the blocks. Taller walls are more likely to need it, but soil, slopes, nearby tiers, and loads such as a driveway can make it necessary on a shorter wall too. Check the block system’s design limits rather than using height alone.
Geogrid is a strong open mesh laid between selected block courses and extended back into compacted fill. It helps the blocks and reinforced soil act together. It is not landscape fabric, and it does not replace drainage stone or a water outlet.
Get the grid type, strength, direction, layer positions, and length behind the wall from the design before ordering. That length determines how far you must excavate. A fence, property line, or buried utility behind the wall can change what is feasible; grid cannot simply be shortened to fit.
Give water an outlet
Drainage stone behind the wall and a pipe near its base are common parts of a system, but a pipe needs a planned outlet. Confirm where it discharges and how that outlet stays open. Do not direct water onto a neighboring property or leave the destination undecided.
Surface runoff needs its own plan. Roof water and water flowing down a slope should not simply be sent into the wall’s drainage zone. Show those sources to the designer so grading and drainage work together.
Check design and permit requirements before buying
A short wall is not automatically a simple wall. Height, soil, slopes, water, and loads all matter. Ask your local building department how it measures wall height and when a permit or engineered design is required. There is no nationwide height cutoff that clears every site.
Tell the supplier about every nearby load and tier. A wall beside a driveway, a steep slope, or another wall may need a different design from a freestanding garden border of the same visible height. Have a qualified wall designer resolve those conditions before you select reinforcement or start excavation.
In the U.S., contact 811 before digging, wait for the required responses, and follow your state’s safe-digging process. Privately installed irrigation, lighting, or other lines may need a separate locator. Confirm property boundaries, easements, and drainage permissions as part of the site review.
Use the design to build the material list
Use the retaining-wall calculator with your wall length, exposed height, and selected block dimensions. Review the buried-course and material assumptions against the supplier’s design rather than entering the full height as visible height.
For a stepped or changing-height wall, break the run into sections with their own heights. Ask the supplier to reconcile corners, curves, step-ups, cuts, and complete pack quantities before placing the order.
Example supplier brief: “A 20-foot run with about 2 feet of exposed wall at its tallest point, a driveway above it, and a narrow equipment-access route. Please confirm the full wall height, reinforcement, excavation behind the face, drainage outlet, and quantities for the selected blocks.” Those details are more useful than asking for a price on 40 square feet of blocks.
Compare the complete work: excavation, soil haul-off, base and compaction, drainage, any reinforced fill, blocks and caps, delivery access, and repair of the surrounding lawn. Ask where pallets can be unloaded and whether the equipment can reach that location. Handling material by wheelbarrow through a narrow gate is a different job from placing pallets next to the wall.
Bring the satellite layout, height notes, site photos, and material estimate to that conversation. Reserve the work dates after design, utility locating, deliveries, and disposal are arranged—not just when the blocks are available.