Block courses, base, backfill and drainage for a segmental retaining wall.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Never build a retaining wall over a buried utility or property line without checking. Call 811 before digging, and confirm you aren't redirecting water onto a neighbor.
| Posts & Panels | $696–$942 |
| Drainage | $141–$191 |
| Membrane & Fabric | $94–$127 |
| Fasteners & Hardware | $30–$40 |
| Soil & Fill | $25–$34 |
| Total | $986–$1,334 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
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About this calculator
Enter a length and height and you get a complete segmental (interlocking block) wall laid out: the total block and cap count by course, the compacted crushed-stone leveling pad, the drainage stone, perforated pipe and fabric behind the wall, and geogrid reinforcement once the wall gets tall — plus the tools, a cost range and a realistic build time.
It automatically buries a base course and adds geogrid above about 3 feet. Open advanced options to set block size and depth, base depth, caps, separation fabric and waste. Tall walls are engineered structures — above roughly 4 feet, get a stamped design and a permit.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Mark the wall line with stakes and string, and have utilities located before you dig. Plan where water will exit at the low end of the drain pipe.
Excavate a trench wide enough for the block plus 6 inches of base on each side, and deep enough to bury the full first course plus your base-pad depth. Dig into firm, undisturbed soil.
Fill the trench with crushed stone, rake it flat, and compact it with a plate compactor. This is the foundation of the wall — get it level and solid before a single block goes down.
Place the first row of blocks on the pad and level each one front-to-back and side-to-side, tapping with a rubber mallet. Take your time — this buried course determines whether the whole wall is straight.
Lay each course offset from the one below (running bond) with the manufacturer's batter, sweeping debris off the tops as you go so blocks seat fully. Cut end and corner blocks with a masonry saw.
Set the perforated pipe at the base, build a chimney of clean drainage stone right behind the blocks against separation fabric, and backfill in thin lifts — compacting each lift before adding the next.
For taller walls, roll out geogrid on top of the specified courses, extending it back into the compacted soil zone, and pin it before the next course locks it in.
Sweep the top course clean, run a bead of block adhesive, and set the cap blocks. Finish grading so surface water sheds away from the top of the wall, not into it.
Equip the job
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Keep planning
Concrete & Masonry
Answers
It varies by jurisdiction, but the common trigger is 4 feet, measured from the bottom of the buried base block to the top of the wall — cross it and most areas require a permit and a stamped engineered design. Taller walls carry serious load and real failure risk, so even where it's allowed, get a design. Below that, a well-built segmental wall with proper drainage is a solid DIY project.
Everything above the first course inherits its accuracy. A buried base course set on a compacted crushed-stone pad, leveled in both directions, is what keeps the wall straight, stable, and frost-resistant. Pros spend roughly half their time on the base — rushing it is the most common reason walls end up wavy or leaning.
Water building up behind a wall is the number one thing that pushes it over. Build a chimney of clean drainage stone directly behind the blocks, run a perforated drain pipe along the base that daylights to the low end, and wrap the soil side with separation fabric so dirt doesn't clog the stone. The planner includes all of this.
Geogrid is reinforcement that ties the wall back into the soil behind it, and most segmental walls need it above about 3 feet, or sooner in poor soils or with a slope or load above the wall. The planner adds geogrid layers once the wall passes that height — confirm the exact layer spacing and length against your block manufacturer's design tables.