A dry-stack retaining wall holds back soil using nothing but stone weight, friction, and geometry — no mortar, no footing. Done right it outlives mortared walls, because it flexes with frost instead of cracking. Done wrong it bulges in the second spring. Expect a full weekend for a 20 ft run at 2 ft tall, two people minimum, and roughly $25–$45 per face foot in stone plus $150–$400 in base and drainage aggregate. Nearly every failure I have been called out to fix traces back to one of three things: a base that was too thin, drainage stone that was never installed, or a wall built dead-vertical instead of leaning back into the hill.
Tools & Materials
- Crusher run for the compacted base trench
- #57 stone for the drainage chimney behind the wall
- Non-woven filter fabric (separates drainage stone from backfill soil)
- Wall stone — flat-bedded fieldstone, quarried wallstone, or split block
- Hearting stone: small angular chips and spalls for filling voids
- Plate compactor and a hand tamper for the trench
- 4-ft level, torpedo level, mason’s string, and stakes
- Brick hammer, stone chisel, and a 3 lb sledge (safety glasses, always)
- 4 in perforated pipe, if the wall is long or the site holds water
Wall stone is sold by the ton and covers far less than people expect — size the face with the retaining wall calculator or the stone wall calculator, and the base and drainage aggregate separately with the crusher run calculator and the #57 stone calculator. Our breakdown of retaining wall cost covers the full budget including delivery.
| Wall height | Face stone per 10 lf | #57 drainage stone per 10 lf | Base crusher run per 10 lf |
|---|---|---|---|
| 18 in | 0.6 ton | 0.6 yd³ | 0.7 yd³ |
| 24 in | 0.8 ton | 0.7 yd³ | 0.9 yd³ |
| 36 in | 1.2 ton | 1.1 yd³ | 1.6 yd³ |
| 48 in | 1.6 ton | 1.5 yd³ | 2.7 yd³ |
Those figures assume a 12 in thick face, a 12 in drainage column, and the base dimensions below. Order stone 10% long.
Know Your Height Limit Before You Start
Most jurisdictions treat 4 ft — measured from the bottom of the base to the top of the wall, not from finished grade — as the line where a retaining wall stops being landscaping and becomes a structure. Above that you generally need a permit, an engineered design, and often geogrid reinforcement tied into the slope. Certain conditions drop that threshold to 3 ft or even 30 in: a driveway, patio, pool, or structure above the wall; a slope continuing to rise behind it; or a tiered wall sitting within the lower wall’s influence zone.
Critical: A wall over 4 ft tall, or any wall with a driveway or structure loading the soil above it, needs an engineer — not because of code paperwork, but because saturated soil pushes with far more force than dry soil and dry-stack construction has no tensile strength to resist it. Build two 3-ft terraces separated by a wide bench instead of one 6-ft wall wherever the site allows.
Sizing the Base and the Batter
Two numbers govern whether the wall stands. The base thickness must be at least half the wall height, with a 12 in minimum — that mass is what stops the wall from rotating forward. The batter (backward lean) must be 1 in per 12 in of height, so each course sets back about an inch from the one below. That lean puts the wall’s center of gravity into the hill rather than out over open air.
| Wall height | Min. base thickness | Trench width | Total setback (batter) |
|---|---|---|---|
| 18 in | 12 in | ~24 in | 1.5 in |
| 24 in | 12 in | ~28 in | 2 in |
| 36 in | 18 in | ~34 in | 3 in |
| 48 in | 24 in | ~44 in | 4 in |
Trench width is the base stone width plus 12 in of room behind it for drainage stone. Wider and deeper is never wrong; thin and narrow is the most common cause of failure.
Step-by-Step Build
- Stake the line and call for utility locates. Run mason’s string along the wall face at finished height so you can see the line from the house and the yard before you dig. Dial 811 (or your local locate service) at least 48 hours ahead — retaining wall trenches are exactly the depth that finds buried gas and irrigation lines.
- Excavate the trench below the topsoil into firm subsoil. Dig out all sod, roots, and organic soil, then keep going until you hit undisturbed subsoil that does not deform under boot pressure. Your trench floor must be firm enough that the base cannot punch into it; if you find soft pockets, dig them out and backfill with compacted crusher run.
- Place and compact 6 in of crusher run in the trench floor. Spread it, water it lightly, and run the plate compactor until the surface rings hard and stops rutting. On walls over 3 ft, build the base to the thickness in the table above and compact it in 2-inch lifts — never dump the full depth and compact once, because the bottom half stays loose and the whole wall settles into it.
- Bury the first course. The bottom course should sit fully below finished grade — a minimum of one stone height, roughly 4–6 in for typical wallstone. A buried first course is what keeps the wall from kicking out at the toe, and it costs you nothing but a slightly deeper trench.
- Set the base course dead level, stone by stone. This is the slowest step and the one that pays. Set each stone with its flattest face down and largest face out, then check it front-to-back and side-to-side with a torpedo level. Shim low spots with crusher run underneath, never with a chip wedged under the front edge. Every course above inherits whatever error you accept here.
- Stack the wall with staggered joints and the required batter. Work one over two, two over one — each stone should bridge the joint below it. Set each course back 1 in per 12 in of wall height so the face leans into the hill. Check the batter with a level held plumb against the face and a spacer block, not by eye; walls drift vertical without you noticing.
- Fill the wall’s interior voids with hearting as you go. Hearting is the small angular chips and spalls packed tightly into the gaps between the big face stones. Do this course by course, not at the end — unhearted voids let stones rock, and a rocking stone eventually walks out of the wall. Pack it tight enough that nothing shifts when you push on the face.
- Build the #57 drainage chimney behind the wall as each course goes up. Line the back of the excavation with non-woven filter fabric, then place a minimum 12 in wide column of washed #57 stone directly behind the wall face, rising with every course. This is the component people leave out to save $200, and it is the reason their wall fails. Water that reaches the wall must be able to fall straight through it and out the toe.
- Wrap the fabric over the top of the drainage stone and backfill in lifts. Fold the filter fabric over the top of the #57 column to close the burrito so soil cannot migrate down into the voids and clog it. Backfill the remaining trench with native soil in 6–8 in lifts, tamping each one by hand near the wall — do not run a plate compactor directly against the back of a dry-stack wall.
- Set the capstones and grade the top. Choose the widest, flattest stones for the cap and set them slightly forward so they overhang the face by about an inch, throwing drip water clear. Cap stones are the ones that get sat on, walked on, and knocked; on any wall people will use, bed the caps in construction adhesive even though the rest of the wall is dry-laid. Finally, grade the soil above the wall to run water away from the top, not toward it.
When to Add Perforated Pipe
For a short wall on well-drained ground, the #57 chimney alone is enough. Add a 4 in perforated pipe at the base of the drainage stone — holes pointing down, sloped at least 1% (1 in per 8 ft) toward a daylighted outlet — whenever the wall is over 3 ft tall, longer than about 25 ft, cut into a slope that sheds water toward it, or built in heavy clay. Size the stone with the drainage gravel calculator; the detailing is identical to a standard French drain installation.
Pro tip: Sort your stone into three piles before you lay a single course — big flat base stones, general course stones, and wide flat capstones. Digging through one undifferentiated heap for the right stone is what turns a two-day wall into a five-day wall.
Troubleshooting Common Failures
The Wall Is Bulging Outward in the Middle
A belly in the middle third of the wall is hydrostatic pressure, almost without exception. Water is collecting behind the wall and pushing. The trigger is usually a missing or clogged drainage layer — either no #57 stone was installed, or it was installed without filter fabric and has since silted up with clay. Probe behind the wall with a length of rebar: if it drives easily through loose stone you still have a working chimney; if it stops in dense wet soil, the drainage is gone. There is no surface fix. Dismantle the bulged section back to sound courses, install fabric and #57 properly, and rebuild. While the wall is open, check whether a downspout or a swale is discharging into the backfill.
Courses Have Heaved and Gone Out of Level Over Winter
Frost heave lifts stone when water trapped in the base freezes and expands. It shows up as a section of wall standing higher than its neighbors in spring and only partly settling back. The cause is water held in the base — either the trench was cut into clay with no crusher run beneath, or the base was fine-graded material that holds moisture. Dry-stack walls tolerate small seasonal movement, so a half inch that recovers is not a defect. Cumulative annual heave is. Rebuild the affected run over a properly compacted crusher run base, and make sure the drainage chimney reaches all the way down to the base course rather than stopping partway.
The Whole Wall Has Settled or Tipped Forward
Uniform settlement means the base failed under load: too thin for the wall height, placed on topsoil or fill rather than firm subsoil, or never properly compacted. Tipping forward — the top leaning out past the toe — means insufficient batter, too narrow a base, or both. Neither is repairable from the outside. Measure the existing batter so you know what went wrong, then take the wall down, re-excavate to firm subsoil, rebuild the base to at least half the wall height, and re-lay at a true 1-in-12 batter.
Individual Stones Rock or Have Fallen Out
This is a hearting problem, and it is the easy one. Loose stones mean voids behind the face were never packed. Pull the offending stone, pack the cavity solidly with angular chips until nothing moves, and reset it with its flattest face bearing. If it happens wall-wide, the stone selection is wrong — rounded river rock cannot interlock and belongs on a decorative veneer, not a structural dry-stack face.
Mistakes That Cost the Most
- Skipping the drainage stone. The most expensive $200 anyone ever saves.
- Starting the wall on grade instead of below it. The first course must be buried or the toe kicks out.
- Building plumb because it looks neater. A vertical dry-stack wall is a wall that is already falling; you just cannot see it yet.
- Compacting the full base depth in one pass. Two-inch lifts, every time.
- Using rounded stone. Angular, flat-bedded stone interlocks; river rock rolls.
- Plate-compacting tight against the back of the wall. It shoves the face out.
Bottom Line
A dry-stack retaining wall is 70% preparation and 30% stacking. Cut the trench below the topsoil into firm subsoil, build a compacted crusher run base at least half the wall height and never under 12 in, bury the first course, lean the face back 1 in per 12 in of height, run a fabric-wrapped column of #57 stone behind the full height of the wall, and pack the hearting tight as you go. Keep the finished wall under 4 ft, or bring in an engineer. Do that and the wall will still be standing straight long after the mortared walls on the street have cracked. Size stone, base, and drainage aggregate with the retaining wall calculator and the crushed stone calculator before you order.