HARDSCAPING • BISMARCK, ND
Retaining Walls in Bismarck, ND
Bismarck Landscape builds segmental block retaining walls for homes in Bismarck, Mandan and Lincoln: walls that hold back a slope, level out a yard, raise a planting bed or frame a patio.
In Bismarck, the block is the easy part. What keeps a wall straight through clay soil, spring melt and a hard freeze is what you never see: a packed gravel base, clean drainage stone behind the block, a drain pipe that actually goes somewhere and, on taller walls, reinforcement grid tied into the hill.
SITE CHECK • DRAINAGE • STRONG BASE
What Our Retaining Wall Work Includes
- A site visit to look at the slope, the soil, where water runs and what sits above the wall
- A call to 811 before any digging
- A layout for height, length, curves, steps and any tiers
- Excavation and a compacted gravel leveling pad
- A buried first course, so the wall isn’t sitting on top of the ground
- Clean drainage stone behind the block and a drain pipe with a real outlet
- Geogrid reinforcement where the wall height and the load above call for it
- Cap units glued down, and soil graded so runoff goes around the wall, not over it
- Coordination with an engineer when a wall is tall enough or loaded enough to need one
LOCAL CAUSES • CLAY • FROST • RUNOFF
Why Retaining Walls Fail in Bismarck
Most leaning, bulging or cracked walls in town come back to the same few causes:
- Water trapped behind the wall. Clay drains slowly. When water builds up behind a wall, it pushes on it. The National Concrete Masonry Association (NCMA) says proper drainage “will reduce the loading on the wall.”
- Frost in wet soil. Water that freezes behind or under a wall expands. NCMA says that in freeze-thaw climates, “only soils with low to moderate frost heave potential should be utilized” behind the wall, and that a deeper gravel zone helps reduce frost heave.
- A base that’s too thin or never packed, so the wall settles unevenly.
- No buried course, so the bottom of the wall can kick out.
- Extra weight on top the wall wasn’t built for, like a driveway, a parked car, a shed or a big snow pile. NCMA notes that “heavy snowfall” can govern a wall’s design.
- Runoff pouring over the top, washing out soil and saturating the backfill.
INSTALLATION • BASE • DRAINAGE • REINFORCEMENT
How We Build a Block Retaining Wall
We follow NCMA’s segmental retaining wall installation guide and best practices guide, plus the block maker’s specs.
The Base
- Call 811. North Dakota law requires anyone digging, homeowners included, to call at least 48 hours ahead. Line marking costs you nothing.
- Dig the trench and pack the soil at the bottom.
- Build a leveling pad at least 6 inches thick of compacted gravel. NCMA says it should extend at least 6 inches in front of and behind the first row of block.
- Get it perfectly level. NCMA warns that if the pad isn’t level, “the resulting wall will not be level.”
- Bury the first course. NCMA sets a minimum embedment of 6 inches, and more for taller walls or walls with a slope below them.
The Drainage
- Fill behind the block with clean gravel, at least 12 inches deep measured from the back of the block, per NCMA. That gravel lets water drain down instead of pushing on the wall.
- Lay a drain pipe at the bottom behind the wall. NCMA calls for a main drain at least 3 inches across, with outlets every 20 to 50 feet so the water actually leaves.
- Cap the backfill with about 8 inches of low-permeability soil on top, so rain doesn’t pour straight into the drainage stone.
- Grade a swale above the wall where the yard slopes toward it. NCMA says a swale should collect runoff so it doesn’t flow over the face.
Reinforcement for Taller Walls
- Add geogrid when the wall’s height or the load above it calls for it. NCMA says that when a wall gets taller than a plain gravity wall can safely handle, it should be a soil-reinforced wall. The minimum geogrid length is “60% of the total wall height but never less than 4 ft.”
- Compact the backfill in 6 to 8 inch layers, using only hand-operated compactors within 3 feet of the back of the wall, as NCMA specifies.
- Glue down the caps with a manufacturer-recommended adhesive, so they don’t shift or get knocked off.
MATERIALS • COMPARE FINISHES AND STRENGTH
Which Wall Material Is Right for You?
| Material | Good for | Things to know |
|---|---|---|
| Interlocking concrete block | Most home walls, curves, steps, raised beds | The most common choice. Flexible to work with and easy to match. |
| Natural stone | A rugged, natural look | Costs more per square foot |
| Wood timbers | Short, simple walls on a budget | Wood breaks down over time, unlike block or stone |
| Poured concrete | Walls tied into structures | Needs forms and footings, and costs more |
For most Bismarck yards, interlocking block is the best fit, and it pairs well with a patio. See paver patios in Bismarck.
PERMITS • HEIGHT • ENGINEERING
Do You Need a Permit for a Retaining Wall in Bismarck?
North Dakota’s state building code, which cities that enforce a building code must use, adopts the 2021 International Residential Code. That code exempts from permits retaining walls “that are not over 4 feet in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge.”
In plain terms:
- Under 4 feet, counting from the bottom of the base up, with nothing heavy on top: usually no permit under the model code.
- Over 4 feet, or holding up a surcharge like a driveway, a building or a steep slope: plan on a permit and an engineered design.
Cities can amend the code, so check before you build. The City of Bismarck’s Building Inspection Division takes questions. If you’re in Mandan or Lincoln, check with that city.
COST PLANNING • PRICES ARE ESTIMATES
How Much Does a Retaining Wall Cost in Bismarck?
Retaining walls are priced by the square foot of wall face, which is height times length. Homeyou’s Bismarck cost data, updated August 2026, lists:
| Wall type | Price per square foot of wall face |
|---|---|
| Interlocking concrete block | About $15 to $30 |
| Wood | About $20 to $25 |
| Natural stone | About $25 to $40 |
| Poured concrete | About $30 to $40 |
Some block wall examples at $15 to $30 per square foot:
| Wall size | Wall face | Estimated cost |
|---|---|---|
| 2 ft high × 20 ft long | 40 sq ft | About $600 to $1,200 |
| 30 in high × 20 ft long | 50 sq ft | About $750 to $1,500 |
| 3 ft high × 30 ft long | 90 sq ft | About $1,350 to $2,700 |
| 4 ft high × 40 ft long | 160 sq ft | About $2,400 to $4,800 |
That’s our math from Homeyou’s range. Homeyou also notes walls 3 feet or taller often need an engineer’s input, at about $200 to $500 or more. LawnStarter’s September 2026 Bismarck data puts the average hardscaping job, which includes patios, walls and walkways, at about $18,000. These are market estimates, not quotes. You get a written price after we see the site.
What Changes the Price?
- Height, since taller walls need more base, more drainage stone and often geogrid
- Length and curves
- Block style, from basic gray block to natural stone looks
- Soil and water, especially wet clay that needs more digging and gravel
- Access for equipment, block pallets and gravel
- Steps, corners, tiers and lighting
- Removing an old wall of failing timbers or block
- Engineering and permits for taller or loaded walls
For more local prices, see how much landscaping costs in Bismarck.
WALL REPAIR • EARLY WARNING SIGNS
Warning Signs Your Wall Needs Help
- Leaning forward or bulging in the middle
- Cracks or gaps between blocks that keep growing
- Wet soil, staining or water seeping out of the face after rain or snowmelt
- Soil washing out under the bottom course or over the top
- Caps that are loose or have fallen off
- Rotting, soft or bowed timbers in an old wood wall
A wall that’s starting to move rarely fixes itself. Often, the fix means taking the bad section down and rebuilding it with a proper base and drainage, often reusing the same block.
SERVICE AREAS • LOCAL SLOPES AND CLAY
Retaining Walls Across Bismarck, Mandan and Lincoln
- North Bismarck and Lincoln new builds: walk-out lots and graded slopes can need a wall to make the yard usable. Fill that was placed during construction needs to be packed properly before a wall goes on it.
- Northwest Bismarck: established yards where an aging timber wall or a sloped backyard is ready for an upgrade, often with a patio.
- South Bismarck near the Missouri River: lower ground where drainage deserves extra attention.
- Mandan: sloped lots where a wall can hold back the hill and create flat space.
A wall often works best as part of a bigger plan with grading, drainage and planting. See landscape design in Bismarck.
Questions
Retaining Wall FAQ
Answers about block wall construction, gravel bases, drainage, local permits, reinforcement and wall costs.
Need help comparing outdoor projects?
Browse typical projects and related services.
How much does a retaining wall cost in Bismarck?
About $15 to $30 per square foot of wall face for interlocking concrete block, based on Homeyou’s August 2026 Bismarck data. A block wall 30 inches high and 20 feet long runs about $750 to $1,500. Stone and poured concrete cost more. These are estimates, not quotes.
Do I need a permit for a retaining wall in Bismarck?
The 2021 International Residential Code, adopted through North Dakota’s state building code, exempts retaining walls up to 4 feet tall, measured from the bottom of the footing, unless they support a surcharge like a driveway or slope. Cities can amend it, so call Bismarck’s Building Inspection Division.
How deep should a retaining wall base be?
NCMA calls for a compacted gravel leveling pad at least 6 inches thick, extending at least 6 inches in front of and behind the bottom block. The first course should be buried at least 6 inches, and deeper for taller walls or walls with a slope below them.
Why is my retaining wall leaning?
Usually because water is trapped behind it, the base was too thin, or something heavy sits above it. Clay soil drains slowly, and frozen, wet soil pushes harder. The fix usually means rebuilding the bad section with a proper base, drainage stone and a drain pipe.
When does a retaining wall need geogrid?
When the wall gets taller than a plain gravity wall can safely hold, or when there’s a load above it like a driveway or slope. NCMA says the minimum geogrid length is 60% of the wall height but never less than 4 feet. Taller and loaded walls should be designed by an engineer.
Can I build a retaining wall on clay soil?
Yes, with the right base and drainage. Use a compacted gravel leveling pad, at least 12 inches of clean gravel behind the block, and a drain pipe with an outlet. NCMA says that in freeze-thaw climates, only soils with low to moderate frost heave potential should be used behind the wall.
Bismarck Landscape
Get a Retaining Wall Estimate in Bismarck
Got a slope that’s eating your yard, or an old wall that’s starting to lean? We’ll look at the site, tell you what the wall needs and give you a written estimate.
You can also see examples of typical projects, our other contact options or our FAQ.