A retaining wall in Minnesota generally needs a building permit when it is more than 4 feet tall, measured from the bottom of the footing to the top of the wall, or when it holds back a surcharge such as a driveway, a slope or a building, at any height. That is the rule in the Minnesota State Building Code, which follows the model code. Many cities then add zoning rules of their own on setbacks, easements, drainage and shoreland, and some want a permit or a review for shorter walls too.
So the building code sets a floor, and your city decides the rest. Here is how the height is measured, what counts as a surcharge, when an engineer comes in, and what to ask before the first block goes down.
How the 4 feet is measured
From the bottom of the footing to the top of the wall. On a block wall the footing is the compacted base and the buried first course, so a wall that shows 3 1/2 feet above the lawn can be over 4 feet by the code's measure. Measure your plan from the bottom of the base trench, not the finished grade.
Cities also differ on how they treat a cap, a fence or a railing on top of a wall, and how they measure a wall that steps up along a slope. Ask when you call.
What is a surcharge?
A surcharge is extra load on the soil behind the wall beyond the soil itself. The code exemption does not cover a wall that supports a surcharge, so a wall under 4 feet can still need a permit. Common surcharges:
- A driveway, parking pad or road behind the wall, where vehicles load the soil.
- A slope rising above the top of the wall instead of flat ground.
- A house, garage, shed, deck footing or pool near the top of the wall.
- A second wall above it, when the upper wall is close enough to load the lower one.
When does a retaining wall need an engineer?
When a permit is required for height or surcharge, cities commonly ask for a design stamped by a Minnesota-licensed professional engineer. The engineer sets the base depth, the geogrid layers and how far back they run, and the drainage. Block makers publish design tables for their walls, and short walls with no surcharge are built from those. Tall or loaded walls get a design for the site.
City rules beyond the building code
Even a short wall can run into zoning. Things cities commonly regulate:
- Setbacks from property lines, and sometimes a maximum height near the line.
- Drainage and utility easements, where cities often do not allow walls or other structures.
- Drainage: a wall cannot send water onto a neighbor's lot or block a drainage swale.
- Shoreland, floodplain and wetland areas, which carry extra rules and sometimes watershed district review.
- Grading or land-disturbance permits when a project moves a lot of soil.
- Walls in the front yard or near the street, including sight-line rules at driveways and corners.
What to ask your city before you build
Call the building or planning department with a rough sketch and ask:
- 1Does a wall this tall, measured from the bottom of the footing, need a building permit here?
- 2Does anything behind the wall count as a surcharge for your review?
- 3Do you need an engineered design, and at what height?
- 4What setback applies from my property line, and is there an easement where the wall would go?
- 5Am I in a shoreland, floodplain or watershed district area?
- 6How do you measure terraced walls?
Why a permit is not the only reason to build it right
Most failed walls in the Twin Cities were short enough that nobody inspected them. They lean because water behind them froze, or the base was shallow and uncompacted. A wall under the permit threshold still needs a compacted base, drainage stone, a perforated pipe to daylight and fabric against the native soil. The permit threshold decides the paperwork; the frost decides whether the wall lasts.
What JMB Builders does
JMB Builders is a licensed Minnesota residential building contractor (BC809005) based in Zimmerman, working across the Twin Cities metro. Retaining walls are quoted after a site measure. We check your city's rules at the visit, and when a wall needs an engineered design and a permit, both are part of the job. Paid by check or direct deposit. Call 763-204-2099.
- Block retaining wall installation — jmbbuildersmn.com/services/hardscapes/block-retaining-wall
- Retaining wall drainage and frost — jmbbuildersmn.com/services/hardscapes/retaining-wall-drainage-and-frost
- Retaining wall replacement — jmbbuildersmn.com/services/hardscapes/retaining-wall-replacement
- Tiered retaining walls for a terraced yard — jmbbuildersmn.com/services/hardscapes/tiered-retaining-wall-terraced-yard
- Boulder retaining wall — jmbbuildersmn.com/services/hardscapes/boulder-retaining-wall
- Landscape timber wall replacement — jmbbuildersmn.com/services/hardscapes/landscape-timber-retaining-wall-replacement
Frequently asked questions
How tall can a retaining wall be without a permit in Minnesota?
The Minnesota State Building Code generally exempts retaining walls 4 feet or less, measured from the bottom of the footing to the top of the wall, unless the wall supports a surcharge. Cities can add zoning rules for setbacks, easements and drainage, and some review shorter walls. Call your city before you build.
Is the 4 feet measured from the ground?
No. It is measured from the bottom of the footing to the top of the wall, so the buried base course counts. A block wall that shows about 3 1/2 feet above the lawn can be over 4 feet by that measure. Ask your city how it treats caps and railings on top.
What does surcharge mean for a retaining wall?
It is extra load behind the wall beyond level soil: a driveway, a slope rising above the wall, a building or a second wall close above it. A wall that supports a surcharge is not covered by the code's short-wall exemption, so it can need a permit and an engineered design even under 4 feet.
Do I need an engineer for a retaining wall in Minnesota?
Short walls with no surcharge are usually built from the block maker's published tables. Walls over the permit height, or holding back a driveway, slope or building, are commonly designed by a Minnesota-licensed engineer, and cities often require the stamped design with the permit application. Your city can tell you its threshold.
Can I build a retaining wall on the property line?
Many cities require a setback from the property line, and walls are often not allowed in drainage and utility easements, which commonly run along lot lines. The wall also cannot send water onto the neighbor's lot. Check your city's zoning rules and your survey or plat before you dig.
Does replacing an old retaining wall need a permit?
Usually the same rules apply as for a new wall: height from the bottom of the footing, any surcharge, and your city's zoning. Replacing a tall wall or one holding back a driveway can need a permit and an engineered design even though a wall was there before. Ask your city with the height and what sits behind it.
