Meridian Retaining Walls works with property owners on retaining walls in eight Treasure Valley cities: Meridian, Eagle, Star, Kuna, Garden City, Middleton, Caldwell and Nampa. Wall rules change at the city limit. Garden City, for one, caps retaining walls at 3.5 feet from the lowest adjacent grade, apart from its Boise Bench exception. In Meridian, a permit doesn’t come into play until a wall is over 4 feet from the bottom of the footing, unless it supports a surcharge.
Wherever you are in those eight cities, the services are the same: retaining wall installation for a new wall, and retaining wall repair for a replacement or a failing one, at a home or a commercial site.
- Statewide permit line
- Over 4 ft from the bottom of the footing
- Frost depth
- 24 in in Meridian, Eagle, Star, Caldwell and Nampa
- Dig notice
- 2 to 10 business days ahead
- Outside city limits, Canyon County
- Engineering for walls taller than 4 ft from the bottom of the footing
Retaining wall services across the Treasure Valley
Where your lot sits changes the job. Here’s how that plays out.
Sloped-lot and hillside retaining walls
For foothill lots and new subdivisions where the yard falls away, as one wall or as tiered retaining walls. On Eagle hillside lots, walls less than 10 feet apart whose combined height exceeds 4 feet must be engineered, under the city’s hillside checklist (updated March 2024).
Canal-side and ditch-bank retaining walls
For lots that back onto an irrigation easement. Tell us which district when you call, and see retaining walls near canals. The Nampa & Meridian Irrigation District allows work that affects water flow only from October 15 to March 15, unless its water superintendent sets different dates.
Retaining walls and drainage on wet ground
For river-bottom lots and high groundwater, where the wall and its retaining wall drainage are planned together. Middleton’s residential permit application asks whether the lot is in a floodplain.
Which city is your wall in?
Tell us the length, the height and what the wall holds back.
Retaining walls by city: permit office, review time and local rule
Names and addresses are the way each city lists them. Where a cell says to confirm, call that office before you plan around it.
| City | Permit office | Permit height | Review time | Local rule |
|---|---|---|---|---|
| Meridian | Building Services, 33 E. Broadway Avenue | Over 4 feet from the bottom of the footing to the top of the wall. A wall supporting a surcharge loses the exemption. | 7 to 10 business days for a residential permit, as last published by the city in 2021. | Inside the clear vision triangle, 40 feet along each road at an intersection, fences stop at 3 feet above the lowest adjacent street grade; the text names fences, not retaining walls. |
| Eagle | Building Department for a wall over 4 feet, Planning and Zoning for the fence permit; the city’s address is 660 E Civic Lane | Over 4 feet for the building permit. | Confirm with the Building Department. | A residential wall in a front yard or along any street needs a fence permit at any height. |
| Star | Building Department, 10769 W. State St. | Over 4 feet from the bottom of the footing. | 2 to 4 weeks for small residential review. Each correction adds 3 to 4 more, so one round makes 5 to 8 weeks. No paid expediting. | Finish grade within 3 feet of a lot line must match the neighbor’s grade and be no steeper than 2 to 1, or a permanent retaining wall must be built. |
| Kuna | Building Department, City Hall, 751 W. 4th Street | Over 4 feet high, measured from the bottom of the footing. | Applications are processed in the order received. Ask the Building Department for current timing. | Any lot with a slope exceeding 6 feet in height “shall include a retaining wall with drainage designed by an Idaho registered Professional Engineer”. Ask the city whether that covers the wall itself or only its drainage. |
| Garden City | Building Division, 6015 N Glenwood St | Stamped Idaho-engineer calculations for walls more than 4 feet from the bottom of the footing. Zoning caps height first. | Confirm building review with the Building Division. A floodplain permit for re-grading or filling runs up to 15 working days per review cycle. | Retaining walls are capped at 3.5 feet from the lowest adjacent grade, except next to the Boise Bench along the southern city limits, and barred within 5 feet of the Greenbelt or Nature Path. |
| Middleton | Building Department, 1103 West Main Street | Confirm the city’s retaining wall rule with the Building Department. | Confirm with the Building Department. | The comprehensive plan reports domestic wells from about 28 feet deep, many artesian wells and more than 137 miles of open-ditch waterways in the area. |
| Caldwell | Building Safety Division, 205 South 6th Ave. | Confirm with the Building Safety Division. | Not more than 5 to 7 working days for residential plan review, with a complete submittal. | A footing at the city’s 24 inch frost depth lands inside the 20 to 40 inch band where the Purdam soil, described near Caldwell, has a cemented hardpan. |
| Nampa | The city’s building office. Confirm the address with the city. | The building code exempts walls not over 4 feet in height unless supporting a surcharge. | Confirm with the city. | The fence and wall section measures height at grade, within 6 inches of the bottom. |
Found your city? Call us, tell us which one your lot is in, and have the wall’s length and height handy.
City or county: which office handles a retaining wall on my lot?
If your lot is inside city limits, it’s the city office in the table above. Outside city limits, it’s the county.
In Canyon County that’s the Building Department, part of Development Services, in Room 310 at 111 N. 11th Ave in Caldwell. Its building permit checklist, revised January 12, 2026, requires engineering for a retaining wall taller than 4 feet as measured from the bottom of the footing. The county may also want written confirmation from the irrigation district.
Canyon County’s fee table, adopted March 20, 2025, charges $30 on the first $1,000 of value and $30 per additional $1,000 up to $5,000. So a $5,000 wall comes to $30 + 4 x $30 = $150, plus plan review at 16 percent of that, $24. That’s $174 in all. Start work before the permit and the fees double.
Don’t carry the Canyon County figures over to Ada County. If your lot is in unincorporated Ada County, confirm the wall rule and the permit fee with that county’s building office before you budget.
Not sure which side of the city line your lot is on? Give us the street address when you call.
What stays the same for a retaining wall in every city
- The state code’s 4 foot line Under Idaho’s adopted residential code, a wall of 4 feet or less from the bottom of the footing to the top needs no building permit unless it supports a surcharge. It needs an engineered design once it retains more than 48 inches of unbalanced fill, or stands more than 24 inches tall and carries a load besides soil. See retaining wall permits for how the 4 feet is counted.
- A 24 inch frost depth, where one is published Meridian, Eagle, Star, Caldwell and Nampa each publish 24 inches, with a 20 psf ground snow load.
- Irrigation districts and the October 15 to March 15 window The Nampa & Meridian district charges a $1,200 application fee and allows work that affects water flow only between those dates unless the water superintendent says otherwise, with plans due by January 15. Application fees elsewhere run from $750 at Settlers to $4,250 at Pioneer.
Two state rules hold in all eight. Idaho’s dig law says the locating service has to be notified 2 to 10 business days before digging, and Dig Line’s locates at 811 are free. A contractor must be registered with the state for any job over $2,000 in labor and materials. Without that registration, the state says, a contractor cannot obtain a building permit.
Retaining wall service area questions
Who builds retaining walls in my area?
An independent local retaining wall contractor who works in your city, and we’ll help you find one. That goes for lots in Meridian, Eagle, Star, Kuna, Garden City, Middleton, Caldwell and Nampa. Tell us which city yours is in when you call or fill in the form.
What size retaining wall needs a permit?
Under the state code, any wall over 4 feet from the bottom of the footing to the top, or one that supports a surcharge. Meridian, Star and Kuna measure it the same way. Some cities add their own rules on top: Garden City’s 3.5 foot cap and Eagle’s fence permit are in the table above. Star requires the wall permit for walls four feet and greater before it issues a grading permit.
How much is a retaining wall permit?
It depends on the office. Meridian’s residential worksheet dated June 1, 2026 builds the fee from a $50.00 base plus an amount based on the work. Kuna’s small-structure table starts at $65 for work valued up to $2,000 and adds $11.35 per additional $1,000 up to $25,000. The retaining wall cost page sets permit fees beside the price of the wall itself.
What if I’m outside city limits?
Then your permit goes through the county. Canyon County says its building permit fees average 2% of total market value, and an inspection called in is scheduled for the following business day. In Ada County, call the county’s building office first to confirm its rule and fees.
Don't see your question? Call (208) 445-1999.
Sources and review date
Reviewed October 2026. Sources: building codes, permit handouts and fee schedules of Meridian, Eagle, Star, Kuna, Garden City, Middleton, Caldwell and Nampa; Canyon County Building Department; Idaho residential code, dig law and Contractors Board; Dig Line; Nampa & Meridian, Settlers and Pioneer irrigation districts; USDA soil survey.