Meridian Retaining Walls helps Garden City, Idaho homeowners with low retaining walls on river, floodplain and infill lots. Start with two city facts. The city estimates that 74 percent of its properties are in the 100-year floodplain, and its zoning puts a cap on how tall a retaining wall can be. Both are covered below.
On floodplain ground, the soil that goes behind the wall is part of the job too. Before you call, jot down the wall’s length, its height on the low side and whether fill goes behind it. A few photos help.
- Zoning height cap
- 3.5 feet from the lowest adjacent grade, except next to the Boise Bench
- Properties in the 100-year floodplain
- 74 percent, by the city's estimate
- Greenbelt and Nature Path setback
- 5 feet
- Floodplain review
- Up to 15 working days per cycle
Retaining walls on Garden City lots: garden, riverside and floodplain walls
It’s a small city: 12,654 residents and a homeownership rate of 63.1 percent in the 2024 American Community Survey.
Low garden and lot-edge retaining walls
You’d use one on an infill lot with a bed to hold or a grade change at the boundary. A small garden retaining wall has a ceiling here: zoning caps wall height at 3.5 feet from the lowest adjacent grade, except next to the Boise Bench.
Retaining walls near the Greenbelt or the river
On a riverside lot, measure the setbacks first. The city’s floodplain application asks for a bank-stability narrative, a written account of how the bank stays put, for work within 25 feet of the river’s ordinary high water mark. The building permit side is on the retaining wall permits page.
Walls with fill or re-grading on floodplain ground
If you’re raising or leveling the yard, plan on the floodplain permit. Each review cycle runs up to 15 working days, and every resubmittal starts a new one. Water behind the wall is covered on the retaining wall drainage page.
Thinking about a wall in Garden City?
Have the measurements handy and give us a call.
How tall can a retaining wall be in Garden City?
Three and a half feet. That’s the zoning cap, and it’s measured from the lowest adjacent grade. The one exception is ground next to the Boise Bench along the southern city limits.
There’s a second number to know. The city’s residential application requires stamped Idaho-engineer calculations for walls more than 4 feet from the bottom of the footing, and that measurement starts underground, as the drawing shows. Idaho’s adopted residential code starts its permit line in the same place: a wall not over 4 feet from the bottom of the footing needs no building permit unless it supports a surcharge.
Good to know The two numbers start in different places, the cap at the lowest adjacent grade and the 4 feet at the bottom of the footing. A wall under the cap can still sit close to the engineering line. Ask the Building Division how it measures before you settle on a design.
The zoning cap and the footing measurement come from different city documents, so ask the Building Division how they work together before anyone draws a taller wall.
Check your wall against the permit ruleor send us the details
What do Garden City permit fees add to retaining wall cost?
These come from the city’s 2026 fee schedule. They’re the lines a wall could run into.
| Fee | Amount |
|---|---|
| Initial set-up fee | $80. |
| Building permit, work valued up to $2,000 | $150. |
| Each additional $1,000 of value, up to $25,000 | $17.08. |
| Structural plan review, projects under $20,000 | $155 per hour. |
| Work in the riparian zone | $320. |
| Non-structural floodplain development | $240. |
| Development in the floodway | $1,200. |
Source: City of Garden City fee schedule, 2026.
Which lines hit your wall is up to the city, so check with the Building Division before you budget. And remember these fees come on top of the wall itself. Typical price ranges by wall type are on the retaining wall cost page.
Lot near the river? Tell us the distance to the water when you call.
Call (208) 445-1999 to talk it throughor request a quote online
Floodplain ground under a Garden City retaining wall: permits, and how long review takes
Re-grading or filling a property takes a floodplain permit here. The city allows up to 15 working days per review cycle, and a resubmittal starts a new cycle. Before you order material, ask the city whether the gravel and soil behind a short garden wall count as fill.
Closer to the water, the application asks for more. Work within 25 feet of the river’s ordinary high water mark needs a bank-stability narrative. Floodway work needs an engineer’s no-rise documentation.
The residential permit application shows example design criteria of a 24 inch frost depth and 1,500 psf soil bearing (psf is pounds per square foot). Those are examples printed on a form, not tested numbers for your lot.
Who reviews the plans, and where to apply
The city contracts out plan review and inspection, to SAFEbuilt and the state licensing division. You still submit the permit through Garden City, and the city routes it from there.
Ask the Building Division how it wants your application sent: 6015 N Glenwood St, phone (208) 472-2921. The areas page sets these rules in their Treasure Valley context.
Checking your wall against the height cap?
Tell us what you are weighing and we will talk it through.
What to look for in a retaining wall quote on a floodplain lot
- Height from the lowest adjacent grade In feet, checked against the zoning cap. Ask for a second height from the bottom of the footing too.
- A site plan with what the application asks for Floodway, floodplain and easements should all be on it.
- The floodplain permit for any fill Is it in the price, who files it, and are its review cycles in the schedule?
- Distance to the Greenbelt or Nature Path Measured in feet, against the city’s setback.
Garden City retaining wall questions
Can I build a retaining wall without a permit in Garden City?
Sometimes, as far as the building permit goes. Under the residential code as adopted in Idaho, a wall not over 4 feet from the bottom of the footing needs none unless it supports a surcharge, meaning added weight above the wall. The zoning height cap is a separate rule, and re-grading or filling a property needs a floodplain permit of its own.
Can I build a 4 foot retaining wall in Garden City?
Not under the zoning cap set out above, unless your lot is next to the Boise Bench. Ask the Building Division whether any other route to a taller wall applies to your lot.
Does filling behind a retaining wall need a permit?
It can. The city requires a floodplain permit for re-grading or filling a property, and its fee for non-structural floodplain development is $240. Ask the Building Division whether your wall’s backfill counts.
How close to the Greenbelt can a retaining wall go?
No closer than 5 feet. City zoning bars walls within that distance of the Greenbelt or the Nature Path.
Can a retaining wall be on the property line?
That’s a question for the Building Division, so ask what distance it wants from a lot line. The residential application asks for a site plan showing easements, and your wall gets drawn against them. Lot-line walls in general are covered on the retaining wall permits page.
Don't see your question? Call (208) 445-1999.
Sources and review date
Reviewed October 2026. Sources: City of Garden City fence, floodplain and building services pages, permit applications and 2026 fee schedule; Idaho residential code; 2024 American Community Survey via DataUSA; block industry guidelines.