Type the length, the exposed height and the installed rate from your bid. Drainage and geogrid get their own line, so you can see whether a bid priced them.
9 of 23code sources set a height other than 4 ftHyreYard read 23 model codes and state or city sources on September 5, 2026. 5 are stricter than the model, and 12 measure from a different point.
Retaining wall cost = face area (length × exposed height) × the installed rate on your bid, plus drainage and geogrid. A 40 ft wall with 3 ft of face at $45 per sq ft, plus $500 of drainage, is $5,900. Ask your building department where it measures permit height.
Work out your wall
Arithmetic on your figures. Nothing is stored or emailed.
40 ft long, 3 ft of face, $45 per sq ft of face from a bid, $500 on the drainage line. Face 120 sq ft, total $5,900. The $45 is an example rate; type the one on your proposal.
The same wall, taller
40 ft long, 4.5 ft of face, the same $45, $800 on the drainage line. Face 180 sq ft, total $8,900. The note now asks you to check permit and engineering with your building department before you order block.
The 3 ft 6 in wall that is over 4 ft
The model code measures from the bottom of the footing to the top of the wall. A 3 ft 6 in face on an 8 in buried footing is 4 ft 2 in by that measure. A parking pad above it is a surcharge, which removes the exemption at any height.
Face area × the rate on your bid, plus a drainage line you type. Leave the rate at 0 until you have a written bid.
The drainage behind a wall is part of the wall
Wet soil pushes harder than dry soil. The drainage detail lets water leave before it builds pressure behind the blocks.
What the drainage detail includes. Free-draining stone right behind the blocks, fabric that keeps soil out of the stone, a perforated pipe at the base, and an outlet lower down where the water is allowed to go.
All of it is buried. None of it shows once the wall is finished, so ask for each item in the quote in writing.
What sits above the wall counts. A driveway, a parked car, a shed or a slope rising behind the wall is a surcharge. It changes the design and, under the model code, the permit.
The “four foot rule” depends on where you live
We read 23 code and department sources on 5 September 2026: 4 model codes and 19 state or city sources. There is no national retaining-wall height law.
9 of 23 publish a permit height other than 4 ft, or none at all. 5 are stricter than the model code.
12 measure from a different point. The model code measures from the bottom of the footing. Others use the top of the footing, the grade at the face, or the unbalanced fill.
17 of the 23 depart from the model in some way: a different height, a different measuring point, an extra trigger, or no stated rule.
Permit height and where it is measured, in seven places
A sample from our research study, retrieved 5 September 2026. Each row is that jurisdiction’s own code or bulletin.
Jurisdiction
Permit height
Measured from
Menlo Park, CA
2 ft
Top of the footing to the top of the wall
Phoenix, AZ
3 ft
Top of footing to top of wall, not the IRC’s bottom of footing
San Diego, CA (city)
3 ft
Top of footing to the highest point on the wall (including caps). Zoning height is a different number: finished grade on the low side to the top.
New York City, NY
4 ft
Top of the footing to the top of the wall, not the IRC’s bottom of footing
San Antonio, TX
4 ft
Grade level at the front of the wall to the top of the wall (exposed height)
Seattle, WA
4 ft
Bottom of the footing (even if under grade) to the top of the wall
Cary, NC
5 ft
Wall height and unbalanced fill measured from grade at the face of the wall (Cary handout)
All 23 rows, with citations, are in the retaining wall permit threshold study. Rules change; confirm with your building department.
Four questions for your building department
What varies
What to ask
The permit height
“Above what height does a retaining wall need a permit here?”
The measuring point
“Measured from where: bottom of footing, top of footing, or grade at the face?”
The surcharge rule
“There is a driveway, slope or shed above it. Does that change the answer?”
The engineering trigger
“When do you require a stamped design?” IRC R404.4, where adopted, requires engineering above 48 in of unbalanced fill, or 24 in with extra lateral load.
Model-code text is a starting point. Adoption and amendments are local.
The soil behind the wall changes the design
The block is the part you choose. The soil it holds back decides how hard it has to work.
Look it up for free. USDA NRCS Web Soil Survey returns the mapped soil at your address, its drainage class and its shrink-swell potential, with no account.
Clay can shrink and swell. NRCS classes linear extensibility of ≥ 9.0 as “Very High”. Our soils study works that out to about 1.08 inches per foot or more of unconfined movement. Movement in the ground is smaller, because the soil is confined.
Backfill with stone, not the dug-out clay. Clay against the wall holds water and moves with the seasons. Ask for imported free-draining stone wrapped in fabric.
Geogrid is structure. On taller block walls, layers of grid run back into the soil and tie it to the wall. Where the design calls for it, leaving it out makes a weaker wall with the same face.
The order a wall goes in
1
Call 811 before you dig
The call is free, and utilities mark buried lines before a trench goes in.
2
Settle height, measuring point and surcharge
Take those three facts to your building department before anything else.
3
Look up the soil
Web Soil Survey gives drainage class and shrink-swell potential. Both change the design.
4
Agree the design, then the price
Engineer or not, geogrid or not, and the drainage detail. These set the price.
5
Dig and compact the base trench
The first course sits on compacted stone, buried below finished grade at the front.
6
Build and backfill together
Free-draining stone behind the blocks, fabric against the soil, and the pipe at the base falling to its outlet. Compact in layers as the courses rise.
7
Send surface water elsewhere
Cap the wall and grade the top so rain runs away from the backfill.
What a good retaining wall quote says
The drainage detail, including the outlet
Stone width, fabric, pipe, and where the pipe comes out. “It will drain away” is not a place.
Geogrid, if the design has it
Its layers, spacing and length back into the soil.
The base course
How deep the first course is buried and what it sits on.
Who handles the permit
Who finds out if one is needed, who applies and who pays. 5 places in our study are stricter than the model’s 4 ft.
Whether an engineered design is included
Near either IRC R404.4 trigger, agree who pays for the stamp before you sign.
A price per sq ft of face and nothing else
That prices what you see. Ask what drainage, geogrid and base are behind it.
Backfill with the dug-out soil
If the quote does not name imported free-draining stone, ask what goes behind the wall.
Reading a wall you already have
Leaning out at the top
The top is being pushed while the base holds. Hang a plumb line, photograph it with the date, and repeat after a wet season to see if it is still moving.
Bulging mid-run
One section is behaving differently from the rest: a blocked drain or missing grid are possible causes. That is a question for an engineer.
A wet or stained face after rain
Water is coming through the wall, not around it. The drainage behind it may be missing or clogged.
The drain outlet
Find where the pipe comes out and look at it in heavy rain. A drain that never runs may be blocked or connected to nothing.
Terms on a wall quote
Unbalanced fill
The difference in soil height between the two sides: what the wall actually holds back.
Surcharge
Any load on the soil above and behind the wall: a driveway, car, shed or rising slope.
Exposed face
The height you can see. Shorter than bottom-of-footing to top-of-wall.
Geogrid
Polymer grid laid in layers back into the soil to reinforce a block wall.
Free-draining backfill
Open-graded stone behind the wall that lets water reach the pipe.
Embedment
How deep the bottom course is buried below grade at the front.
Daylight
Where the drain pipe comes out at the surface.
What this calculator cannot see
Structure. It is face area times a rate. Where your jurisdiction requires an engineered design, this is not one.
Your permit rule and your soil. Both are local. Your building department and Web Soil Survey have them.
Drainage and geogrid prices. They are a separate line so you can see whether a bid includes them. HyreYard does not build walls. Figures checked 5 September 2026.
Questions this calculator answers
How much does a retaining wall cost?
Face area times the installed rate on your bid, plus drainage, geogrid, digging and haul-away. HyreYard publishes no national rate: a 3 ft garden wall and a 5 ft wall holding a driveway are different structures.
Do I need a permit for a retaining wall?
It depends on your jurisdiction. The model IRC R105.2 exempts walls up to 4 ft from the bottom of the footing that carry no surcharge, but cities adopt and amend it. Ask your building department with the height and what sits above.
Is 4 feet the legal limit everywhere?
No. There is no national retaining-wall law. Of 23 sources we read, 9 set a height other than 4 ft or none, and 5 are stricter.
What is a surcharge?
Extra load above and behind the wall: a driveway, a parked car, a shed or a rising slope. Under the model code, a wall with a surcharge is not exempt from a permit at any height.
Why is drainage a separate line?
So you can see whether a bid includes it. Water behind a wall adds pressure, and the stone, fabric, pipe and outlet are buried where you cannot check them later.
When does a retaining wall need an engineer?
IRC R404.4, where adopted, calls for an engineered design above 48 inches of unbalanced fill, or above 24 inches with extra lateral load. Your jurisdiction may set its own trigger.
Does this include the footing and haul-away?
Only if your rate includes them or you add them to the drainage line. Ask the bidder what the face rate covers.
Sources and methodology
Figures dated September 5, 2026. Last reviewed .
2024 IRC R105.2, work exempt from permit (International Code Council, retrieved August 26, 2026). Model code. The 4 ft figure is measured from the bottom of the footing and does not apply to a wall supporting a surcharge.
IRC R404.4, retaining walls (International Code Council, retrieved August 26, 2026). Engineering design above 48 in of unbalanced fill, or 24 in with additional lateral load, where adopted. Confirm your edition.
Guide to segmental retaining walls (Concrete Masonry & Hardscapes Association, retrieved August 26, 2026). Drainage fill behind the units and geogrid as designed parts of the wall.
Web Soil Survey (USDA Natural Resources Conservation Service, retrieved September 5, 2026). Drainage class and shrink-swell potential for your lot. A survey map, not a site test.