CMU & Block Retaining Walls in Utah County
A CMU retaining wall is concrete masonry block laid in mortar on a poured footing, with rebar and grout filling the cores so the wall works as one reinforced unit. It’s the right wall for a rigid, finishable face on a tight site, and Grandview builds them across Utah County and Salt Lake County under a B100 general contractor license.
When a cinder block retaining wall is the right choice
Most people asking about a “cinder block” wall mean CMU — the hollow gray 8x8x16 concrete masonry unit. Reinforced and grouted, it behaves much like a poured concrete wall, but goes up one course at a time with no formwork and no pump truck.
Block is the better call when access is tight — a side yard or a wall between two houses on a Provo or Sugar House lot a concrete truck can’t reach — and when the wall has a second job: a planter, a seat wall, a base for fence pilasters, or a face that will take stucco, brick, or stone veneer. Dry-stacked block can’t do any of that.
Where it loses to segmental block: on long terraces with machine access, a geogrid SRW is faster, cheaper per foot, and flexes instead of cracking. Above roughly six feet, poured concrete, a fully engineered wall with designed drainage, or a tiered wall with a terrace between usually beats 12-inch block with heavy steel. Every system we build is compared on our retaining wall page.
What goes into a block wall that stays plumb
Unreinforced block on a shallow footing is a garden wall, however many courses tall. A block retaining wall needs all of this:
- A reinforced poured footing. Wider than the wall, below frost depth, on compacted bearing soil. On the expansive clay the Utah Geological Survey maps across the Wasatch Front, we over-excavate and replace the bearing zone so the footing doesn’t ride the seasonal swell.
- Vertical dowels and bars. Rebar cast into the footing, lapped with bars running up the grouted cores at the engineer’s spacing — what makes the wall a cantilever instead of a stack.
- Bond beams. Horizontal courses of channel block carrying continuous bars, tying the vertical steel together.
- Grouted cores. Fine grout placed in lifts and consolidated around the steel. Over about five feet we leave cleanouts at the base so the inspector can confirm the cores are clear before grouting.
- Dampproofing on the soil side. Block and mortar are porous. Without a coating on the back, water migrates through and shows up as efflorescence and frost spalling on the face.
- Drainage and a cap. Drain rock, filter fabric, and perforated pipe at the footing, weep holes where detailed, and solid coping on top. With 100-plus freeze–thaw days a year here, an uncapped block wall is on a schedule.
Eight-inch block handles most residential walls to about four feet; taller walls or a driveway surcharge move to 12-inch block and closer bar spacing. Because much of Utah County and Salt Lake County sits in a high seismic design category along the Wasatch fault zone, expect the engineer’s detail to call for fully grouted, closely reinforced masonry under current Utah-adopted code, not the partially grouted walls common elsewhere.
How we build a CMU retaining wall
- Walk the site. Height, surcharge, access, soil, and where water goes now. If block is the right system you get a ballpark range; if not, you hear that.
- Engineer and permit. Most cities require a stamped design around four feet of retained height, lower with surcharge; verify thresholds with your city. We coordinate the design and run the permit.
- Pour the footing. Cut to design line, prepare the bearing soil, set dowels to the block module so every bar lands in a core, and pour an air-entrained mix.
- Lay, inspect, grout. Running bond, full mortar bedding, bond-beam courses where detailed. Reinforcing inspection if required, then grout in lifts and cap.
- Dampproof, drain, backfill. Soil-side coating, pipe and rock, fabric, then backfill compacted in thin lifts — never native clay against the block.
- Finish. Paint, stucco, or veneer when the design calls for it — stone and brick faces run through our masonry work.
What does a cinder block retaining wall cost in Utah?
As ballpark planning numbers, not quotes: a reinforced, grouted CMU retaining wall along the Wasatch Front typically lands between $35 and $65 per square foot of wall face installed, footing, drainage, and backfill included. Veneer, stucco, or a decorative cap adds to that; walls over six feet or under a driveway run higher once 12-inch block and heavier engineering come in. A site walk gets a budget range; a defined scope gets a firm estimate.
What moves the number on a block wall specifically: footing depth and whether clay must be replaced, the grout and steel schedule, whether material is staged by machine or carried in by hand, and the finish. Removing a failed wall first is its own line, priced up front as concrete demolition.
Questions we actually get
Can you build a retaining wall out of cinder block without grout and rebar?
Not one that retains anything you care about. Hollow, unreinforced block has little resistance to soil pushing on it and fails by tipping or shearing at a mortar joint. Every CMU retaining wall we build is reinforced and grouted to an engineer’s detail. If the budget only covers a plain stack, a short segmental wall is the safer spend.
Why is my existing block wall white and flaking on the face?
That’s efflorescence and freeze–thaw spalling: water is moving through the wall from the soil side. Usually the back was never dampproofed, the cores aren’t capped, or the drain is clogged with fines. Cleaning the face treats the symptom; the fix is at the drainage and the back of the wall, which sometimes means rebuilding.
Can a CMU retaining wall also hold a fence or a veneer?
Yes, and that’s one of its main advantages. Fence posts set into grouted cores or pilasters built into the wall, and the face takes stucco, paint, brick, or stone veneer. Say so at the design stage: a fence adds wind load, a veneer adds weight, and both change the footing and reinforcing the engineer specifies.
Tell us what your slope is doing
Send a few photos and rough dimensions, or ask us to walk the site. You’ll get a straight read on whether block is the right wall and a realistic budget range before anyone commits to anything. Our license is verifiable at dopl.utah.gov; this is one piece of our site, structure and envelope work. We reply within a couple of hours during business hours, a day at most.