Poured Concrete Retaining Wall vs Block: Footings, Drainage, Cost and When Each Wins

In the poured concrete retaining wall vs block decision, block wins for most yard walls: a segmental block wall is dry-stacked on a gravel pad that, on firm soil, doesn’t have to go below the frost line, it can shift slightly without cracking, and it needs no forms or concrete trucks. A poured concrete wall is rigid and is normally built on a frost-protected footing, so it earns its place when you want a vertical face or an engineer is designing the wall as part of a driveway, garage or other structure.

Poured concrete vs block retaining wall at a glance

	Segmental block wall	Poured concrete wall
How it holds soil	Weight of dry-stacked units, plus geogrid layers when taller	Reinforced concrete stem tied to a footing
Behavior	Flexible; units can shift without visible distress	Rigid; can crack if the ground moves
Footing	Crushed stone or unreinforced concrete pad, 6 in minimum; frost depth not required on firm soil	Concrete footing, frost-protected (usually below the frost line)
Drainage	At least 12 in of gravel behind the units	Free-draining stone behind, with weep holes or a drain
Face	Steps back a little each course; curves are easy	Can be dead vertical
Build	No mortar or forms; most units can be set by one worker	Forms, steel, concrete delivery and cure time
Engineering	Over 48 in of retained soil, or 24 in with added load	Same rule

How each wall holds back soil

A segmental retaining wall is a gravity wall. CMHA’s guide to segmental retaining walls describes concrete units stacked without mortar that rely on interlock, friction between units and their own weight to keep from sliding or tipping. Each course sets back slightly, and that batter adds stability. Taller walls add layers of geogrid that run back into the compacted soil, so the block and the reinforced soil act as one big gravity mass. Our article on segmental retaining walls covers the systems in more depth.

A poured wall works differently. Typically it’s one rigid piece of reinforced concrete: a vertical stem tied with steel to a footing, so the footing and the steel resist the soil’s push instead of the weight of stacked units. That rigidity is its strength and its weakness. CMHA notes that rigid walls may crack when the ground moves, while segmental units can move and adjust relative to one another without visible signs of distress.

That difference shows up again at repair time. A block wall that bulges or leans can usually be taken down to the problem and relaid. A cracked or tipped poured wall usually needs structural repair or replacement.

If “block” means cinder block

Some people mean mortared concrete masonry units, the hollow gray block, when they say block wall. That’s a rigid wall too. It’s typically built on a poured footing with steel and grout in the cores, so in this comparison it behaves like the poured wall, not the stacked landscape block.

Footings and frost: the biggest difference

This is where the two walls really split.

Block walls sit on a gravel pad. CMHA’s guide calls for a leveling pad of crushed stone or unreinforced concrete at least 6 inches thick, extending about 6 inches past the front and back of the bottom course. Because segmental walls are flexible structures, it says the footing does not need to be placed below the frost line, provided the soil has enough bearing capacity. Our guide to retaining wall base depth covers the trench, the pad stone and how deep to bury the first course.

Poured walls are built for frost. A rigid wall that frost lifts unevenly can crack or tip, so its footing is normally protected from frost. The 2021 IRC’s frost protection section requires foundation walls, piers and other permanent supports of buildings and structures to be protected from frost, and the first method it lists is extending them below the frost line your jurisdiction enters in the code’s climate table (Table R301.2). How that applies to a freestanding retaining wall is your building department’s call, so ask what footing depth it wants; our guide to frost line depth by state explains where that number comes from.

In cold climates that means a deep trench and a lot of concrete below grade that nobody ever sees. In warm climates with shallow frost, the gap between the two walls narrows.

Drainage behind the wall

Trapped water adds pressure behind any retaining wall, so both types need a way to let it out.

For block, CMHA calls for free-draining gravel at least 12 inches behind the units, which removes incidental groundwater, keeps hydrostatic pressure from building and lets the backfill be compacted without big forces on the block.

For a poured wall, the drainage has to be built in, because a solid concrete face can’t let water through. Ohio DOT’s spec for drainage of structures shows the idea at highway scale: when the plans don’t say otherwise, it places porous backfill of No. 57-size stone or gravel at least 2 feet thick behind the full length of retaining walls, with 2 cubic feet of bagged No. 3 stone at each weep hole to hold the backfill in place, and drain pipe in the backfill where the plans call for it. A backyard wall is smaller, but the principle is the same. Our guide to retaining wall drainage covers stone, pipe and outlets for both.

Height limits and when you need an engineer

The height rule is the same for both. The 2021 IRC’s retaining wall section, R404.4, requires an engineered design for any wall not supported at the top that retains more than 48 inches of unbalanced fill, and for any wall over 24 inches tall that resists lateral loads in addition to soil, such as from a driveway above it. Those walls must be designed against overturning, sliding, excessive foundation pressure and water uplift, with a safety factor of 1.5 against sliding and overturning. The section doesn’t cover foundation walls that support a building.

Under those limits, block walls follow the manufacturer’s height charts. CMHA adds that segmental walls should be engineered when they carry surcharge or live loads, sit on poor foundation soil, or face unusual conditions. Your town may be stricter than the IRC; our retaining wall design guide walks through heights, geogrid and permits.

Cost and build time

CMHA calls segmental walls a cost-effective alternative to conventional cast-in-place concrete walls, and gives the reasons: on-site soil can usually be used as backfill, there’s no extensive formwork or heavy equipment, and most units can be set by one worker. Dry-stacking also goes up fast.

A poured wall typically takes more steps before it’s done: digging to frost depth, building forms, setting steel, getting a concrete truck or pump to the spot, placing and finishing, then waiting for the concrete to gain strength before stripping forms and backfilling. Backyard access matters more for poured work, since the concrete has to reach the forms.

We won’t put a national price on either; it swings too much with height, soil and access. Central Pennsylvania prices are on our retaining wall cost page.

Which wall to build

Build block if:

• It’s a yard, garden or terrace wall within the block maker’s gravity height, or an engineered wall with geogrid
• You want curves (CMHA says they’re easy with segmental units) or a choice of block sizes, textures and colors
• You’d like to build a short wall yourself

Build poured concrete if:

• You need a vertical face with no setback
• The wall is part of a structure, like a garage, stair or foundation, and an engineer is designing it
• You want a smooth or form-textured face, or plan to cover it with stone veneer

If your wall sits beside a driveway, our sample driveway retaining wall plan shows how a Groundwork Design Co. plan lays one out.

DIY or hire a pro

A short block wall on firm soil is a fair DIY job if you follow the maker’s install guide. Compaction is where DIY walls go wrong: CMHA calls for backfill compacted in lifts of 8 inches or less, and within 3 feet of the wall, only hand-operated or walk-behind equipment, preferably a plate compactor of at least 250 pounds.

Hire a pro for any wall past the IRC thresholds, any wall with a driveway, slope or building above it, and nearly any poured wall. Forms, steel and a concrete pour don’t leave room to learn on the job.

Frequently Asked Questions

Is a poured concrete retaining wall stronger than a block wall?

Both are designed for the soil they hold. A poured wall is rigid and can crack if the ground moves; a block wall is flexible and can shift without distress. Above the IRC’s limits, either one needs an engineered design.

Does a block retaining wall need a footing below the frost line?

No. CMHA says segmental walls are flexible, so the gravel leveling pad, at least 6 inches thick, doesn’t need to go below the frost line as long as the soil can carry the load.

Does a poured concrete retaining wall need a footing?

Yes. A poured wall is built on a concrete footing, and where the ground freezes that footing is normally protected from frost, usually by setting it below the local frost depth. Ask your building department what depth it wants.

How tall can a retaining wall be without an engineer?

Under IRC R404.4, up to 48 inches of retained soil, or 24 inches if the wall also resists other lateral loads, such as from a driveway above it. Local codes can be stricter.

Which is cheaper, a block or poured concrete retaining wall?

Usually block. CMHA calls segmental walls a cost-effective alternative to cast-in-place walls because they skip formwork and heavy equipment and can usually use on-site soil.

Sources: 2021 International Residential Code, R404.4 Retaining walls, ICC; 2021 International Residential Code, R403.1.4.1 Frost protection, ICC; CMHA, SRW-TEC-005: Guide to Segmental Retaining Walls; Ohio DOT 2013 Construction and Material Specifications, Item 518 Drainage of Structures (518.03, 518.05, 518.06)

Published by Muthler Landscaping & Construction, owned by Thayne Muthler (PA HIC #PA212584). How we research and check facts: editorial policy.