Mafia Blocks: Sizes, Weight and Uses for Big Concrete Blocks

Mafia blocks are large precast concrete blocks, often made from leftover ready-mix concrete poured into forms at the end of the day. They're also called lego blocks, ecology blocks, jersey-style blocks or waste blocks. Many have a raised knob on top and a matching notch underneath so they stack and interlock like giant toy bricks. A standard full block is about 2 x 2 x 6 feet and weighs roughly 3,600 pounds, so you set them with a machine, not by hand.

Sizes and weights

Concrete weighs about 150 pounds per cubic foot, so weight follows size:

Block size (H x W x L)	Volume	Approx. weight
2 x 2 x 6 ft (full)	24 cu ft	about 3,600 lb
2 x 2 x 3 ft (half)	12 cu ft	about 1,800 lb
2 x 2 x 4 ft	16 cu ft	about 2,400 lb
2.5 x 2.5 x 5 ft	about 31 cu ft	about 4,700 lb

Sizes vary by producer. Some blocks have lifting loops cast in; others are moved with a clamp or forks.

Common uses

• Bulk material bins for mulch, gravel, salt or sand
• Retaining walls on farms, commercial sites and large properties
• Barriers to stop vehicles or block access roads
• Erosion and slope control along drainage channels
• Windbreaks and ballast for temporary structures

Retaining walls with mafia blocks

Mafia blocks make strong walls quickly, but they're still a retaining wall and follow the same rules:

1. Base: excavate to firm soil and compact 6 inches or more of crushed stone, level side to side.
2. Setback: many walls are stepped back a few inches per course, or the blocks have a built-in setback, so the wall leans into the hill.
3. Drainage: backfill behind the wall with clean gravel and a perforated drain pipe at the base. Saturated soil can push even 3,600-pound blocks.
4. Height limits: walls over about 4 feet of retained soil usually need an engineer's design and a permit, and tall block walls may need geogrid reinforcement in the backfill. See the code discussion in natural stone retaining wall.

Getting and placing them

• Where to buy: ready-mix concrete plants and precast yards. Price per block varies a lot by region, size and whether delivery is included.
• Equipment: a skid steer can handle half blocks; full blocks generally need an excavator, a large loader or a boom truck. Many suppliers deliver and set blocks with a crane truck.
• Ground pressure: loaded trucks and machines can crack driveways and damage septic systems and buried lines. Call 811 and plan the route.
• Safety: never stand between a suspended block and anything solid. Use rated lifting gear and keep people clear of the swing area.

Pros and cons

Pros	Cons
Fast to build; no mortar or cure time	Heavy equipment required
Very strong and stable	Industrial look; plain gray concrete
Can be moved and reused	Uneven quality between producers
Often inexpensive per foot of wall	Tall walls still need engineering

If you want the look of stone instead, consider facing a block wall with plantings, or use natural stone and landscape boulders for visible areas.