From across a job site, large precast blocks all look alike. The difference is inside: some are solid concrete all the way through, and some, like Verti-Block, are hollow and get filled with stone once they are set. That one choice changes trucking, picks, drainage and the steps your crew follows.
Two ways to build a heavy block
A retaining wall block needs weight. A solid unit arrives at full weight, all of it cast concrete. A hollow-core unit arrives lighter and becomes heavy on site: crushed stone goes into its cores as each course is set, adding weight and creating a drain at the same time.
Where the weight comes from
| Weight | Design unit weight | |
|---|---|---|
| Concrete block (as delivered) | About 1,760 lb | 142 pcf |
| Crushed stone in the cores | About 1,280 lb | 110 pcf |
| Block and stone together (as designed) | About 3,035 lb | 126 pcf |
In plain terms Almost half the weight of a finished Verti-Block wall comes from local stone placed on site, not from concrete hauled on a truck.
Trucking and picks
Because hollow-core units ship without their fill, more wall fits on each truck. A Verti-Block truckload carries 304 sq ft of wall face, about double the face area per haul compared with solid large-format block. That means fewer deliveries into a tight site or work zone. Each standard unit covers 8 sq ft of wall face in one pick with an excavator and a block grab.
Drainage
Every retaining wall design assumes the soil behind it is drained. With a solid unit, drainage has to come from a separate aggregate zone placed behind the wall. With a hollow-core unit, the stone in the cores forms a drain the full height of the wall, and a perforated pipe at the base, filter fabric and surface grading complete the system.
The trade-offs, honestly
- Core fill is a step: hollow-core walls need clean crushed stone on site and a crew filling cores as each course goes up. Solid units skip that step.
- Stone delivery: the core stone is a separate material to order and stage, usually from a local quarry.
- What you get for it: lighter units to truck and set, more wall per truckload, and drainage built into the wall itself.
What to compare between any two systems
- Published gravity heights for your soil and loading, without geogrid.
- Unit weight, and the equipment it takes to set it.
- Wall face per pick and per truckload.
- How the units lock together and set the batter.
- Where the water goes, and which details cover it.
- Local supply, lead time and design support.
For the full checklist, see how to choose precast retaining wall blocks. For every Verti-Block number, see the design data.
Source: Verti-Crete Design Manual, Release 4.1 (block detail sheet BD-02), Verti-Block product data sheets, and Natrix Precast project experience (marked "in our experience").
