Building a concrete block wall: base and sand guide
A concrete block wall lasts when the footing and base are right. Most of what we deliver is what's underneath and around the block.
- Footing
- Concrete footing below frost line
- Base
- Compacted road base under the footing area
- Drainage
- Gravel backfill behind the wall
- Joints
- Masonry sand or as specified
The footing
A block wall needs a reinforced concrete footing, typically twice the wall thickness and below local frost depth. The footing must be level — a block wall follows every dip and rise. In Central Texas clay, a wider footing helps resist soil movement from wet and dry cycles.
Base and subgrade
Before the footing, compact the subgrade and lay road base where the ground is soft or uneven. Good compaction under the footing area prevents settling that cracks the wall. On slopes, step the base in layers rather than pouring on a slope.
Drainage behind the wall
Water buildup behind a block wall causes the single most common failure. Backfill with gravel and install drainage at the base so water doesn't press on the wall. Sand can be used as a leveling or filter layer, but gravel is the main drainage material.
Joints and fill
Core-fill the blocks with concrete where the design calls for it. Use masonry or concrete sand for bedding or joint fill where specified. Don't substitute sand for structural fill — follow the engineer's or manufacturer's spec.
About the blocks
We don't sell concrete blocks. We deliver the road base, gravel and sand that go under and behind the wall — the heavy bulk materials that make the wall stand up.
Materials we deliver for this project
Get the bulk materials delivered by the ton across Austin and Central Texas.