When stabilization matters, cribbing is only as good as the performance limits placed on it. If you’re working in fire/rescue, construction, utilities, or heavy equipment maintenance, load ratings and cribbing performance factors are critical to safe and effective operations. Failure to respect these limits can result in equipment damage, collapse, injury, or worse.
Understanding Load Ratings
Every stabilization cribbing block—whether plastic composite, hardwood, or another material—comes with a working load limit (WLL). This is the maximum weight the cribbing can withstand under proper conditions and within its intended design.
- Composite cribbing (plastic, engineered materials): Typically tested and rated between 800–1,200 PSI, with some blocks supporting 60,000+ lbs. under optimal conditions.
- Wood cribbing: Has more variable ratings depending on species, environmental factors, pest damage and internal condition (cracks and knots). Wood cribbing, no matter what the species can be unpredictable and consistently unreliable.
Here are a few example references from our own Working Load Guide:
- Heavy-duty blocks such as The Slab® are rated at 242,000 lbs. WLL.
- Medium-duty products like the Super Crib® are rated at 110,000 lbs. WLL.
- Light-duty cribbing such as the new 44HDC -18™ supports 70,000 lbs. per block.
Key Factors That Impact Vehicle Stabilization Cribbing Performance
Even when cribbing is rated correctly, setup and environment directly affect its performance:
Contact Points
More points of contact = greater stability. A nine-point box crib is stronger and more reliable than ad-hoc or uneven stacks.
Height-to-Width Ratio
The US Army Corps of Engineers recommends a 3:1 height-to-width ratio for crib stacks. Taller stacks should be widened with base layers or pads to avoid tipping.
Corner Overlap
Maintaining at least 4 inches of overlap at cribbing corners ensures the load is transferred properly through the stack.
Load Distribution
Published ratings assume weight is spread evenly. Point loading significantly reduces capacity and creates a high risk of failure.
Ground Conditions
Always start with a firm, level base. Use top and bottom cribbing pads (e.g., Slab Pads or ModPads®) to distribute the load.
Deformation in Service
Wood may crush or lose 10–20% of its height before failing, serving as a warning sign but failure is catastrophic, meaning there is no forgiveness when the wood is overloaded.
Plastic cribs deform or squish slowly, which can provide safer warning characteristics in overload conditions. Also, pyramid facades assist in understanding wear and tear of the block to remove it from service.
Wood vs. Composite Cribbing
Many operations still rely on wood cribbing, but composite (recycled plastic) stabilization cribbing offers some major differences:
| Factor | Wood Cribbing | Composite Cribbing |
|---|---|---|
| Durability | Prone to cracking, rot, moisture absorption, and contamination | Non-porous, impervious to most industrial chemicals, rot resistant |
| Safety | Splinters, unpredictable crush | Splinter-free, uniform performance |
| Load Capacity | Depends on wood quality | Consistent 800–1,200 PSI ratings |
| Maintenance | Absorbs oils and biohazards, harder to clean | Washable and can be easily decontaminated |
| Cost | Lower initial purchase | Higher up front, longer lifespan = long-term value |
Best Practices for Safe Use
- Always read your equipment owner’s manual or your company’s standard operation procedures to ensure safe cribbing techniques.
- Adhere to the Turtle Plastics’ published working load limit (WLL) of the blocks in use.
- Keep height-to-width ratio at or below 3:1 (no more than 3x the base).
- Use a solid, level base—pads when needed.
- Ensure even contact and overlap in every stack to avoid point source loading.
- Inspect cribbing before use; retire any cracked, crushed, or excessively worn blocks.
- Avoid modifications: never drill, cut, or alter cribbing blocks.
Final Thoughts
In stabilization work, every block matters. Relying on cribbing with known load ratings and proven performance is not optional—it’s life-saving.
Contact Turtle Plastics today to learn how our vehicle stabilization cribbing solutions can improve safety, durability, and sustainability in your operations.
