Cribbing (also called a “box crib”) is a popular practice among aerial lift operators, construction foreman, and other job site workers, and it is used in a variety of work situations.
What Is Cribbing in Construction?
Cribbing refers to a temporary work structure used to support heavy objects in construction. The process of cribbing involves building a temporary wooden structure to support heavy machinery. However, this process can be dangerous if workers don’t know the proper cribbing techniques.
Safe Cribbing Techniques You Need to Know
If you or your employees use cribbing and aerial lifts, knowing the basics of cribbing safely is crucial to prevent accidents that can lead to serious injuries, fatalities, and equipment damage.
Let’s take a look at different cribbing construction methods, cribbing material, safety for crane cribbing requirements, and more.
Wood Cribbing Construction 101
The use of cribbing is essential for many extrication operations. Its most common use is to stabilize large objects and heavy equipment.
Stability is important with any type of cribbing material. Cribbing should also be free from paint or finishes. Pieces of wood that are 2×2 and 4×4 are common for use with cribbing construction work.
The actual work of cribbing involves multiple pieces of wood that are laid on their side and crossed over each other. This technique spreads the load and creates multiple load transfer surfaces. This type of cribbing structure also offers lateral stability.
Here are a few basic rules for wood cribbing construction:
– The height should be no greater than three times the width.
– The overhang at the corners should be no less than 4 in.
– The weight limit for a 44 cribbing structure is about 24,000 lbs., and for a 6’×6′ structure, it’s about 60,000 lbs.
Wood cribbing blocks used at each level increase the number of support points. That way, they improve a crib tower’s overall strength and stability.
How to Properly Use Cribbing
In most instances, cribbing is used to support an extra-large piece of industrial equipment. At other times, it’s used to improve the angle for hoisting or lifting materials. Cribbing is also used to improve stability on unstable surfaces.
When selecting the materials for wood cribbing construction, look for these qualities:
• Physically capable of handling heavy loads
• No cracks, deformations, rot, or bent, worn, or damaged parts
• Larger than the foot of the outrigger
• Enough thickness, width, and length to provide stability
• No oil, grease, or debris that can cause slippage
In addition, all workers involved in wood cribbing construction must wear personal protective equipment (PPE), such as:
• Steel-toed boots
• Eye protection
PPE is one of the key crane cribbing requirements as well. Thus, crane cribbing should only be completed if workers are wearing proper PPE.
A Closer Look at Cribbing Construction Best Practices
Cribbing construction best practices include:
✓ Set the cribbing materials on firm, level ground
✓ Ensure no debris is under the cribbing or blocking
✓ Place the cribbing structure directly beneath the outrigger
✓ Inspect the cribbing during operation
✓ Ensure the cribbing is no taller than twice the width of the blocking base
To calculate the correct blocking size to use, follow these rules:
Rule of 5: Take the maximum lifting capacity in tons of the unit and divide it by 5
Rule of 3: Take the square footage of a crane’s floats and multiply it by 3
Either of these calculations can provide you with the correct blocking size to use.
Which Cribbing Material Is the Best Option?
Wood is the preferred cribbing material, but plastic is also popular for cribbing. In rare cases, steel may also be utilized as a cribbing material.
Plastic and steel may be used for cribbing due to the fact that they are sturdier and less susceptible to chemical corrosion than wood. But for most purposes, wood works well for cribbing.
What Is the Best Type of Wood Cribbing?
Wood cribbing blocks often consist of softwoods like Douglas Fir or Southern Pine. To determine the strength of wood cribbing blocks, it is important to evaluate several factors, including:
– Wood species
– Moisture content
The strength of wood is predicated on the direction of loading, which is either parallel or perpendicular to the grain. For example, Douglas Fir or Southern Pine woods have allowable bearing stress to the longitudinal grain (parallel to the grain) of approximately 650 psi.
Comparatively, these same types of wood generally have allowable bearing stress to the cross grain (perpendicular to the grain) that varies from 300 psi to 700 psi.
How to Tell If Wood Cribbing Is Defective
If wood cribbing is under too much weight, it has built-in safeguards that indicate if it is overloaded. In this instance, wood cribbing may start to crush or make a “groaning” noise as additional weight is placed on it.
Regardless of which type of material you use for cribbing, it’s important to maintain stability. You should also follow OSHA Crane Standard 1926 for crane pad and outrigger pad operators.
OSHA Crane Standard 1926 requirements include:
1400: Explains who should use outrigger pads, crane mats, and other supporting materials.
1401:Defines safe ground conditions and supporting materials.
1402:Describes how to analyze and prepare ground prior to using supporting materials.
To learn OSHA safety requirements for cribbing, a training program is ideal. By participating in a training program, you can gain insights into OSHA Crane Standard 1926 and many other OSHA crane cribbing safety regulations.
Wood Cribbing Worker Safety
For aerial lift operators, cribbing has to be undertaken with extra caution. Given the top-heavy loads and height of some aerial lifts, wood cribbing construction should only be done under professional, certified supervision. This includes cribbing with scissor lifts and common aerial work platforms.
The proper training is essential to ensure operators and workers involved with cribbing construction and aerial lifts are prepared to recognize and avoid hazards. Aerial lift training teaches operators how to safely perform tasks on and off cribbing.
Wood Cribbing Safety Factors to Consider
Stable, flexible woods should be used for cribbing. These woods can support heavy weights; plus, they are more prone than other woods to creak or make other noises if too much weight is present.
If cribbing makes noise, it should be replaced immediately. The longer the noise is present, the more likely it becomes that the cribbing is defective. If you do not address the issue, the cribbing could shatter, which could break your equipment or harm your workers.
Brittle woods are susceptible to splitting or snapping under heavy weight. As such, these woods should always be avoided for cribbing.
When it comes to wood cribbing safety, training is essential as well. Workers who understand the risks associated with cribbing can identify and address dangers before they escalate. These workers will also know how to develop and execute crane cribbing requirements.
Crane Cribbing Requirements
For outrigger pads, offshore rigging, heavy-duty rigging, and other crane-based procedures, always follow basic cribbing construction methods. You should always follow the crane manufacturer’s recommended procedures for your crane cribbing requirements as well.
The Do’s and Don’ts When Using Cribbing to Bolster Your Aerial Lift
Crane cribbing do’s and don’ts include:
• Consult with your lift’s operation manual, find out what it says about cribbing, and ensure temporary cribbing follows your manual’s guidelines.
• Ensure that your cribbing structure is sturdy and stable.
• Select a material for construction cribbing that is solid, straight, and free of flaws.
• Ensure the cribbing construction structure is properly stacked to spread the load well and distribute the weight of the object.
• Wear PPE like work gloves, a helmet, and a reflective vest any time you work with cribbing.
• Develop and implement a cribbing stabilization plan.
• Use cribbing or another tool to place cribbing.
• Understand the work surface (grass, snow, etc.) and ensure that your lift and cribbing can remain stable on this surface.
• Conduct a walk-through after cribbing stabilization is complete to verify that all points where cribbing stacks are located are supporting the object that needs to be stabilized.
• Ignore the weather, as rain, mud, ice, and other elements can impact your lift’s ability to maneuver on cribbing.
• Structure cribbing on surfaces that are painted or finished.
• Stack cribbing more than three times its width.
• Forget to use a safety harness.
• Pull all cribbing out from beneath a supported load at once.
• Keep your hands and body in the fall area when placing cribbing.
• Place cribbing on top of an airbag.
Finally, it is important to remember that whenever an employee works with aerial lifts or scissor lifts, there are risks involved, and this applies to construction cribbing as well.
How Can Employers Protect Workers Against Construction Cribbing Risks?
According to OSHA, it’s up to employers to ensure workers have received the training they need to:
✓ Operate the controls of an aerial lift
✓ Inspect equipment
✓ Assess a work environment
✓ Perform cribbing and other tasks safely
Aerial lift certification training should teach workers involved with construction cribbing the safest ways to work with cribbing on an aerial lift or scissor lift. It should also teach these workers how to keep a structure sturdy and balanced and eliminate dangers.
Sign Up for Aerial Lift Certification Training from AerialLiftCertification.com
Proper construction cribbing falls right in line with proper aerial lift safety. For the best aerial work platform safety training, only one provider gives you OSHA-compliant instruction, flexible course scheduling, and affordable pricing — AerialLiftCertification.com. To find out more about our aerial lift certification or to sign up for our training program, please contact us online or call us today at (888) 278-8896.