Tree Rigging - Ropes, Rigging Hardware, and Techniques

Why this matters

Tree rigging is the use of ropes, pulleys, and friction devices to safely lower branches, limbs, and tree sections from height. Without proper rigging, large tree work requires either dropping the material (often impossible due to structures, plantings, or property below) or significant ground-side cleanup. Rigging adds capability AND safety - a properly rigged section descends in controlled motion rather than free-falling. This is one of the most consequential technical skills in tree work.

Why we rig

Three primary reasons:

1. Property protection: structures, landscaping, fences below the cut
2. Worker safety: large sections lowered controlled rather than dropped
3. Customer expectation: professional service includes clean removal

A 200-pound branch dropped from 30 feet creates significant impact damage and is dangerous to ground crew. The same branch lowered with rigging arrives safely on the ground.

Required equipment

Climbing rope vs. rigging rope

These are different:

Never use the climbing rope for rigging. Different strength specifications.

Common rigging rope materials

Standard tree rigging: 3/4 inch or 1/2 inch double-braided nylon or polyester. Capacity in the thousands of pounds.

Pulleys and hardware

A complete rigging system includes all of these. Each has specific load ratings and uses.

Lowering devices

The lowering device handles the friction needed to control the descent:

• Hobbs Lowering Device: simple metal device that wraps the rope around a drum
• Port-a-Wrap (Stein): similar concept; controls descent rate
• Cumberland's design: another lowering device

The ground worker controls the descent by adjusting friction on the rope at the lowering device. Slack out = faster descent; pull in = slower.

Basic rigging procedure

Step 1: Plan the cut and the rigging

Before any cutting:

1. Identify the section to be removed
2. Identify the tie-off point (basal anchor)
3. Plan the cut location
4. Identify the landing zone
5. Verify the rigging can handle the load

Step 2: Set the rigging point (the block), ABOVE the cut

Two separate anchors are involved and mixing them up is the most common setup error. The rigging point carries the block and goes ABOVE the piece being cut, on the spar being worked, so the block catches the load above its own centre of gravity. The base anchor is at ground level and carries the lowering device.

1. Choose sound wood above the cut: no decay, no codominant union, adequate diameter for the load
2. Wrap a sling or a purpose-made block sling around it, with a friction saver or block sling protecting the bark
3. Verify the stem above the block can take the load (a block on a weak leader loads it in a direction it never grew for)
4. Hang the block on the sling

Step 3: Set the rope

1. Reeve the rigging rope through the block
2. Run one leg down to the lowering device at the base
3. Take the other leg to the piece and tie it ABOVE the piece's centre of gravity, so the piece hangs controlled rather than swinging end over end
4. Use an appropriate hitch (running bowline dressed with half hitches, or clove hitch plus marl on a long limb)

Step 4: Setup at the ground

1. Lowering device attached to a separate anchor (often a different tree)
2. Rope passes through the lowering device
3. Ground worker takes position behind / beside the device
4. Verify communication signals with the climber / sawyer

Step 5: Make the cut

1. The climber positions clear of the cut + the lowering path
2. Make the cut
3. The branch / section drops slightly, taking tension on the rope
4. The lowering device begins paying out controlled rope
5. The branch descends to the ground at controlled speed
6. Ground crew receives + clears the section

Step 6: Repeat for additional sections

Multiple cuts in a tree typically require multiple rigging setups; plan ahead.

Knots and hitches

For tree rigging, common knots:

Practice these knots cold; tying them under pressure is the test.

Load ratings

Every rigging component has a Working Load Limit (WLL):

• Rope: typically 1/8 of breaking strength (8x safety factor)
• Hardware: 1/5 of breaking strength (5x safety factor)
• Slings: 1/5 of breaking strength (5x safety factor)

The rated load is the MAXIMUM the component should bear. Exceeding the WLL risks failure.

A green hardwood log 18 to 24 inches in diameter weighs roughly 100-200 pounds per foot (green hardwood runs about 55 to 62 pounds per cubic foot); a 20-foot section of that size is 2,000-4,000 pounds. A 4-inch limb, by contrast, is only about 5 pounds per foot. Measure the diameter before you size the rigging; components must match the real weight.

The piece weight is not the load. A rigged piece is dropped, caught, and decelerated, and the peak force at the block and the rope is a multiple of the static weight, not the static weight plus a bit. Published arborist rigging guidance puts that multiple at two or more on a controlled let-run and much higher on a snatched piece with a short drop onto a tight line, because the shorter the drop and the less rope in the system to stretch, the harder the catch. Letting the piece run on the friction device is what keeps that peak down, and it is a technique, not a component.

So the calculation is not:

• Component WLL ≥ estimated piece weight × 1.5

It is:

• Component WLL ≥ estimated piece weight × the dynamic factor for the way this piece will actually be caught

A 1.5 multiplier is not a shock-load allowance and will not cover one. Where the number has to be right, take the dynamic factor from the rope and hardware manufacturer's rigging data and the ISA Best Management Practices for rigging, size every component in the chain (rope, block, sling, hardware, and the anchor stem itself) against the result, and where the piece is large enough that the arithmetic is close, make it smaller or take it with a crane.

Friction in rigging

Friction is the controlled descent:

• Lowering device generates friction
• Friction converts kinetic energy (falling load) to heat (rope + device)
• Heat dissipates safely (within limits)
• Excessive friction may damage the rope; insufficient friction means uncontrolled descent

Adjust friction based on:

• Load weight (heavier = more friction needed)
• Drop height (longer drop = more friction)
• Ground worker's strength
• Rope condition

Climber-side rigging

The climber-side rigging:

The climber rigs from the position; the ground crew receives.

Tree species considerations

Different tree species behave differently:

Crane-assisted rigging

For large trees:

• The crane replaces the tree as the anchor. That is the whole point. On a decayed or hollow spar with no sound anchor point above the cut, a crane is often the only safe way to take the wood
• Every pick is weighed before it is cut. The signal person estimates the piece by species density and dimension, confirms it against the crane's load chart at that radius, and confirms the sling rating. A piece that turns out heavier than planned is the failure mode that hurts people
• The climber cuts; the operator lifts; one person signals. One voice, agreed hand signals or radio, and an abort word everyone knows. No side conversations during a pick
• Slings and the pick point go on before the cut, with the line snugged and the pick weight taken gradually so the wood is supported before it is released
• Tag lines control rotation. Two on long sections, ground crew clear of the travel path
• The drop zone is cleared and marked, and nobody stands under a suspended load or inside the swing radius, ever
• Set the crane on level, compacted ground with mats and full outrigger extension, clear of the utility clearance envelope. The setup takes longer than anyone likes and it is not the place to save time

Crane removal is a different discipline from conventional rigging, not a bigger version of it. If the crew has not run crane picks before, bring in someone who has for the first several jobs.

References

• ANSI Z133 (Safety Requirements for Arboricultural Operations)
• ANSI A300 (Tree Care Standards)
• TCIA (Tree Care Industry Association) rigging training
• ISA (International Society of Arboriculture) BMP for Rigging
• Manufacturer documentation for rope + hardware
• Manuall internal: Chainsaw Safety, Tree Removal Service SOP, Climbing Safety