Tree Felling Notches: Open Face vs. Humbolt (Guide)
An open-face notch has a wide 70–90° opening that can help a sound hinge stay engaged as a tree starts to fall. A Humboldt notch reverses the usual notch geometry, with a horizontal upper cut and angled lower cut. Neither notch makes an unsafe tree safe. Tree condition, lean, landing area, training, and local rules decide whether DIY felling is appropriate.
A tree can look simple from the ground and still behave in ways you cannot predict from its appearance. A weak hinge, hidden decay, wind, or a leaning trunk can change the fall in seconds. That is why notch choice is only one part of a felling plan, not a shortcut to one.
I have seen even skilled crews pause when a tree’s lean, crown, or defects do not match the planned fall. If you have not been trained to assess those hazards and operate a saw, do not try to learn by cutting a standing tree. Use this guide to understand the terms and compare methods, then bring in a qualified feller when the tree presents risk.
What the notch and hinge do
A felling notch, also called an undercut, is a cut that helps set the tree’s intended direction of fall. The hinge is the strip of uncut wood between the notch and the back cut. It helps guide the tree, but it is not a mechanical guarantee and can fail if the wood or forces are not understood.
The notch, hinge, back cut, and tree condition work together. A tree may fall away from the intended direction if the hinge is uneven, the trunk is decayed, or the crown is caught in another tree. No notch design can overcome every defect or force.
For covered logging operations, OSHA’s logging rule limits undercut depth to no more than one-third of the tree’s diameter. That requirement is not a complete felling plan, nor does it replace training or a site-specific risk assessment. A hinge around 10% of the diameter is a common planning reference, not a universal safe dimension. Species, decay, lean, and trunk shape can change what is suitable.
Open-face versus Humboldt notch
An open-face notch usually has a wide opening, often about 70–90°. Its upper and lower cuts meet to form the opening. A Humboldt notch reverses the conventional notch’s geometry: its upper cut is horizontal and its lower cut is angled. The choice depends on the job and the operator’s plan.
| Feature | Open-face notch | Humboldt notch |
|---|---|---|
| Basic geometry | Wide opening, typically 70–90° | Horizontal upper cut with angled lower cut |
| Main consideration | Wide opening can help keep the hinge engaged during early fall | Reverse geometry may suit some site or stump-value needs |
| Choice depends on | Tree condition, fall plan, terrain, and operator training | The same factors, plus the reason for choosing its stump geometry |
| Not a substitute for | Sound hinge, hazard assessment, and a safe landing zone | Sound hinge, hazard assessment, and a safe landing zone |
A wide opening can allow the tree to rotate farther before the notch closes, which may help the hinge guide the fall. That benefit depends on sound wood and correct execution. The Humboldt notch is not simply a safer or better version; its reverse geometry serves a different purpose and must match the fall plan.
Do not choose based on a diagram alone. If a tree leans toward a building, has a split trunk, or carries a heavy crown over a target, the right answer may be to stop and hire a professional rather than switch notch styles.
Choosing a notch for the tree and site
A suitable notch is selected only after assessing the tree and the full work area. That means considering the tree’s lean, crown, species, defects, terrain, wind, overhead hazards, and the landing zone. If any of those factors are uncertain, a trained tree-felling professional should assess the job.
A straight-looking trunk can still have a heavy crown on one side or a hidden defect near the base. Lean is not the only force that affects a fall. Wind and nearby trees can also change how a crown moves. Before any cutting begins, the landing area and escape routes must be clear, and people must be kept out of the hazard zone.
A notch is intended to guide a fall, not force one. Never improvise the notch or back-cut geometry on a leaning, damaged, or unfamiliar tree. Do not cut through the hinge. Those choices can remove the control the felling plan depends on.
Field decision scenarios
These are decision examples, not cutting instructions. They show why notch choice should follow a site assessment rather than a preference for one shape.
- Sound tree with a clear landing area: A qualified operator may consider an open-face notch where the wide opening suits the fall plan and the tree’s condition.
- Job with a specific stump-value requirement: A trained operator may consider a Humboldt notch if its reverse geometry suits the site and the planned work.
- Severe lean, trunk crack, or butt defect: Stop. The risk of an uncontrolled split or fall makes this a professional job.
- Tree near a home, road, power line, or public area: Do not treat a notch choice as enough protection. Use qualified help and follow applicable rules.
In field work, I have seen small differences in lean or crown balance change a plan. That is why a notch comparison cannot replace an on-site assessment.
Equipment setup and felling-site safety
Chainsaw felling requires training, suitable protective equipment, a working saw, and a controlled site. A qualified operator should assess the hazards before starting. If you cannot establish a clear landing area, keep people away, and plan an escape route, do not fell the tree.
Wear a helmet, eye and face protection, hearing protection, chainsaw-resistant leg protection, gloves, and suitable boots. Inspect the saw, chain brake, throttle lockout, chain catcher, bar, chain tension, and oiling system as the manufacturer directs. Follow current ANSI Z133 requirements and applicable law. OSHA 29 CFR 1910.266 applies to covered logging work; it is not a substitute for arboricultural training or a job-specific hazard assessment.
A falling tree can strike nearby trees, rebound, or send branches down after the trunk begins moving. The operator and any crew need a clear communication plan and an exclusion zone that keeps others away. Do not fell alone, work above shoulder height, or operate in an uncontrolled public or crew area.
A barbers chair is a dangerous split up the trunk that can occur when a stem under heavy lean or tension fails before the hinge controls the fall. Severe lean, cracks, butt damage, or signs of compression and tension are reasons to stop and call a professional with appropriate equipment and a plan.
Chainsaw inspection, sharpening, and manufacturer settings
A sharp, correctly set up saw is easier to control than one with a dull or mismatched chain, but maintenance does not make an unsafe felling job safe. Match the saw, bar, and chain to the manufacturer’s approved combinations. Check the exact manual for setup and service details.
There is no universal bar-length-to-engine-size ratio, fuel mix, chain specification, raker setting, or RPM value. Fuel ratio, chain pitch and gauge, drive-link count, bar oil, and idle or full-throttle settings vary by model and chain. Do not assume a common fuel mix or copy a generic tuning figure.
A longer bar increases leverage and cutting demand. Use only a bar within the saw maker’s approved range. Keep the chain sharp and correctly tensioned as the manual directs. If the saw pulls, cuts poorly, or behaves differently than expected, stop and inspect it rather than forcing the cut.
Post-use cleaning and safe fuel handling
After work, secure the saw and follow its manual for shutdown, cooling, cleaning, and storage. Refuel only when the saw has cooled and is away from ignition sources. Routine care protects the equipment, but never service a running saw or handle fuel near heat or flame.
Once the saw is safe to handle, inspect and clean the air filter, bar groove, oil holes, clutch cover, and chain as directed by the manufacturer. Check for damage before putting the saw away. Store fuel in approved containers and follow product labels and local rules.
Conclusion
The open-face notch and Humboldt notch differ in geometry and may suit different plans. An open face uses a wide opening, commonly 70–90°; a Humboldt notch has a horizontal upper cut and angled lower cut. The right choice depends on tree condition, lean, terrain, landing zone, and operator training. If the tree is defective, strongly leaning, or near people or property, do not attempt DIY felling.
FAQ
Which notch is safer, open-face or Humboldt?
Neither is always safer. An open-face notch has a wide opening that can help keep the hinge engaged as the tree starts to fall. A Humboldt notch may suit other site needs. Tree condition, training, and the fall plan matter more than the name of the notch.
What is the usual opening angle for an open-face notch?
A common target is 70–90°. That range is not a guarantee of control, and it does not replace a trained operator’s assessment of the tree and work area.
What is a Humboldt notch?
A Humboldt notch reverses conventional notch geometry. It has a horizontal upper cut and an angled lower cut. It is not interchangeable with an open-face notch; the intended fall direction and site plan must guide the choice.
How deep should a felling notch be?
For covered logging operations, OSHA limits undercut depth to no more than one-third of the tree’s diameter. This is a regulatory limit, not a recommended target for every tree or a complete cutting plan.
How wide should the hinge be?
About 10% of the tree’s diameter is a common planning reference, not a universal rule. Tree condition, species, decay, lean, and shape affect the plan. Never cut through the hinge.
Can I use a Humboldt notch on a leaning tree?
Do not use notch geometry to manage a severe or uncertain lean without professional assessment. A leaning or tensioned tree can split or fall unpredictably. Stop and use a qualified tree-felling professional.
What causes a barber chair?
A barber chair is a split up the trunk that can occur when a heavily leaning or tensioned stem fails before the hinge controls the fall. Treat severe lean, cracks, and trunk defects as high-risk warning signs.
Does OSHA’s logging rule apply to every homeowner?
OSHA 29 CFR 1910.266 applies to covered logging work. Homeowners should still follow applicable laws and safe practices, but the rule is not a substitute for proper training or a job-specific hazard assessment.
Can a longer chainsaw bar make felling easier?
Not necessarily. A longer bar increases leverage and cutting demand. Use only a bar approved for the exact saw model, and follow the manufacturer’s specifications for the bar and chain.
Is a notch enough to control a tree’s fall?
No. A notch is one part of a felling plan. Lean, defects, wind, crown balance, terrain, and nearby hazards can affect the result. If you cannot assess those factors, hire a qualified professional.
(This article was written by one of our staff writers, Julian Barrett. Visit our Meet the Team page.)
