What is resistance drilling?
Resistance drilling has been around for several decades (nearly 40 years) and has been used to determine the strength of wood. It uses a very small diameter drill bit (about 1.5mm) spinning at incredibly high resolutions. While it is drilling into the tree it measures the resistance that the wood provides. The stronger the wood the more resistance. The softer or more decayed the wood is then the less resistance. I should note here that you cannot always differentiate between decayed wood and cavities, both would indicate (low resistance). So don’t be surprised when your tree comes down and there is no cavity. You are only able to determine cracks (the way they appear on the graph) or sound wood with high strength (High Resistance).
Why is resistance drilling useful?
Resistance drilling is useful when you have trees near a client’s home that possess moderate to high risk (a target with a high occupancy rate: such as a home). This may be a tree that the customer appreciates but is concerned about. If you sound the tree, and you hear a hollow resonance during a basic tree risk assessment you may suggest further testing with a resistance drill, which will provide the client with more information about where the decay is located within the tree. Please note that I mentioned the location of the decay. Decay is present in most trees. The location of the decay is important to the strength of the tree. Decay located at the center of the tree is better than if that decay was located on the side of the tree. Additionally, the ratio of decay to high-resistance wood is also important. None of these above statements can be clearly understood unless you are using a resistance drill.
How do I know if resistance drilling is right for my tree?
If you have a tree(s) near your home, playset, garage, shed, or any public gathering space you should have a certified arborist with a Tree Risk Assessment Qualification come out and conduct a Level 2: Basic Assessment to determine if a high level of assessment is necessary. If the arborist hears a cavity, notes fungal bodies, or sees woodpecker damage it may prompt a Level 3 Advanced Assessment. The arborist information will provide the necessary information to plan the future of your tree.
Remember, all trees pose risk even healthy and seemingly perfect ones. The only time you have zero risk is when you have the tree removed. However, trees add value to your property and community. Getting more information about your trees will help you retain your property value and keep you safe.