Tree Preservation
Tree Cabling
There are several methods used to help preserve trees by using supplemental support systems, such as cabling, bracing, guying and propping. This article focuses on cabling and provides an insight into one of the cabling techniques we use.
TREES ARE UNIQUE. SO ARE CABLING SOLUTIONS.
Trees are unique, each growing in its own weird and wonderful way. However, this uniqueness can sometimes result in weak unions or overextended limbs, especially in urban environments like Vancouver, posing potential risks to people and property. Many clients worry that tree cabling, a common preservation technique, might look unsightly, thinking it involves wrapping cables around the tree. In reality, cabling is a subtle method, often barely noticeable, with cables installed in the canopy, running individually from one limb to another. Preserving the aesthetic and value of our urban trees is a vital part of tree care, ensuring safety and maintaining the natural beauty of our city.
Why do we install cables?
Supplemental Support for Stems and Branches
There are three main reasons why we would install a cable or supplemental support system
1. Prevention – to reduce the chance of limb failure on an otherwise healthy tree that has potentially weak unions/crotches
2. Preservation – to preserve the existence of a damaged or weak tree for its amenity or aesthetic value
3. Protection – to mitigate the chance of failure in a potentially hazardous tree or one which poses a high risk e.g. if it is located over property of a frequently populated location like a park bench or footpath.
Arborist Assessment
The first step is for a professional arborist to assess the tree and determine the most appropriate hardware.
There are several different types of wire cabling devices which can be used. In this particular process we are using extra high strength cable with a Rigguy Wire Stop system.
HOW MANY CABLES ARE NEEDED?
In the simplest form cabling is essentially a single cable which is installed directly into one stem of a tree and runs to another stem. Sometimes a tree will require more cables. The cables should reduce (but not restrict) movement and stress on a tree’s weak points to help mitigate the risk of failure.
WORKING THE PLAN
Once the arborist assessment and recommendations have been given, the climber accesses the tree and locates a position at least two-thirds (2/3) between the point of weakness to the end of the branches. The point of installation is inspected to ensure that the wood is structurally sound to hold the hardware and that it is solid and large enough to provide adequate support.
It may also be necessary to carry out some end weight reduction on the limbs by selectively pruning some of the branches to help reduce the weight and stress on the weak point.
DRILLING ANCHOR HOLES
A hole just bigger than the cable is drilled directly through both stems
The cable is cut to length and thread through the holes. It is important that the cable’s pull is in direct line with the weak point to provide the most amount of structural support.
Installing the cable
A “come along” is a pulley system which is connected to the two stems and when it is pulled tight it brings the two stems closer together so that the cable can be set to the correct tension.
Setting the cable stop
The Rigguy cabling system utilizes a cone shaped wire stop which which eliminates the need for larger, more cluttered hardware and can be used in more applications as it is secured on the outside of the limb.
Tensioning the Cable System
One end of the cable is set and the wire stop is fully installed. The come along is engaged and the second end of the cable is temporarily set so that the come along can be released and the cable can be checked for the correct tension.
Getting it right. It's all in the details.
The cable should be just taut, not too slack or too tight. A too-tight cable can stress the wood fibres, causing more damage at the defect site or pulling out the hardware entirely. A too-slack cable will not effectively reduce movement or stress on the limbs.
The tension is readjusted by engaging the come along and temporarily resetting the wire stop. Once the arborist is happy with the tension the wire stop can be fully set and the finishing cap installed.
The cable is now fully installed and the job is complete and conforms to the ANSI A300 standards. In order to be effective, the cable should be checked by a qualified arborist on an annual basis to ensure there is to ensure no damage and to correct tension if required.
When should I consider cabling?
Branches that pose a potential threat to property or people may be suitable for cabling.
Tree features that may pose a higher risk of failure include: splits, decayed branch unions, or stems with included bark (see photos right and below). Multi-stemmed trees are also susceptible to breakage under the stress of wind or the weight of accumulated ice or snow.
