Partial failure
Risks
Recent partial failures will significantly compromise the strength of the tree part .
It is not uncommon to encounter partial failures of tree parts , for example the partially-failed union shown above .
Over time , the tree will usually attempt to respond to partial failures by putting on adaptive growth and woundwood . The presence of woundwood is usually a good indicator of how recently the partial failure occurred .
Older partial failures , particularly where there is evidence of adaptive growth and the formation of woundwood , may be of less concern .
Control measures
Investigate extent of failure using probing .
Conduct load and pull tests to simulate working loads on the failed part of structure .
Strap or brace the failure before access .
Load partially failed unions in compression .
Root plate lifting
Risks
Where structural roots of the tree have lifted , the tree may fail under low and unpredictable loads when the load is applied in the same direction as the lean .
Root plate lifting shows that the tree has moved in the ground and may be leaning in the direction away from the lifted roots .
If the roots are not exposed , look for cracks in the soil , a hollow sound when the ground is hit , or for a raised ‘ hump ’ of soil on the upper side of the tree . This hump of soil is a sign of soil heave , and when coupled with any lean of the main trunk may be a key indicator of root instability .
Control measures
Investigate extent of root plate lift ; try to estimate how long the tree has been in this condition .
Conduct pull tests to simulate the working loads which will be placed on the tree .
Guy or brace tree before access .
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