After an absence of nearly two years, during which time there was an extensive review, the new Lantra Mortgage course was launched at Lantra House on Tuesday 30th January 2018. The new course brought together the best of courses run by Myerscough College, the Consulting Arborist Society and Tree Life.
The launch was different to future courses, as it was co-delivered by Dr. Dealga O’Callaghan, Lead Assessor, and Dr. Jon Heuch, both of whom had given considerably to the development of course material. Giles Mercer, who has extensive experience in soils and vegetation, and Bob Widd, who has processed many subsidence cases, also contributed, the latter leading on a case study scenario. Giles and Bob will be leading on the next course at Myerscough College on 29th May 2018.
Dealga introduced the course and explained the need for the review and how the process for dealing with subsidence cases has changed since he first wrote training on this subject in the early 1990s. He explored subsidence and the difference between this and settlement and heave. He explored the role of clay soil in the process, and the variable patterns of shrinkable clay. Illustrations of subsidence cases were shown, including one which caused damage to a Georgian property and was linked to an ornamental tree. The problems, he emphasised, are not necessarily linked to larger trees!
There was exploration of how subsidence actually happens and the relationship to annual rainfall. It is interesting that in 2017, the dry spring began to cause problems, and there were concerns of an increase in claims, a threat which subsided with the wet summer.
Dealga went on to explore the species-specific relationship between trees and subsidence. For the past two decades, trees were attributed to be causing problems based on the volume of water they could absorb, and also the distance roots were round to have spread. Neither measure is reliable. He explained that the distance measure was an erroneous connection which has not yet been properly disseminated. Regarding water uptake, the problem is not volume but depth of extraction. A mature Beech tree can extract the same volume of water as a mature oak. However, the Beech, being shallow rooted, does not cause problems, whereas the oak can. Updated data on influencing distances was presented.
There was exploration of how to manage implicated trees. A ‘scorched earth policy’ is not desirable, and if a tree and building have co-existed for many years, it is unlikely there will be a problem. There was emphasis that pruning does not resolve subsidence, unless it is undertaken on an annual basis as pollards.
After a short break, Dr. Jon Heuch shared about Soils, Clay and Climate. He explored what makes up soil, what is clay, soil voids and soil water. Soil water deficit was defined.
After the lunch break, the course moved outside to explore some scenarios. The dynamics of trees and structure became apparent. In one scenario, Giles explored how the existing structure was unaffected by a nearby oak tree. A corridor within the building has been constructed and he highlighted that if this was a conservatory, there could be problems as it would be unlikely to have deeper foundations.
We then returned inside to explore a case study scenario. This was presented by Bob. It was based on a property which dated in part to the 1700s, on a silty soil. The issue of tree safety was explored, as we, as professionals, have a duty of care to highlight unsafe trees we find on a site. The group first considered courses of action if the trees were on a clay soil, and then on the actual silty soil.
Finally, Dealga concluded the day by exploring the new report template, what should be included, the need for consistency, relevant disclaimers and insurance. He also emphasised the importance of professional development, which is increasingly required for the professional.
The course was very well received, and I look forward to the new date when Giles and Bob will be delivering.
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