BS5837: 2012 Trees in relation to design, demolition - Arboricultural ...

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BS5837: 2012 Trees in relation to design, demolition and construction AA Road show presentation notes: Richard Nicholson May-July 2012 Edited by Mike Sankus Paragraph 4.4.2.9 – Provides information about shrinkable soils and hedgerows. This was added at request of engineers Paragraphs 4.5.3 & 4.5.7 - Tree categorisation no longer uses R as a tree grade and includes U instead. The reason for using U and not R is that it removes any assumption that R = Remove. Paragraph 4.5.4 - Generally the same weight is accrued for each subcategory as before (see below). The sentence "would not accrue added value" was present in BS 5837:2005, but is no longer in the text. Effectively it’s the same as it was, but the Note is in the wrong place in the process. The note in BS 5837:2005 at the end of the table: "Whilst category C trees will usually not be retained where they would impose a significant constraint on development, young trees with a stem diameter of less than 150mm should be considered for location" has been taken out of the standard and does not appear in BS5837: 2012 because Table 1 is about gathering the data in order to make decisions, not about condemning a tree before all the data has been gathered. Paragraph 4.5.7 - Upgraded means it’s a U grade tree, based on 3 bullets, but its conservation, heritage, landscape or cultural values make a case for it to be upgraded to a C grade tree for the short term. This of course is subject to the safety issues also mentioned in this paragraph. Paragraph 4.5.8 - The reference to irremediable diseases applies to serious ailments, which have a significant impact on the safety of a tree in the short term. For example Inonotus on Plane or nail galls on a Lime shouldn’t downgrade a tree which would otherwise be graded A, B or C to a U grade tree. The same logic applies to the third bullet point under U grade trees in Table 1 Table 1 - Remaining life expectancy is used in BS 5837:2012, rather than ‘substantial’ or 'significant' contribution as in set out in BS5837: 2005. Trees can contribute when they are dead. Trees graded A , B or C are largely about trees that are not dead. OED Definitions – Quality: Distinguishing characteristic, the character or nature of something. Value: Desirability in respect of some property. Paragraph 4.5.10 - Young trees were raised as being important by the review group in DPC but there was no support for this view so it was removed. Paragraph 4.5.11 – There is a definition of veteran in paragraph 3.12 which is taken from BS 3998: 2010. The importance of veteran and ancient trees is highlighted here. Both are classed as A3 grade trees because there was a feeling that an ancient, largely dead tree could, under BS5837: 2005 could too easily be classified as an R grade tree.
BS5837: 2012 Trees in relation to design, demolition and construction AA Road show presentation notes: Richard Nicholson May-July 2012 Edited by Mike Sankus Paragraph 4.6.1 – The RPA refers to Annex D, which provides the radius based on measured stem diameter @1.5m. It saves the calculation and prevents ridiculous RPA's with too many decimal places. It was requested at public consultation. The drawings at Annex C are based on those from Australian National Standard. Multi stemmed trees are based on cross sectional stem diameter not area. Paragraph 4.6.2 - The frequently misused term ‘Open grown' found in BS5837: 2005 has been removed and replaced with new wording in BS5837: 2012. Paragraph 4.6.3 - The list order has been changed and the phrase ‘when known’ has been omitted from BS5837: 2012. Section 5 - Proposals: conception and design Paragraph 5.1.2 - Project arboriculturist appears for the first time and stays until section 7 Demolition and construction in proximity to existing trees. Paragraph 5.2.2 – Refers to designs which should avoid unreasonable obstruction to light and refers to BR 209, which is frequently used by planners to assess daylight and sunlight issues. It contains a specific appendix on trees. Paragraph 5.2.3 (f) - Solar collectors are referenced. See Thayer - Solar access and the urban forest. Arboricultural Journal, 1983. Volume 7 Paragraph 5.2.4 – There is a note concerning climate change resilience and the contribution of large species. Emphasises the need to take care at conceptual and design stage for successful integration of healthy trees. Paragraph 5.3.1 – The heading ‘Proximity of structures to trees’ in BS5837: 2012 replaces 'proximity of trees to structures’ in 6.3 of BS5837: 2005. There is a new default position, which states that all structures should be sited outside the RPA of trees to be retained unless there is an overriding justification and the project arboriculturist can demonstrate that it would be acceptable to do otherwise. Paragraph 5.3.2 - The cumulative effects of incursions into RPAs was only a note at 6.2.3 of BS5837: 2005. It is now a significant consideration in BS5837: 2012. There is a new consideration regarding the acceptability of further activity within the RPA. Paragraph 5.3.4 - Shading is better defined and the mix up of sunlight and daylight has been rectified in BS5837: 2012. The benefits of shading are spelled out better than it was in BS5837: 2005. See also paragraph 5.2.2. Sub section 5.4 - Arboricultural impact assessment This is not an implications assessment (new wording). This assessment evaluates the effects of the proposed design, including potentially damaging activities such as removal of existing structures and the location and dimension of all proposed excavations or changes
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