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

BS5837: 2012 Trees in relation to design, demolition and construction
AA Road show presentation notes: Richard Nicholson May-July 2012
Edited by Mike Sankus
default in BS5837: 2005 because the standard apparently said you can, but now the
message is very clear and it cannot be assumed that you can build in the RPA.
Paragraph 7.1.3 – This is very important. Notwithstanding the fact that commentary on
clause 6 and paragraph 6.1.2 (e) intimates that details of foundation design inside the RPA
might follow planning consent (at condition stage), this paragraph 7.1.3 makes clear that
technical feasibility of proposal for construction inside the RPA should be tested at planning
application stage by submitting details with the planning application for validation. It also
links to paragraph 7.7.2 and annex B (Table 1 planning applications).
For works outside the RPA see Annex B (Table1 Reserved matters/planning conditions).
Paragraph 7.2.1 - Gives useful guidance on what cannot happen inside the RPA and what
might be acceptable if it can be justified in arboricultural terms
Paragraph 7.3.1 - Relates to access facilitation pruning, but the extent must be considered
in light of paragraph 3.1 which reiterates the need to ensure pruning works do not have a
significant adverse impact of retained trees. See BS3998: 2010 and in particular text
relating to limitations of crown lifting.
Sub section 7.4 - Permanent hard surfacing within RPA
THIS SECTION DOES NOT APPLY TO VETERAN TREES
Paragraph 7.4.1 - Note relates to site-specific conditions and the expert advice of an
arboriculturist.
Paragraph 7.4.2.1 - Makes clear that design should not require excavation inside the RPA
other than for the removal of turf.
Paragraph 7.4.2.3 - The acceptability of 3m or 20% incursion into the RPA contained in
BS5837: 2005 was frequently misused or misunderstood. BS5837: 2012 limits incursion to
20% of existing UNSURFACED area. This is repeated in paragraph 7.5.3, which also points
out that it must bear on existing ground level. This applies to hard surfacing and buildings
alike, as the impact is similar.
Paragraph 7.4.2.4 – Mentions that de-icing salt needs an impermeable barrier because of
the damaging effect of de-icing salt in solution on tree roots. This issue needs to be
considered when drafting the Arboricultural Impact Assessment (see paragraph 5.4.3 h).
Paragraphs 7.4.2.5 & 7.4.2.6 - These paragraphs are all about permeable surfacing
requirements.
Paragraph 7.4.2.6 - Arboriculturists should reference Morgenroth and Buchan 'Soil moisture
and aeration beneath pervious and impervious pavements’. ISA Landscape Below Ground.
Volume III.
Paragraph 7.4.2.7 - Highlights the need to consider the performance of surface from the
point of view of future tree growth.