BS 5837:2012 What it Means
BS 5837:2012 What it Means
BS 5837 Reports and Surveys for Property Developers and Construction Sites

Briefing note on the implication of the new BS 5837 revision for planning professionals

A full revision of BS 5837: Trees in relation to design, demolition and construction, comes into effect on 30 April 2012. There are some important changes with the potential to significantly impact on planning applications and the management of sites with trees:

Expect a dramatic reduction in the area of hard surfacing allowed in root protection areas (RPAs). Clause 7.4.2.3 states: “New permanent hard surfacing should not exceed 20% of any existing unsurfaced ground within the RPA”, which is a significant move from the previous wording, which stated: “11.3.4: new impermeable surfacing within RPAs should be confined to … an area no greater than 20% of the root protection area…”. The old figure only applied to “impermeable” surfacing, whereas the new wording relates to all “permanent hard surfacing”, which appears to include permeable and impermeable. This is likely to make it much more difficult to install surfacing within RPAs unless planning submissions are accompanied by case studies supporting deviations from the BS recommendations.

Confusion over whether category C trees (low quality) are now a constraint! If local planning authorities (LPAs) strictly adhere to the letter of the new BS, we may see projects being forced to retain low quality trees. The old BS had a clear presumption that poor quality trees (called category C trees as opposed the better category A and B trees) “will usually not be retained where they would impose a significant constraint on development”, which limited the extent to which LPAs could use the existence of poor trees to obstruct development. However, the 2012 revision confuses that position, stating “…relevant constraints should be plotted around each of the category A, B and C trees…” without any qualification that category C trees should not be a material constraint. In the context that category A, B and C trees can often represent the majority of trees on the average development site, LPAs seeking to block development could insist that category A, B and C trees are retained! Other than going to appeal, the only way to counter this will be through robust and qualified expert tree support for planning submissions.

All veteran trees are now to be listed as category A (high quality), which means that there will be a presumption to retain them. Such trees usually have large trunks, which could result in a 15m radius for the biggest trees. Furthermore, it is recommended that “no construction, including the installation of new hard surfacing, occurs within the RPA”. Of course, there are often very good arguments to say that veteran trees require a smaller than normal RPA, but this is a technical issue that would have to be supported by expert analysis.

It is no longer possible to displace RPAs by 20% in any direction for open grown trees, which means the only opportunity to adjust RPAs is now through expert interpretation. This rule has been removed, which means it is no longer possible to adjust RPAs using a simplistic recipe.

Calculations of the RPA will now be more complex and require expert interpretation. The rules for measuring multiple stemmed trees have been expanded, so it is no longer a simple single measurement at ground level. This will require more measurements and a greater degree of interpretation at the time of inspection.

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