UKTC Archive

Re: Diameter callipers

Subject: Re: Diameter callipers
From: Bill Kowalczyk
Date: Aug 15 2019 12:49:10
Hi Wayne,

The oft quoted British Standard; "BS5837:2012 - Trees in relation to design, 
demolition and construction” came up with a calculation for recommended root 
protection areas (RPA), which works out at a radius of 12 x stem diameter 
(but measured at 1.5m for some peculiar reason) for most single stemmed trees.

In practice, with most trees, this invariably comes to about the same as 
measuring to the “drip-line” of the canopy edge, and accepts that roots 
beyond this zone may get trammelled without significant negative impacts on 
the health and vitality of retained trees.

It’s a bit “rule of thumb” developed by the working group who first came up 
with the standard back in the early 1990’s, but it’s all we’ve got and better 
than nothing.



On 14 Aug 2019, at 23:55, Wayne Tyson <> wrote:

What does dbh have to do with RPA? What are the standards and upon what
data doth they rest? Protection from what, for example? That is, in the
simplest terms, other than dbh how are RPA's determined?

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