Results of a BS5837:2005 – Trees in relation to design, demolition and construction Survey for an intended development of a bungalow. Although the root system (according to the calculations of the BS5837 ; 2005) would not be impeded with the structure, the garden area would be within the Root Protection Area (RPA/CEZ) and the tree was multi-stemmed with compression unions at the base. Although these unions are common on this species of Oak, a reduction of such quantity was required to allow the tree to readjust to the slight change in soil structure from pedestrian use and minimise the leverage (potential failure) of long multi-stems over a soon to be domesticated area. The Holm Oak (Quercus ilex) was reduced to an inner canopy position that you can see in the first photo. Reduction was carried out 2010.