Is Ivy Good or Bad for Historic Walls?

Ivy is often blamed for damaging masonry walls and seen as something that should be removed wherever possible. However, under some circumstances the positive benefits of ivy can outweigh any deteriorative effects. This paper reports on findings from a three-year research project, commissioned by English Heritage, and their implications for managing ivy on historic masonry walls. From field monitoring at a range of sites in England, it was found that ivy provides a thermal blanket for walls, protecting them from extremes of heat and cold and fluctuations in relative humidity. Similarly, studies in and around Oxford show that ivy can minimize particulate pollution reaching walls. Field experiments in Oxford also reveal that ivy rootlets adhering to stone generally only create minor (if any) damage to the stone surface. However, it was also found that ivy can penetrate existing voids and cause damage. A balanced appraisal should inform decisions to remove, leave or even plant ivy. If ivy is allowed to grow on walls, regular and careful maintenance and monitoring are essential.

Figure 1 Two of the study sites showing the location of iButtons to record temperature and relative humidity hourly beneath the ivy canopy and on an exposed portion of the wall adjacent to the ivy a) Worcester College, Oxford, b) Drop Redoubt, Dover.

Figure 2 Maximum and minimum daily temperatures (averaged over one year from May 2008 to April 2009) on ivy-covered and adjacent bare wall surfaces at five sites across England.

Heather Viles, MA (Camb.), MA, D.Phil. (Oxf.), Professor of Biogeomorphology and Heritage Conservation, University of Oxford

Heather Viles runs the Oxford Rock Breakdown Research Laboratory (OxRBL) and researches the deterioration and conservation of building stones, with a special interest in the role of biological influences. Her research has so far resulted in over 115 scientific papers and 14 books and edited volumes. She sat on the steering committee of the UK National Heritage Science Strategy, and is on the advisory panel of the AHRC/EPSRC Research Programme on Science and Heritage.

Troy Sternberg, D.Phil. (Oxf.), School of Geography and the Environment, University of Oxford

Troy Sternberg was the Post-Doctoral Research Assistant working on the Ivy on Walls research project and is now a British Academy Research Fellow at the University of Oxford. As a geographer his research is focused in England and East Asia where he recently worked with the United Nations on reducing environmental and social vulnerability to changing climates across the steppe grasslands.

Alan Cathersides M.Sc., B.Sc., Dip.Hort.(Kew), M.I.Hort., Senior Landscape Manager, Gardens & Landscape Team ,English Heritage

Alan Cathersides specialises in the management of historic landscapes and the landscape and ecology around historic structures. He is particularly interested in methods of management which benefit both historic and natural heritage. He has supported and been involved with recent English Heritage research projects on Soft Wall Capping and Ivy on Walls since their inception.

More information on the Journal of Architectural Conservation.

How to subscribe.

Donhead Publishing 2012