Cliveden Conservation’s Stonemason, Amelia Morrison, discusses the sensitive conservation of ruins and the various challenges it presents, from the removal of vegetation and cementitious hard capping to the application of lime mortar in all weather.
Sensitive conservation is crucial to preserve the complex structure of ruins. There is a considerable amount of subtlety when it comes to specifying, and a reactive approach is necessary to protect the remains. When working with ruins, it must be accepted that permanent solutions are not necessarily realistic; our aim is not to freeze the structure in its current state but to slow the decline as much as possible using an approach that can be distilled into three priorities: evaluate the effects of historical interventions and remove only what is essential for the preservation of the site, wherever possible, retain all features of historic significance, however small or seemingly insignificant, and only add that material which is necessary to slow the decline of the ruin.
Cementitious hard capping can be problematic
The use of cementitious hard capping is often the most common and damaging of all historic interventions. Moisture can be trapped behind it, causing the historic mortars and stone to decay more rapidly, and cracks and fissures on the surface can allow vegetation to take hold. Cementitious hard capping can also overburden the lower portions of the walls.
Although removing cementitious hard capping may seem like the best solution, the conservation team must consider whether it is causing further damage and the impact of removing it. For example, will it cause additional damage and losses? At Ankerwycke Priory, a 12th-century chalk rubble ruin near Runnymede, it was necessary to remove approximately 500mm of material across the entire wall head; the weight of the cementitious hard capping was crippling the lower sections of wall, allowing vegetation to take hold where it was failing, and creating a differential erosion zone where it met the historic mortars below. Cementitious repointing was also causing significant recession to the chalk faces.
In contrast, King John’s Castle in Odiham (built c.1207) is comparatively stable despite the presence of cementitious mortars right across the higher elevations. This may partly be due to the high proportion of flint in the rubble walls, which is far more robust and can stand up against harder mortars more readily than softer stones. It would be detrimental to remove cementitious mortar which is not failing, and on such a vast scale that it would seriously alter the profile of the ruin.
Tackling the growing roots of vegetation
Removal of vegetation is another common theme of ruin conservation, particularly the challenge of removing and discouraging invasive and woody species such as ivy, buddleia, and valerian. These can make their way onto ruined structures via natural means but also by design. Planting ivy was popular during the 19th century and was frequently introduced and cultivated to enhance the aesthetics of ruins. It is a particularly pernicious plant; the roots can easily tunnel through a rubble core, ripping the structure apart, and are almost impossible to eradicate manually without completely dismantling the ruin. Previously, the reliance has been on herbicides, but with the ever-growing restrictions on their use, not to mention the adverse effects they are known to have on the environment, it is necessary to find innovative approaches to the issue of invasive vegetation. Currently, the most sustainable solution is regular maintenance so vegetation can be removed or suppressed before it becomes unmanageable. This approach, once established, also causes minimum disruption to wildlife living in the area.
Preserving historic features is paramount
On each project, it is vital to identify historic features and make every effort to preserve them. Even a single piece of original ashlar, still in situ, offers insight into historic building techniques and helps visually interpret historic sites. At King John’s Castle, lower sections of the surviving medieval chimney flue were in danger of collapse. Cliveden Conservation’s stonemasons carefully recorded, dismantled, and re-bedded each stone with the incorporation of basalt bar supports. This allowed for the historically significant feature to be saved without compromising the aesthetics.
When specifying mortars to consolidate what remains of a ruin, aesthetic considerations must be balanced with performance; the mortar must be robust enough to withstand a battering from the elements – something mortars found in a rubble core would not have been required to do – whilst retaining permeability, and the appearance of the original mortars, taking into account visual differences between building phases and day-breaks.
The effective use of soft capping
On various projects, we are now getting the opportunity to not only install new turf soft capping but also inspect and maintain established soft capping. Soft capping was installed at Reading Abbey Ruins five years ago and regular inspections have shown a good result. The wall heads are weathering well, and the introduced drought-resistant sedum is thriving and appears to be suppressing the growth of undesirable, woody species. It will be interesting to monitor progress over the coming years, but for now it is offering an ecologically sound, low-maintenance solution to protecting wall heads.
Continual monitoring and maintenance are essential
Conservation cannot stop once a project or phase of work is complete. Regular maintenance and management are vital to the longevity of our ruined structures. This can be delivered by rolling programmes where professionals can undertake work with a ‘little-and-often’ approach, allowing for areas of concern to be properly monitored and action taken to nip problems in the bud. It is also beneficial to empower those involved with the site on a day-to-day basis to conduct a limited number of tasks under appropriate supervision. Volunteer teams and Friends Associations are typically the people best placed to notice any changes in the structures and report concerns. We have built a strong working relationship with the gardening team at Reading Abbey Ruins, issuing advice on vegetation removal and checking in regularly on the condition of the ruins. We have also provided basic training sessions to National Trust volunteers and Rangers at Ankerwycke Priory. This enables them to conduct limited maintenance and helps them recognise and report areas of concern.
In conclusion
Ruins across the country, particularly those that are more isolated and less visible, are susceptible to deterioration and therefore pose an imminent threat to the loss of a key element of our built heritage. Their management, care, and maintenance by experienced conservation professionals like Cliveden Conservation is essential. Regular upkeep of ruins is critical for our heritage industry and vital in training the next generation of heritage craftspeople.
For more information visit: www.clivedenconservation.com