CPD articles

Continuing professional development: Heritage work

2 May 2018 | By Paul Wankiewicz

Hardwick Hall’s exposed position has left the stone at risk of damage from wind and rain

Construction professionals working on conservation projects face different challenges to the wider industry. CM looks at the heritage sector’s key requirements and best practice, in consultation with the National Trust’s Paul Wankiewicz.

With over six million traditional buildings and more than 500,000 buildings or structures in the UK, there is considerable demand for construction professionals who understand the nature and practicalities of conservation projects.

The work often provides unique challenges and should always demand high standards, and appreciating the significance of the building – which could be social, historical, cultural, economic or environmental – is key on any heritage project.

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As Chartered Institute of Building president Rebecca Thompson, who runs her own heritage consultancy, puts it: “Recognising the history of a building is central to a healthy working relationship with heritage clients.”

There are several recognised best practice guides for work in the heritage sector. Foremost among these are BSI’s BS 7913 standard Guide to the Conservation of Historic Buildings, the National Trust’s Conservation Principles and the International Council on Monuments and Sites (ICOMOS) charter Principles for the Analysis, Conservation and Structural Restoration of Architectural Heritage.

These principles, which incorporate such issues as taking an integrated approach, accountability and working with change, lie at the heart of how construction heritage specialists need to approach conservation projects, says National Trust senior building surveyor Paul Wankiewicz.

“Not all the principles can be adopted on every project, but they can be used to form an understanding of the significance of the building,” he says. “From there, a judgement can be made on what work needs to be done to the building.

“A considerable amount of work on any conservation project will be done in advance – using the principles to inform decision-making. In some respects, doing the work on site is the easy bit.”

The principles of ICOMOS and the National Trust are incorporated into the BS 7913 standard.

“It integrates them in one concise usable document,” says Wankiewicz. “BS 7913 could be regarded as the key document for construction professionals working on conservation projects. It should be the first point of reference for anyone starting out in conservation.”

Detail from Hardwick Hall Gatehouse renovation plan

BS 7913 is intended for owners and managers of historic buildings, for the conservation project team’s contractors and other advisers. It includes key terms and definitions, and explains heritage values and the concept of “significance” – which is central to the standard’s recommendations for conservation projects.

“Heritage has cultural, social, economic and environmental values. The attributes that combine to define the significance of a historic building can relate to its physical properties or to its context,” the standard explains.

“Significance could represent a public interest, the planning system, and the policy and legislation which support it. Research and appraisal into the heritage values and significance of the historic building should be carried out to ensure that decisions resulting in change are informed by a thorough under-standing of them.”

The document also expresses the need for conservation, repair and maintenance of historic buildings to be managed and undertaken by competent persons who will understand the nature of the materials and the skills required to use them, as these are very different to the application of modern techniques.

The key difference between traditional (pre-1919) buildings and those built after is the permeable nature of the materials used in older buildings.

“Producing the correct specification, understanding traditional building techniques and materials and communicating this via the specification and site visits is essential to achieving the correct results,” says Wankiewicz.

Conservation projects should start with an initial desktop scoping exercise, using historic environment records and other resources to identify archaeological sites, “designated heritage assets” and other available data. These can be often be found in local archives such as county records offices, or further afield in national archives such as the wealth of information on databases held by Historic England.

Hardwick Hall’s sandstone exterior requires ongoing maintenance

It is critical that the significance of a place is understood in order to mitigate the risk of losing or compromising components of the site which have values – whatever these might be. Heritage impact assessments (HIAs) should also be used to understand the effect of development and changes on the historic asset, and how the impact of change might be mitigated.

Condition surveys and inspections should involve reference to a site plan to reference locations, areas and components, as the BSI standard explains, and they may include photographs and drawings. The process involves inspection with recording of a narrative, sometimes with detailed analysis and identification of defects.

Surveys and inspections can conclude with the need for more detailed assessment, focusing on areas such as architectural paint and plaster analysis, timber decay assessment, structural movement monitoring and environmental monitoring for dampness and humidity.

Asset management plans are employed by many larger historic buildings, which undertake planned surveys and inspections. An example is Hardwick Hall in Derbyshire (see box, p37). The BSI standard recommended best practice is for planned surveys every four or five years, a system which is adopted by most larger conservation organisations such as the National Trust and English Heritage.

Significance should inform the framework used for managing buildings and as part of operational care and other interventions – the methodology should be proportionate to the nature and history of the building, its ownership, use, need for repairs and any proposed works.

A section in BS 7913 is devoted to advice on the creation of strategic plans and conservation management plans in particular, which includes guidance on stakeholder involvement, the positions aimed for at the end of the plan period, resources and materials, and key performance indicators to measure the effectiveness of plans.

CIOB Academy conservation course

The CIOB Academy has developed its own heritage course for construction professionals, covering conservation for residential and commercial property, plus historic monuments.

The two-day course, Understanding Building Conservation, follows the ICOMOS training and education guidelines and BS 7913.

It introduces the philosophy behind conservation before going into detail regarding the technical analysis of buildings, ensembles and sites, diagnosing issues, identifying the best building conservation solutions, working with the stakeholders, and ultimately providing advice regarding best practice.

Those who pass the course will be eligible for further recognition through the new CIOB Building Conservation Certification Scheme.

The course is open to any construction professionals who work with traditional buildings. It is intended as an ideal grounding for anyone new to conservation work.

For further details see www.ciobacademy.org

The standard stresses that understanding is key prior to any alteration to the building fabric. It follows a principle of “minimum intervention” set out back in 1877 in the manifesto of the Society for the Protection of Ancient Buildings.

In line with this ethos, it advises: “The level of intervention should be the minimum necessary to stabilise and conserve the historic building, ensure its long-term survival and meet the requirements of any foreseeable new use.”

In some instances, it may be desirable to “consolidate” a building in its present condition rather than “restore” it completely, as this could involve a considerable degree of conjecture. An example of this is the Gothic Ruin on Belton Estate in Lincolnshire (see below), where it was decided that a full restoration would have altered its character in the context of its setting.

“The building was constructed to represent a ruin and the purpose of the works was to stabilise the structure,” says Wankiewicz.

The principal objective of any repair work on a conservation project is to retain the performance of the existing fabric, best achieved by matching materials and using traditional repair techniques. There are instances where modern methods might be appropriate – the use of synthetic resins for timber repairs is cited by the BSI standard – but they need to be thoroughly researched before they are specified, as irreversible damage can be caused.

Alterations should be carried out only if there is no suitable alternative, and should be designed to minimise their impact on the significance of the historic building, and avoid losing features that contribute to that significance. New insertions – such as sub-dividing walls – should be contoured around original features and mouldings so they can be removed in the future, leaving the original fabric intact.

In the case of materials, BS 7913 states: “Where possible, existing materials should be investigated and tested so that good performance and aesthetic matches can be achieved. In cases where the existing material source is not available, re-use of suitable materials from salvage might give better results than newly formed materials.”

“BS 7913 could be regarded as the key document for construction professionals working on conservation projects. It should be the first point of reference for anyone starting out.”

Paul Wankiewicz, National Trust

Water and moisture ingress is a common problem in historic buildings and should be thoroughly investigated to establish the cause so that the appropriate solution can be identified. The root cause of the ingress should be prevented or diverted prior to repair – this could take the form of a defective gutter, for example.

Other common problems found in historic buildings include fungal or insect attack and metal corrosion. “These may require specialist targeted investigations,” says Wankiewicz.

The emerging field of “building pathology” has a broader focus than the decay of materials, and encompasses the way components interact and how spaces are used. It can be useful in understanding ventilation in historic buildings, where chimney flues, sub-floor vents and cupolas contribute to a passively managed environment.

Project management and supervision is a key element in any conservation work, as there is a far higher risk of defective work where there is no robust project supervision from a competent person. BS 7913 states that:

“A contractor’s site or works supervisor should be responsible for ensuring specifications are compiled in accordance with the required quality standards. The contractor should prepare a project execution plan that describes how this is to be achieved and how this is to be inspected and tested.

“This form of quality management should be based upon risk assessment of specification non-compliance. Inspection and supervision should be carried out at appropriate stages, for example during the repointing of masonry.”

Project records, including as-built drawings, descriptions and photographs, should also be kept for all conservation work, as they form a record for the works. “They should also record the decision-making process,” says Wankiewicz.

BS 7913 also includes a section on maintenance. Although this is the responsibility of historic building owners and managers, the standard describes maintenance as “the most common and important activity in conservation and preservation” – yet it is frequently neglected, causing costly repairs down the line. 

“This could be described as the ‘little and often approach’,” says Wankiewicz.

Hardwick Hall Gatehouse, Derbyshire

Restoration of the gatehouse tackled the damage done by over 400 years of weathering

Hardwick Hall in Derbyshire, built in the 1590s, requires ongoing maintenance and restoration work. An example of the Elizabethan Prodigy House style, the hall is situated on an exposed escarpment, and the wind and rain have taken their toll on the building and other structures on site.

The repair challenges led the owner, the National Trust, to put a 10-year maintenance plan into place.

“The Hardwick stone is coal measure sandstone, which is soft and therefore easily worked, but this means it has a short lifespan,” explains Paul Wankiewicz, who worked as a project manager and building surveyor at Hardwick. “The problem is exacerbated as the remaining stone in the quarry is of poor quality.”

Masons have been continuously carrying out maintenance work on the hall and gardens over its history. Wankiewicz describes the cyclical work programme as “a necessary way of life” and commissioned the 10-year plan which the property currently uses to help programme and budget for repairs.

“As the works were classed as repairs, listed building consent was not required. Even so, the documents and drawings were logged with the local authority as a record of the repairs.”

Paul Wankiewicz, National Trust

“The repair philosophy is only to replace stone that is no longer structurally sound or will last less than 30 years,” he explains. “At high level, mortar repairs only take place if they will last for 30 years or more. A less rigid approach is considered justifiable at low level where access is easier and less costly.”

Hardwick’s gatehouse, which uses the same stone as the hall, was identified as requiring urgent repairs, structural work and conservation.

“A range of stonework repairs was needed, including repointing of open and vulnerable joints, descaling stonework, pinning, shelter pointing, replacement of ashlar, structural repairs and providing lateral restrain to the building,” Wankiewicz explains.

“We also wanted to look at the gatehouse’s structural stability, where the lateral restraint has been compromised by movement and shrinkage of principal roof timbers, and the stability of the stone cresting.”

Wankiewicz engaged a conservation specialist structural engineer and surveyed the proposed repairs with the Hall’s master mason, Trevor Hardy, who has over 35 years of experience on the site.

“Once we were confident our repair philosophy was in accordance with the ‘Hardwick Hall Statement of Significance and Spirit of Place’, an outline specification was prepared,” he explains.

“As the works were classed as repairs, listed building consent was not required. Even so, the documents and drawings were logged with the local authority as a record of the repairs.”

The gatehouse work included installation of a scaffold and temporary roof. “This gave better access to the structure and the repairs were reassessed,” Wankiewicz says. “The structural engineer recommended the principal beams of the gatehouse’s flat roof structure should be tied back to the stone.

“We had observed movement from ground level, but this turned out to be old non-progressive movement,” he continues. “We therefore decided not to provide the lateral restraint, as this would have required significant intervention in the building fabric. Instead, we opted to regularly monitor the area for any movement, and this monitoring has been included in the property’s cyclical maintenance plan.”

The Hall repairs project was completed, following the agreed philosophy of work at Hardwick, and all repairs were recorded and will act as the base line for future surveys and monitoring.

“The building will now fall back in to the cyclical maintenance regime at Hardwick,” says Wankiewicz.

Gothic Ruin, Belton Estate, Lincolnshire

An 18th century stone folly on an artificial island proved a challenging consolidation project.

The Gothic Ruin in the garden of Belton House in Lincolnshire is a Grade II-listed structure, and was recently subject of a heritage project carried out by the property’s owner, the National Trust.

“It is an early example of the fashionable 18th century ‘Gothic’ style and appears to have been built around 1742 by the Viscount Tyrconnel,” explains Paul Wankiewicz, who worked as a building surveyor on the project.

The ruin is located on an artificial island and stands either side of a cascade. The walls are constructed from local Ancaster stone combined with narrow bands of coursed rubble walling, all bedded in a lime mortar.

“The structure needed to be consolidated, rather than fully restored, and still give the impression of being a ruin – which is a delicate balance,” explains Wankiewicz. “A full restoration of the ruin would have altered its character in the context of its setting.”

An archaeological historic building survey was commissioned to understand the structure and its significance. This involved a full measured survey of the buildings, including plans, elevations – using a laser scanner – and a photographic survey.

“A structural engineer’s report on the structure recommended underpinning, replacing missing stones, providing a protective lime mortar cap, isolating stone replacement and removal of any organic growth,” says Wankiewicz.

Pre-planning application advice was sought from the conservation officer for local authority South Kesteven District Council, and listed building consent was required owing to the proposed underpinning.

Ahead of the tender, Wankiewicz produced a health and safety plan which identified that scaffolding over the River Witham and around the Gothic Ruin would be required for access.

“There was no easy access to the site, and as the park was open to the public and Grade I-listed, this made the works challenging from a safety viewpoint,” says Wankiewicz.

“After consulting with the property to understand their business operations, we decided to limit the size of the site compound and store materials off site. This would increase the programme for the works but would reduce the impact on the park.”

Before work started on the masonry, ivy which covered the structure was cut back and allowed to die, following consultation with the National Trust’s ecologist.

“The weight of the ivy and its roots had loosened the stones in places and made some of the larger stones unstable,” says Wankiewicz. “The wall was close to partial collapse, with a substantial lean. Movement cracks were evident.”

The masonry works involved minimal intervention, in line with the “consolidation” approach of the project. “The weathered mortar caps have been kept to a low profile but are sufficient to discharge the water from the structure,” he explains.

“Mortar samples were provided and agreed in advance of the works. Replacement stone was selected and dressed, with the pointing set well back from the stone but with enough weathering not to trap water.”

Ahead of the proposed underpinning works, trial holes were dug by the estate masons. “Unexpectedly, these exposed large existing foundations,” states Wankiewicz. “This information was communicated to the structural engineer who decided that underpinning was unnecessary.”

The Gothic Ruin is one of several structures in the gardens of Belton House which are in a state of disrepair – including fallen decorative arches and blocked waterways. Wankiewicz hopes to secure funding for surveys and subsequent repair work to consolidate these structures, following a similar approach to that taken with the Gothic Ruin.

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Robert Tiffin, 23 September 2019

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