Drum Castle, Old Tower, Drum | Restoration Case Study

Our role: Lime specialist to the design team
Client: National Trust for Scotland (via McCall Surveying)
Scope: Mortar repair specification, evaluation of repair options, input to design process

LTM Consultancy was appointed as lime specialist by McCall Surveying, on behalf of the National Trust for Scotland, as part of the design team for the repair of the Old Tower at Drum Castle.

The challenge

The tower has suffered for decades from inappropriate repairs and material choices, having been extensively repointed in cement in the mid 1980s. Water getting into the wall and generally high moisture levels in the fabric are causing significant problems for the Trust’s collections held inside. Proposals were being developed to repair the masonry as a whole.

Our solution

Our focus was the technical side of the masonry repair and the development of appropriate repair specifications for the mortars. We also contributed to the wider design process, evaluating the options and weighing the historical, aesthetic, philosophical and technical arguments on the most appropriate way forward. Our investigation of the external finishes identified three distinct phases of harling on the tower: localised remnants of a thin uncoloured lime and sand harl with a peach coloured limewash finish, substantial remnants of an uncoloured lime and sand harl with no visible limewash, and substantial remnants of a pink coloured lime and sand harl, possibly a sneck harl, with no visible limewash.

Outcomes

Right materials for the tower

Specifications for lime mortars were developed to replace the harm caused by earlier cement repointing.

Informed design decisions

The design team had the technical, historical and aesthetic arguments set out for each option.

Protection for the collection

The proposals aim to tackle the water ingress and high moisture levels affecting the Trust’s collections.

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Drum Castle, Old Tower