Coxton Tower is a Category A Listed building and Scheduled Ancient Monument located near Lhanbryde in Moray. It is a fortified Tower House dating from the early 17th century; an armorial panel above the entrance records the completion date as 1644. The form reflects the defensive function; the ground floor walls are 4½ feet thick and raise 4 storeys, with each storey containing a single room; the first floor entrance is reached by a later forestair and a defensive iron yett gate. The building is constructed of harled rubble masonry with ashlar dressings and margins throughout. Other key features include: round corbelled bartizans with crenellated base and wallhead, chamfered margins, iron window grills and the flush stone slab roof mounted on stone vault.
Scope of Work
Pictured: Phase 1: Coxton Tower: before works
LTM were contracted by the owners to undertake selected conservation and repair of the historic fabric. The works were divided into two phases:
Phase 1: Roof works: relaying of existing stone slabs; indenting eroded stone flags; replacement of chimney copes with vented capping; re-pointing to eaves level finished flush with slabs to allow maximum rainwater run off.
Phase 2: Conservation and repair: harl consolidation (grouting) and limewashing; conservation works to historic stonework and fabric, including restoration of original oak windows and doors using handmade nails; retention of original glass and replacement Victorian sheet glass; protection of all timberwork with a traditional linseed based paint system.
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Challenges and Considerations
Pictured: Phase 1: During works: careful removal and recording of roof slabs.
Phase 1: LTM were contracted to repair the stone slab roof. The key challenge was to record each individual stone ridge and flagstone, numbered accordingly, in order to re-lay the entire roof as accurately as possible. This required a full photographic record and systematic uplifting and mapping of each stone, course by course; the stones were then cleaned and stacked in sequence.
Phase 2: The restricted access and sensitivity of the site complex was a primary concern. LTM ensured the grounds were reinstated to their original condition after the completion of the conservation works. The works themselves provided LTM with an interesting challenge - to consolidate the original, historic harling mortar and then blend the new harl with the original in terms of texture and colour. Sections of the extant harl was ‘boss’, coming away from the masonry substrate, but the mortar itself was also delaminating between different coats or applications of successive harling. LTM masons had to carefully insert the consolidating grout via syringe to the correct depth, making sure the grout consolidated the correct layer.
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Solutions to Problems
Pictured: Phase 2: Coxton Tower: after works detail.
Phase 1: The barrel vault roof was built in rubble masonry and lime mortar, capped with flagstone. However, the lime binder had washed out over time, leaving the flagstones resting on a friable aggregate substrate with a high soil content. LTM masons removed all loose material to reach a firm base, extracting vegetation by selective dismantling and deep root treatment. The sub-base was then primed with a gauged hot lime mortar prior to rebuilding the roof slabs. The use of compatible, matching lime mortars eliminated the use of water barriers and ensured best conservation practice.
Phase 2: The original harl was retained wherever possible. The grout had to be made extremely viscous to penetrate the crystalline structure; stone dust was used as an aggregate to reduce the shrinkage and casein was mixed through to aid strength and workability. LTM masons replaced selective areas following careful inspection and removal of damaged sections back to a sound substrate. All lime mortars were analysed to replicate the existing and selected to maximise performance; the final coat was hand cast to match the original texture.
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