Granite repointing and cleaning:

Greyfriars Church

Aberdeen · 2021

Our role: Masonry restoration contractor and principal contractor
Client: G1 Group PLC
Architect and contract administrator: LAS Architecture Ltd
Principal designer and quantity surveyor: McLeod + Aitken
Value: Under £0.5m
Programme: December 2019 to July 2021
Scope: Scaffold coordination, hand picking out of cement pointing, repointing in lime mortar, steam and low-pressure TORC cleaning of granite, masonry repairs, sample areas

Greyfriars Church stands on Queen Street in the centre of Aberdeen, a Gothic granite building with a tower, turrets, pinnacles and richly detailed tracery. G1 Group PLC appointed us in November 2019, under a contract administered by McLeod + Aitken to LAS Architecture's specification, to restore the external masonry: picking out and repointing the joints and cleaning the granite elevations.

Greyfriars Church, Queen Street, Aberdeen — photograph 1

Greyfriars Church, Queen Street, Aberdeen — photograph 2

Greyfriars Church, Queen Street, Aberdeen — photograph 3

Greyfriars Church, Queen Street, Aberdeen — photograph 4

Greyfriars Church, Queen Street, Aberdeen — photograph 5

Greyfriars Church, Queen Street, Aberdeen — photograph 6

The challenge

Granite is hard and unforgiving, and years of cement pointing had hardened the joints and pushed water into the stone behind. The building is also complex: tall elevations, parapets, dormers, pinnacles, tower tracery and decorative figures all needed to be reached and assessed for soundness before any repair began. Cleaning had to remove organic growth, pigeon guano and soiling without harming the granite surface, and the slurry and spray had to be kept away from the public footpath and neighbouring buildings on a busy city centre street.

Our solution

Specialist scaffold was designed and erected in lifts around the building, with a protected route for access, and we coordinated this with the scaffolder and Aberdeen City Council. Before work started we examined the stonework to parapets, dormers, pinnacles, turrets and tracery for structural competence and cut out twelve sample areas for the masonry consultant to select and approve. Cement pointing was then picked out by hand with chisels and hammers to a sound depth, joints were washed, and the beds were repointed in lime mortar, keeping the host stone damp and protecting the finished pointing with hessian. Cleaning followed the stone cleaning specification prepared by LAS and UK Stone Doctor: guano and debris were first removed from ledges, then organic growth was steamed off and the granite was cleaned with a low-pressure wet slurry using the TORC system, working from top to bottom with boarded lifts, tanking to the low-level scaffold and sheeted scaffolds to contain run-off. Windows and rainwater goods were protected, and gutters kept clear. Masonry repairs and tracery works were carried out as the inspections required.