First Derry Presbyterian Church, Londonderry

Derry, Northern Ireland
This Grade B+ historic Church, built in 1790, was severely affected by damp ingress and dry rot to the roof trusses. The main roof trusses, which span over 18m, were in very poor condition: some of the timbers were decayed by dry rot by up to 4 metres from the bearing end. Some of the support members had slipped out of position due to the movement caused by the damp. Stronghold Preservation were involved from the beginning, carrying out timber condition surveys, reports and providing remedial solutions to the Architect and Engineer.

Further Information

Truss Realignment
The dry rot and damp had caused the timber truss connection nodes to slip out of place. Stronghold Preservation assisted the main contractor during discussions about lifting the trusses off the roof, to allow the repairs to be carried out at ground level, and to allow a ring beam to be constructed to the top of the wall. The roof trusses required re-alignment and Stronghold Preservation completed this at ground level with strategically placed winches and support straps, to ensure that the truss was re-aligned without damage.

Timber Resin Splice
To satisfy the heritage funding bodies and to retain the original features of the trusses, it was decided that a bonded timber repair, using special resin adhesives, was to be used. This involved replacing decayed and rotten timbers with reclaimed timber, splicing with 25mm diameter high yield steel, bonded to the timber in slots and drilled holes concealing the bars. Over 100m of deep shakes were also cut out and replaced with moisture matched timber. Working closely with the Contractor, Architect and Engineer, Stronghold Preservation used their in-house skilled joiners, who have a wealth of experience in similar repairs to historic buildings, to complete a sympathetic and appealing aesthetic repair.

All new timbers, and any wood in 'at risk' areas were treated with a boron preservative, which gives the timbers protection from damp and wood rot.