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The Guildhall, Derry

Londonderry, Northern Ireland
Stronghold Preservation have been involved in a number of elements within this major renovation project at one of Londonderry's iconic buildings; carrying out bird guano removal, bird control & netting, waterproofing the basement, structural repairs (Cintec anchors) and timber resin splice on rotten timbers, caused by dry rot.


  • During the major restoration works, bird control, basement waterproofing, Cintec anchors for structural repair, and timber resin splice for wood decay works were carried out, Northern Ireland (NI) 
  • Wet rot was found in the timbers in the bell tower, Londonderry, Northern Ireland 
  • The wet rot was removed, and reinforcing bars were inserted to repair the structural timber & bond the new timbers to the existing at The Guildhall, Derry, NI 
  • The wet rot has been removed, and reclaimed pitch pine has been spliced and bonded onto the existing timbers, at The Guildhall, Londonderry, NI 
  • Evidence of damp and wet rot at The Guildhall, Derry, Northern Ireland: note the crumbling timbers 
  • Evidence of damp and dry rot in the trusses at The Guildhall, Londonderry, Northern Ireland 
  • The dry rot has been removed, and reclaimed pitch pine has been spliced and bonded onto the existing timbers, at The Guildhall, Derry, NI 
  • Shakes in trusses in the roof structure at The Guildhall, Londonderry, NI 
  • Shakes in trusses repaired using a resin injection method at The Guildhall, Derry, Northern Ireland 
  • The existing main council chamber, within which, Stronghold Preservation carried out remedial timber repairs for wet rot, dry rot and woodworm, at The Guildhall, Londonderry, Northern Ireland 
  • Shakes in trusses in the roof structure at The Guildhall, Londonderry, NI 
  • The existing timber panelling and trusses, which were suffering from damp, wet & dry rot, and woodworm infestation at The Guildhall, Derry, NI 
  • Detail of the existing ceiling and roof, which was treated with boron preservatives and insecticide, to eradicate wet rot, dry rot and woodworm at The Guildhall, Londonderry, NI 
  • Dry rot in timbers; red crumbly wood, at The Guildhall, Derry, Northern Ireland 
  • Bird wire on ledges to deter pigeons and birds, at The Guildhall, Londonderry, Northern Ireland 
  • Bird wire in openings to bird proof against nuisance pigeons at The Guildhall, Derry, NI 
  • During the major restoration works, bird control, basement waterproofing, Cintec anchors for structural repair, and timber resin splice for wood decay works were carried out, Northern Ireland (NI) 
  • Wet rot was found in the timbers in the bell tower, Londonderry, Northern Ireland 
  • The wet rot was removed, and reinforcing bars were inserted to repair the structural timber & bond the new timbers to the existing at The Guildhall, Derry, NI 
  • The wet rot has been removed, and reclaimed pitch pine has been spliced and bonded onto the existing timbers, at The Guildhall, Londonderry, NI 
  • Evidence of damp and wet rot at The Guildhall, Derry, Northern Ireland: note the crumbling timbers 
  • Evidence of damp and dry rot in the trusses at The Guildhall, Londonderry, Northern Ireland 
  • The dry rot has been removed, and reclaimed pitch pine has been spliced and bonded onto the existing timbers, at The Guildhall, Derry, NI 
  • Shakes in trusses in the roof structure at The Guildhall, Londonderry, NI 
  • Shakes in trusses repaired using a resin injection method at The Guildhall, Derry, Northern Ireland 
  • The existing main council chamber, within which, Stronghold Preservation carried out remedial timber repairs for wet rot, dry rot and woodworm, at The Guildhall, Londonderry, Northern Ireland 
  • The existing timber panelling and trusses, which were suffering from damp, wet & dry rot, and woodworm infestation at The Guildhall, Derry, NI 
  • Detail of the existing ceiling and roof, which was treated with boron preservatives and insecticide, to eradicate wet rot, dry rot and woodworm at The Guildhall, Londonderry, NI 
  • Dry rot in timbers; red crumbly wood, at The Guildhall, Derry, Northern Ireland 
  • Bird wire on ledges to deter pigeons and birds, at The Guildhall, Londonderry, Northern Ireland 
  • Bird wire in openings to bird proof against nuisance pigeons at The Guildhall, Derry, NI 

Further Information


Pigeon Guano Removal
 Stronghold Preservation were instructed to safely remove all the pigeon droppings from the building, prior to any other refurbishment works being carried out. Dried pigeon guano, within an enclosed space, is classified as a hazardous substance. Therefore, only trained and protected site personnel were allowed on site during the guano removal process. Personnel have to wear respirators and protective clothing, ensuring all areas of skin are covered. Initially, the droppings were sprayed with a bactericide solution to eradicate any insects, dampen the guano and reduce the dust raised. The affected areas were thoroughly brushed and cleaned. Once the area was cleaned, a final spray of bactericide was applied to sterilise the area. All droppings were double bagged inside the building, and safely disposed, so as to prevent contact with the public.

Bird Netting
To prevent re-infestation of the Guildhall, Stronghold Preservation designed and installed a bird proofing system, including a fine mesh bird netting to the open windows / louvres in the bell tower. Bird spikes were also installed to the ledges to prevent roosting on the outside of the building.

Basement Waterproofing
 The existing basement was found to be damp, with no apparent sign of any basement waterproofing system currently in place.  A cavity drain basement waterproofing membrane system was designed and installed for this building, with the membrane extending along the floor and up the retaining walls.  As the basement is a full basement, a sump and pump system was also installed.  The pumping system has a mains pump, along with a secondary, battery operated pump, incorporating an alert system for high water levels.

Wood Rot & Timber Resin Splice
 Stronghold Preservation were requested to carry out a survey to evaluate the wood rot to the timbers of the bell frame within the tower and provide timber repair solutions. It was found that there was visible wet rot decay affecting three of the timber members supporting the bell. It was recommended that the bell be propped, the rotten timber removed and the affected timbers spliced with reclaimed pitch pine, and bonded using a timber resin splice system. Whilst on site, it was discovered that there was a timber ring beam encased within the masonry bell tower; Stronghold Preservation core drilled the ring beam to assess the extent of the wet rot. It was the conservationist architects preference to retain this ring beam; therefore Stronghold Preservation suggested that the beam be injected with a boron preservative to prevent further decay of the timber, thus increasing the timbers longevity.

Structural Repairs
 The structural engineer had concerns regarding the structural stability of the decorative stone pillars on the front of the building, and requested that Stronghold Preservation install a number of Cintec socked anchors to pin the pillars back to the main building, and maintain structural stability.

 

The Guildhall is an iconic Grade A listed heritage building in Derry City, located just outside the historic walls. It was built in 1887 in the neo-gothic style. Decorated with Dumfrese sandstone, marble, oak panelling, ornate ceilings and stained glass windows, it has been refurbished a number of times over the years, and is currently undergoing another major conservation project.