Action Wall Ties - Specialists in masonry repair and reinforcement
tel: 01227 721255
wall tie treatment & cavity cleaning
The subject building was a conventional 1950s cavity-built semi-detached house.
Problem
• An AWT investigation with a metal detector and an endoscope revealed that the wall ties to the front, right side and rear elevations were galvanised mild steel vertical twist ties, all in a similar heavily corroded condition, showing signs of de-laminating.
• Side gable wall: This had a significant bulge at first floor level from the front to the window. This area required the external skin to be carefully dismantled and rebuilt. Corroding wall ties were clearly visible. The internal walls at ground floor level were also found to be damp.
Corrosion of the embedded mild steel wall ties had resulted in the forming of ferrous oxide, which had expanded the metal many times its original thickness, lifting and cracking the brickwork. It was considered likely that the lateral movement noted was due to the absence of effective wall ties.
• Bridging of cavities at DPC: Our investigation revealed that the building had areas within the cavity that were blocked with decayed mortar that bridged the DPC.
• An AWT investigation with a metal detector and an endoscope revealed that the wall ties to the front, right side and rear elevations were galvanised mild steel vertical twist ties, all in a similar heavily corroded condition, showing signs of de-laminating.
• Side gable wall: This had a significant bulge at first floor level from the front to the window. This area required the external skin to be carefully dismantled and rebuilt. Corroding wall ties were clearly visible. The internal walls at ground floor level were also found to be damp.
Corrosion of the embedded mild steel wall ties had resulted in the forming of ferrous oxide, which had expanded the metal many times its original thickness, lifting and cracking the brickwork. It was considered likely that the lateral movement noted was due to the absence of effective wall ties.
• Bridging of cavities at DPC: Our investigation revealed that the building had areas within the cavity that were blocked with decayed mortar that bridged the DPC.
Discussion
• Wall ties: AWT opinion, based on the Building Research Establishment’s recommendations, was that the symptoms / defects noted were consistent on all elevations requiring remedial work. It was considered that the building would benefit from remedial wall tie replacement and the isolation of the existing ties.
• Bridging of cavities at DPC: The bridging of the DPC had rendered it ineffective and could result in rising damp.
Solution
• AWT completed a remedial scheme providing a viable repair by introducing remedial wall ties, isolating the existing ties and cavity cleaning.
• Wall tie treatment: AWT operatives completed remedial wall tie treatments to the front, right side and rear elevations in accordance with AWT’s Wall tie treatment – Generic repair.
• Cavity cleaning: We cleaned the cavities to the ground floor DPC at the front, right side and rear elevations in accordance with our specifications and AWT’s methods. This meant the removal of sufficient external brickwork to enable the removal of discarded mortar debris, leaving the cavity clear to below the DPC while at all times maintaining the integrity of the wall.
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