Cannon Preservation – Case Studies:
This is a project involving Crack Stitch Repairs and Cavity Wall Ties renewal and isolation.Property is of around a 100 years old and built of red stock bricks and very close to the sea.
Sea salts appart from driving rain can cause alot of damage to timber and steel fixings,once the moisture enters the outer leaf it can then start causing issues to the Wall Ties and move around the cavity.
Property was Surveyed in April 2011 and found to have a large crack to gable end of around 3 metres in height and around 250mm to 500mm from corner/buttress of property.Cause was due to Cavity Wall Ties corroding and causing vertical cracking in a fork like fashion,wall ties were fishtail ties and due to the steel corrosion and rusting they expand and cause damage to surrounding brickwork.
Work started on 9-5-2011 and completed on 16-5-2011 on gable end only.
Works involved were Crack Stitch Repairs over the 3 metres in height and as per photos it involved grinding the mortar bed every four courses(13 in total) at 60mm deep and using Helical Stainless Steel Bars inbedded into a 10mm/20mm bed of resin compound and then repointed,all cracked brickwork was either replaced or repaired with a grout to a similar colour.
Cavity Wall Ties: Wall ties to gable end were found to be corroded and or rusty to about 90% and in need of replacing and isolating.All wall ties were located using a metal detector then mortar was removed around the ties by meens of a angle grinder and then all ties were isolated using a clam/sleeve to stop any more moisture to affect the steel ties and cause any more expanssion. New ties were introduced by drilling into both leaves and being the cavity was 75mm the wall ties were 220mm Helical and stainless steel.With a fixing of no less than 50mm into the inner leaf these were then resin fixed due to the soft stock and lime mortar mix for a better fixture,outer leaf was a dencer mix of sand,cement and clinker mix and also resin fixed,finishing off was repointing all area`s that were effected by cracking, new wall ties and stainless steel rods.