Wall Tie Surveys
Most properties, and almost certainly those built in or after 1920s will have cavity external walls with an outer skin of 100mm brickwork, a 50mm cavity and an inner skin of either 100mm brickwork or blockwork. The outer and inner skins of brickwork/blockwork are tied together with wall ties. In older properties the wall ties are likely to be mild steel fishtail type with either a galvanised or black bitumen finish. In later years galvanised wire butterfly type wall ties were used and for the last 20/25 years, stainless steel ties.
If corrosion occurs in mild steel ties, this can cause corrosive expansion and horizontal cracking in the mortar joints can occur along the line of the ties usually located every approx. 8 courses of brickwork in older buildings and since circa 1960, every 6 courses. If wire butterfly ties corrode they usually break such that the outer and inner skins are no longer tied together causing the brickwork to possibly bow through wind suction on the face of the external walls of the property.
When carrying out site surveys Surveyors look for possible movement or damage to the brickwork which may or may not be related to wall tie failure. Surveyors may however request a wall tie survey even though there is no visible damage to the brickwork, as a precaution due to the age of the property.
In carrying out a wall tie survey we detect the wall ties on each elevation of the property using a metal detector, then drill a small hole under usually 2/3 ties on each elevation and inspect the condition of the wall ties with an Endoscope. In some cases it may necessary remove a brick or expose the end of the wall tie in the mortar joint.
The report is then submitted to the surveyor and/or mortgage lender and any decision to carry out remedial works is at the discrection of the Surveyor and/or Mortgage Lender.