Wall Tie Replacement

Cavity walls have been popular in construction for over 100 years, and help to improve thermal insulation and prevent moisture penetration. Steel ties have traditionally been used to bind the inner and outer walls together across the cavity. However, steel rusts, and as it rusts it expands. This causes cracking within the mortar joint which effectively detaches the outer skin from the inner, and can lead to collapse. Over recent years, it has become apparent that a high number of properties built before 1981 are suffering from wall tie corrosion.

Visual evidence of corrosion can be seen by horizontal and diagonal stepped cracking to external wall surfaces. If corrosion is severe it will lead to distortion and bulging and in some cases external walls have collapsed during storms. This represents a major risk to the public. Particularly around windows and doors, many properties have an inadequate number of wall ties, making these areas particularly susceptible to cracking and failure.

Latest research by the Building Research Establishment, has found that wall ties corrode faster in the mortar joints of brickwork, leading to oxidisation, where they will expand to several times their original size. This expansion will cause structural instability by lifting the mortar joints where they lay.

City Structural can carry out a wall tie survey using a metal detector to locate existing wall ties, and by inserting an endoscope through a small hole drilled into the mortar joint, to inspect their condition.