Cause?
The defects could be due to aging; structural movements; defective workmanship during installation; thermal movement; defective or missing expansion joints; damage caused by external factors (e.g. falling objects during typhoon); ingress of water into the gap between the finishes or tiles and the structure, etc.
How to handle?
As regards repairing of damaged external wall or finishes, all loose parts should first be removed to eliminate the imminent danger and be replaced to maintain protection to external walls. A proper key between the existing concrete wall and the newly finished layer as well as the bonding of individual tile to its bedding mortar is crucial to avoid recurrence of the same defects. Proper preparation of the exposed surfaces of the existing wall for a physical key with the new mortar; use of suitable bonding agents or adhesives for the mortar; and special adhesives for the tiles are essential means for this purpose.
Cracks should be repaired by injection of specially designed chemicals or through open-up and repair by mortar.
Legislation?
Buildings Ordinance (Chapter 123) - Buildings Department (BD)
- Investigation Order (Section 26A)
It is served upon building owners or OC where early signs of building defects are detected and requires detailed investigation to identify the extent and the nature of the dilapidation/defects. Owners/OC are required to engage an Authorized Person (AP) to carry out the investigation and to submit the remedial proposal to the BD for acceptance.
- Repair Order (Section 26)
It requires building owners or OC of buildings which are found to bear serious defects likely to cause risk of injury or damage, to carry out the required repair works and to render the buildings safe. Owners may be required to engage an AP to supervise the remedial works to the satisfaction of the BD.
- MBIS Notices (Section 30B) (Mandatory Building Inspection Scheme)
It requires building owners or OC of buildings aged 30 years or above (except domestic buildings not exceeding 3 storeys) to appoint an Registered Inspector (RI) to carry out the prescribed inspection and supervise the prescribed repair works found necessary of the common parts, external walls and projections or signboards of the buildings.
