Case 1
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
Cause of Defects
The source of moisture:
(i) from behind the paint (from the substrate beneath the paint)
(ii) on the paint arising (from condensation due to high RH in a poorly ventilated basement)
In this case, the defect may be caused due to water seepage through the external wall of the basement. The outside surface of the basement wall is often subject to moisture but is usually protected by waterproofing membrane or other means of waterproofing. However, when the waterproofing system becomes defective, moisture, entering the basement wall, will travel inward and build up capillary pressure under the paint coating. This capillary pressure is capable of pushing the paint film from the surface.
The details of the waterproofing system may be insufficient to control the water seepage when there is a leakage through the joint. This leads to the peeling off of the paint coating on the column. Other possible causes of waterproofing failure may include:
- Poor application
- Material deterioration
Poor detailing or installation of the construction joint may contribute to the lack of water-tightness at the joint. Hence, this leads to water seepage. Ground settlement could also have caused cracks which may lead to water penetration.
Basement water seepage – courtesy of DryProof
Waterstops and drainage details are common devices in controlling water seepage through construction joints in basements. Proper installation of waterproofing details at these joints to achieve optimum watertightness could be achieved by the following:
(a) Internal waterstops can be secured by using wires to hold them in place.
(b) External waterstops are tied to the formwork of concrete works.
(c) Flanges of waterstops should be tied to the reinforcement steel at an interval of 300 mm along the flanges.
(d) Bulb of the waterstop should be placed directly onto the midpoint of the joint for efficient expansion actions.
(e) Individual sections must be properly jointed by special junction pieces.
- The porosity of concrete, coupled with crack lines, allows the ingress of water, and, when re-surfaced, may result in the formation of efflorescence (deposit of salt) and/or calthemite (deposit of calcium carbonate).
- This is exacerbated by the formation of cracks due to the weak tensile strength of concrete against stresses resulting from shrinkage, differential settlements, etc.
