Heed tell-tale signs of wall cracks

A concrete sunshade dislodged at Block 201E, Tampines Street 23, on Sept 25. The writer said town councils must adopt preventive maintenance and check external walls regularly so cracks can be repaired before they worsen.
A concrete sunshade dislodged at Block 201E, Tampines Street 23, on Sept 25. The writer said town councils must adopt preventive maintenance and check external walls regularly so cracks can be repaired before they worsen.ST FILE PHOTO

Short of an earthquake, wall plasterings and well-designed concrete structures are highly unlikely to fall without first showing tell-tale signs ("Plaster falls 12 storeys from HDB blocks in Hougang"; ST Online, Nov 28 and "Sunshade dislodged at Tampines block had no rebars"; Dec 5).

Small plaster cracks must be repaired before they widen. When exposed to the elements, the concrete structure beneath may deteriorate.

If the cracks are not repaired, the reinforcement bars (rebars) embedded in the concrete structure will corrode and expand due to exposure to air and moisture.

Further neglect will lead to the concrete structure hollowing out and falling.

However, it is not easy for town council staff to check the external walls of HDB blocks because of the great height.

Even during cyclical repairs and washing and repainting of the external walls, the workers engaged by the town council's contractor may not, on their own, specifically look out for and report such cracks for timely repairs to be carried out. This must change.

Two years ago, I reported cracks about 2mm wide in the bin chute wall outside my kitchen window to the town council.

During the repair work, the contractor's workmen did a cosmetic job by painting over the cracks. They did not hack V-grooves or plaster over the grooves before painting.

As a result, rainwater entered the cracks and they grew to 4mm wide and 30mm deep.

More extensive, and expensive, repair works were carried out recently. A large portion of the compromised concrete structure, about 2m long and 60mm deep, was removed because the cracks had extended into the rebars.

These cases are classic examples of how a stitch in time saves nine.

Town councils must adopt more sustainable ways, like preventive maintenance, to keep their service charges low while ensuring the safety of residents.

Steven Lo Chock Fei

A version of this article appeared in the print edition of The Straits Times on December 21, 2016, with the headline 'Heed tell-tale signs of wall cracks'. Print Edition | Subscribe