SINGAPORE - The concrete flooring behind several Housing Board blocks in Woodlands was found covered in algae shortly after it had been repaved, prompting residents to alert the town council.

A photo shared on forum discussion thread Reddit on Sunday (Nov 25) shows dark green patches next to the void deck of several blocks in Woodlands Street 81.

The Reddit user said that it has been "months" since the algae appeared.

It is not clear when the photo was taken.

Several other Reddit users said that the algae growth could be a potential fall hazard especially for the elderly folk living in the area, who could slip and end up injuring themselves.

In response to queries, the Sembawang Town Council said that the affected area is near blocks 870 to 882, as well as around blocks 801, 802 and 804 near Republic Polytechnic.

The town council spokesman said that the algae growth was caused by poor workmanship from the re-rendering of the concrete surface. The re-rendering works were carried out between October last year and April.

"We have discussed with the contractor in charge of the re-rendering, and it has agreed to carry out rectification works," the spokesman added.

Re-rendering refers to hacking off the concrete surface and re-applying fresh concrete over it.

Such concrete surfaces face natural deterioration, and will sustain wear and tear over time.

The spokesman said that it has asked the contractor to increase the frequency of the surface washing from once a month to every fortnightly in the meantime.

Anti-fungicidal chemicals will also be used to slow down algae growth while rectification works are being carried out.