A structural engineer says a construction blunder at The Pavilia Farm residential complex may have involved the wrong type of concrete being used, or the right concrete put in the wrong place.
Property developer New World Development said on Thursday that two towers at the highly-popular project under construction in Tai Wai will have to be torn down and rebuilt, after they failed concrete strength tests.
New World said the concrete in some of the walls did not meet the requirements of the approved design.
Speaking on an RTHK programme, structural engineer Ngai Hok-yan said there is not enough information at the moment to conclude what has gone wrong, but there might have been some human error involved.
The engineer said plants rarely run into problems manufacturing concrete as their production process has been computerised and they also carry out many tests every day.
He said one theory is that concrete with a compressive strength of 45MPa was used in the construction process, instead of that with a higher compressive strength of 80MPa.
The megapascal (MPa) measurement tells inspectors how much pressure can be applied to concrete before it cracks or fails. The higher the MPa, the stronger the material is.
Ngai said while it would be technically possible to rectify the mistakes by reinforcing the structure of the blocks, the space inside the apartments would be compressed by the introduction of thicker, reinforced walls. He said this may affect the confidence of the property owners.
Engineering sector lawmaker Lo Wai-kwok said it appears that the construction blunder at the third phase of The Pavilia Farm might be down to poor supervision at the construction site.
He said tests on concrete are usually very stringent and he doesn't think that this is the major cause of the incident.
The lawmaker urged the contractor involved and the Buildings Department to carry out a thorough probe, looking into issues such as whether there was a misunderstanding regarding the design plans or a mixing up of different types of concrete. He added that they should also find out why it took so long before the problem was discovered.
"I think the chance of design error may be low, because all the design drawings etc. have to go through very rigorous checking and also assessment by government departments. So the chance of some human error in the on-site supervision is one of the directions that they should carry out the investigation," he said.
But Lo also said he believes the property developer has taken suitable rectifying measures, and that the incident shows there is a mechanism in place to monitor the quality of construction projects in the city.
Meanwhile, the chief executive of Midland Realty's residential division, Sammy Po, said although many buyers are concerned about the safety scare, he had not yet heard of any deciding to terminate their deals.
New World said the project’s completion date will have to be pushed back by around nine months. It said the almost 850 buyers affected will be given the option of either carrying on with their deals or terminating them, with compensation to be provided either way.
Po said the compensation offered would be enough for buyers to rent another place in the meantime. He said he believes most buyers would be willing to wait for another nine months unless they need to move in soon.
He also said he believes the incident will have little impact on people’s confidence in New World, as it has owned up to the blunder and offered reasonable compensation