Glasgow's Red Road tower blocks 'too tough' for blast demolition
Some of Glasgow's iconic Red Road flats withstood a demolition blast last year because they were built with steel and were too tough, a report has found.
An inquiry was ordered after two blocks remained partially standing following the blowdown operation in October.
It said the contractor had identified discrepancies between the construction records and the size of steel used.
It concluded that Safedem had followed good practice and was "reasonable" to "err on the safe side".
The Red Road towers were the tallest residential buildings in Europe when they were built as social housing in the 1960s.
Their phased demolition was commissioned by social landlord Glasgow Housing Association (GHA) as part of its plans to regenerate the Balornock and Barmulloch areas of the city.
Previous demolitions took place in 2012 and 2013 and a plan to hold another, as part of the opening ceremony for the 2014 Commonwealth Games, was abandoned due to public opposition.
About 2,500 residents from nearby properties were moved to outside an exclusion zone before Safedem carried out the controlled blowdown on 11 October 2015.
The operation, however, was only a partial success as two of the towers were left partially standing.
A report into the failure concluded: "Safedem appear to have underestimated the robustness of the buildings.
"Whether this was from the explosives view point, the structural appraisal view point or a combination of both, is unclear."
The report said that the Red Road flats, unlike most other UK tower blocks built at the time, had been constructed using steel.
The report stated: "It should be noted that steel-framed residential structures are relatively uncommon in the UK.
"Unlike concrete structures, steel frames do not crush under impact from the debris above and tend to be more robust."
The report said that Safedem had examined "record drawings" from the city archives but found discrepancies between the 50-year-old records and the actual size of the steel columns in the buildings.
The report added: "The partial collapse of both 123 Petershill Drive and 10 Red Road Court were due to the variances in their construction and the exceptional difficulties in predicting the behaviour of these unique buildings.
"In this instance, Safedem had carried out detailed surveys and noted a number of discrepancies between the surveyed buildings and the design drawings and therefore appear to have followed good practice.
"Bearing in mind these discrepancies, it would have been reasonable for their designers to take a cautious view of the structures and err on the safe side, regarding pre-weakening."
Following the failure, the towers were brought down using high-reach machinery.
GHA regeneration director, David Fletcher, said: "We're on track to have the area completely clear by late 2017 as planned and would like to thank nearby residents again for their patience and understanding while we carry out this work.
"Once cleared, the area will be turned, short-term, into a safe and attractive green space for the community while plans for housing and amenities are brought forward in phases.
"We've consulted with local residents at community events and their views are helping shape the future regeneration plans."