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No risk posed by Portcullis House roof, says study

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A year-long study into the causes of cracks in roof panels at the Hopkins-designed Portcullis House has completed

The technical study, which was commissioned by the House of Commons’ Strategic Estates team, has concluded that despite ongoing problems the roof will last its 30-year lifespan.

The study looked at movements in the roof over a year-long cycle and confirmed that it was structurally stable and posed no safety risk.

The report, costing £210,000, was commissioned after a number of problems were reported with the glazing over the £235 million building’s central atrium.

Computer modelling and more than 350 measuring points across the glazing confirmed that the cracking in the glazing panels had been caused by small movements in the roof which were transmitting the loads into the glass units.

The cracking in the glazing panels had been caused by small movements in the roof 

Seasonal variations and settlement in the building’s roof structure could also have been a factor as the fixings designed to accommodate any movements may have been taken to the edge of their tolerances causing the glazing units to fail.

It concluded that most of the settlement in the 15-year-old building’s structure had now probably already happened, and instances of breakages would reduce over time.

The study also predicted that up to £200,000 would be spent on the roof during the next 12 to 18 months, with the possibilty of a further £1.5 million over the remainder of its life when all the glass panels would be replaced. 

The strategy

The technical study recommended the following strategy for managing the maintenance of the roof: 

Immediate works (within 12 months)

  • Pack gaps that have opened up between some glazing support members, retighten glazing support rods and repair failed weather seals. 

    Cost up to £200,000

Medium term works (within five years) 

  • If further glass panels crack install bracing or ties to limit movement
  • Replace polycarbonate panels with glass if there is noticeable discolouration in the replacement panels
  • Replace all seals between glazing panels if there is noticeable misting within the glazing units

    Cost up to £1.5 million 

In the first year alone, 7,500 defects were reported in the office block, including loose door handles and cracked glass, according to a National Audit Office report in 2002, which examined its spiralling costs.

In 2005 a specialist crane was needed to replace four glass panels – at a cost of £100,000, with a further £34,000 spent replacing panels since 2009.

Before this report was commissioned there had been a number of attempts at fixing the roof’s problems but many were abandoned due to cost issues.

In 2008 a glazing consultant made recommendations to solve the problem, however the roof was not deemed to be a hazard, so no action was taken.

Since then a number of panels have shattered, with a glass panel found hanging from the frame and glass shards falling to the floor in one incident in 2014.

A special ‘anti-shatter film’ has been installed on the underside of each panel to stop pieces of glass falling to the floor and panels that cracked have been replaced with polycarbonate.

Until this report we couldn’t rule out the possibility of replacing the whole roof

Speaking exclusively to the AJ, Brian Finnimore, managing director of strategic estates, said: ‘We don’t want to do major works if we can avoid it. But until this report we couldn’t rule out the possibility of replacing the whole roof. We’re now reassured.

‘It’s a relief to all that the building’s roof will last out its design life of 30 to 35 years. We have to remember at the time this building was completed it was a very innovative and ambitious project.’

It had previously been reported that MPs were mulling legal action against the design and construction team behind the scheme, but Finnimore confirmed they would not be pressing ahead with this.

The findings of the study are now set to be presented to relevant parliamentary committees, including the House of Commons’ Administration and Finance Committees.

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