Roof Waterproofing at St John’s Co-Cathedral, Malta

Roof Waterproofing at St John’s Co-Cathedral, Malta

Alchimica provided their Hyperdesmo Classic waterproofing solution to restore the Oratory roof at St John’s Co-Cathedral in Malta.

Commissioned in 1572, St John’s Co-Cathedral in Malta was designed by the Maltese military architect Gerolamo Cassar, and stands as a unique monument of international importance. The Oratory was built between 1602 and 1605, and was originally a plain rectangular construction. It was transformed in the 1680s including the installation of an altar and heavily gilt
carvings of the vault and arch in the apse.

The original Oratory roof was made of ‘Deffun’ a traditional type of screed mix used at the time for roofing. Over the years this was protected by 4mm reinforced bituminous membrane. This membrane was showing signs of deterioration and also needed repairs.

The waterproofing solution needed to:
• Be applied over the existing membrane so as not to run any risk in the event of any rainfall during the works
• Reinforce existing membrane and render the roof water proof
• Be as durable as possible
• Reduction of summer heat gain

Sparkbow Ltd with Alchimica S.A. recommended a solution using:
• Plastic Dowels for mechanical reinforcement of the old bituminous membrane to the building perimeter
• Hyperdesmo PB1K was used for the repair of the existing membrane
• Hyperseal LM25s flexible joint sealant
• Microsealer 50 was used as a primer
• Hyperdesmo Classic White together with a reinforcing geotextile

To the left hand side of the perimeter, dowels were covered by Hyperdemso PB1K to mechanically bind the membrane to the structure. As a precaution, the joints of the bituminous membrane needed reinforcing prior to the considerable restoration to be made on the lantern at the centre. Hyperdesmo Classic with geotextile was applied on the joints of the membrane on the Lower Oratory roof.

The membrane was repaired by Hyperdesmo PB1K prior to a full Hyperdesmo Classic application with geotextile.

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