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Tough challenges at the House of Detention

2 mins

Challenges don’t come much tougher than a car park over the basement roof of a 17th century London prison, known as the House of Detention.

Due to previous poorly-installed waterproofing, the car park required extreme refurbishment and  waterproofing works.

The defective waterproofing was allowing water ingress into the ancient structure below, causing erosion and green fungus decay to the brick surfaces. The proposed works included forming a solid structure over the 17th century brick vaults with falls to a drainage collection system, fully waterproofed with PROTEUS WATERPROOFING’S exclusive Cold Melt®® system.

When the existing surface of this 1,300 m2 car park was gently broken away, the ground floor prison cell floors were exposed with deep voids down to the vaulted ceiling. This meant the structural designs had to be revisited.

Proteus product used on Clerkenwell Basement
Proteus product used on Clerkenwell Basement

Engineers were able to redesign a suitable substrate for the vaulted ceiling to include a reinforced concrete cambered slab with perimeter curbs to channel the water to outlets, solving problems ahead of construction. Once the old substrate had been carefully removed, the newly-designed reinforced concrete base, perimeter curbs and outlets were installed, and the waterproofing works could commence.

However, the design changes to the structure meant valuable time was lost. To bring the programme back on schedule, Cold Melt® DPM Primer was first installed over green concrete after only three days. The concrete below the primer, now protected from the elements, was allowed to continue its chemical hydration process and cure in its own time.

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