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    Tough challenges at the House of Detention

    February 2023


They 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. 

When the existing surface of this 1,300 sq metre car park was gently broken away, it revealed the historic structure and an abundance of challenges. 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 and a substantial Civil Engineering Scheme was required to protect the structure and fill the voids. 

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 and the construction programme was behind schedule.  To bring the programme back on schedule, Cold Melt® DPM Primer was first installed over green concrete after only 3 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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