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Liverpool’s world heritage skyline gets protection

How the rooftop cupolas have been safeguarded at the Royal Liver Building.

When it comes to heritage credentials, they don’t come much more prestigious than Liverpool’s Royal Liver Building.

The Grade I-listed office is one of Liverpool’s ‘Three Graces’ and part of the UNESCO World Heritage Maritime Mercantile City.

Originally constructed as the home of the Liver Assurance Company, the Royal Liver Building was one of the first buildings in the world to be constructed using reinforced concrete when it was completed in 1911.

The building’s façades have a cupola in each corner, with a mini cupola on the four corners of two clock towers.

These 12 domes were the subject of a recent project using Kemper System’s 1K-PUR cold liquid-applied waterproofing system.

Challenging work at height

While Kemper’s wet-on-wet waterproofing membranes are designed for application with a single liquid resin-reinforcement fleece-liquid resin process, a number of factors made the Royal Liver Building project much more challenging.

First, it stands almost 100 m tall to the top of its spires and more than 50 m to its main roof.

“The building’s height and its exposed waterfront location created significant working at height challenges”

For many years, it was Europe’s tallest storied building and it remains the fourth tallest building in Liverpool today.

That height and the building’s exposed waterfront location created significant working at height challenges for roofing contractor K Pendlebury & Sons, with the team working as much as 14 storeys up.

The intricate design of the roof also means many areas are hard to reach.

Specialist restoration main contractor Quadriga had to erect scaffolding on a small area of the roof at a time so that an upgrade could be carried out to localised areas beneath each cupola.

Access influences design

A larger stretch of roof on the elevation facing Liverpool’s Strand was also incorporated into the scheme to capitalise on the accessibility created by the scaffolding.

For the flat areas of the roof, the contractor was able to install an inverted insulated roof build up, using Kemper System’s Kemperol V210 cold applied waterproofing system to waterproof the substrate, followed by insulation and then paving.

The domed cupolas, which have a 2 m-high vertical surface before the structure starts to curve and gradually become flat over the top, required a slightly different approach.

“Installation conditions were difficult and the quality of project delivery had to be delivered in line with strict listed building guidance”

Following trials carried out by the contractor, Kemperol 1K-PUR was specified for the domes as it can be applied directly from the tin without the need to mix on site.

It is also more viscous than V210, making it easier to work with on the vertical surfaces.

No margin for error

There is no margin for error in a project like this, where installation conditions are difficult and the quality of project delivery must be delivered in line with strict listed building guidance.

The trials ensured the best approach was agreed in advance with the building’s management company CBRE and English Heritage.

The cupolas are of concrete construction and have been protected by various waterproofing systems over the years, but water ingress was becoming a problem, leading to areas of concrete failure.

Repairs were needed to return the surface of each cupola to its original domed shape prior to installation of the new waterproofing membrane.

This was carried out using one of Kemper’s epoxy primers mixed with graded fillers to make a repair mortar that could be used to build up the eroded areas of concrete.

The same Kempertec primer was then used to prime the substrate before the Kemperol 1K-PUR resin was applied.

Kemper’s 120 g reinforcement fleece was cut to size and shape on site and laid onto the wet resin.

Site workers immediately applied further resin over the top to allow complete saturation of the reinforcement fleece in a single wet-on-wet process that cured to provide a seamless, monolithic membrane.

For the larger cupolas, the scheme also involved scroll features and termination details, requiring painstaking application of the system around the solid granite mini scrolls that surround each of the smaller cupolas.

Mark Bruchez is technical director at Kemper System

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