Alumasc provide Victoria & Albert Museum with the ideal Hybrid Waterproofing Solution

The Victoria and Albert Museum, London, is the world’s largest museum of decorative arts and design, housing a permanent collection of over 4.5 million objects.

A brand-new entrance, ceramic tiled courtyard and purpose-built subterranean 1,100sqm gallery for temporary exhibitions was to be built. The new courtyard will provide an open-aired space right in the centre of South Kensington.

This area needed a durable, reliable waterproofing solution that would provide a solution to the various threshold heights throughout the project.

A Hydrotech system was used throughout which incorporated a typical inverted roof build up and hybrid construction incorporating Foamglas insulation. The 1200m2 installation was carried out by Alumasc Registered Contractor, Knight Asphalt.

What is a Hybrid build up?

The hybrid specification offers the combined benefits of incorporating a superior thermal performance insulant i.e. PIR or Foamglas with a hot-melt waterproofing, assuring that the specification is compliant will all current relevant standards, codes of practice, and the Building Regulations to provide a secure, free draining and completely weathertight roof.

Hybrid Insulation System

As you will see from the above graphic the thickness of PIR (Polyisocyanurate) required when compared to the adjacent XPS (Extruded Polystyrene) to achieve a given u-value target is substantially less. An example of where this detail may be used is on a balcony where upstand heights are to be kept to a minimum with a flush threshold.

For stepped construction(s) provision for drainage would ideally need to be allocated to both zones. The step transition can occur in various ways e.g. a two-tier step in the paving utilising adjustable supports, a timber batten upstand to which the membrane will encapsulate finished level with the XPS, or alternatively incorporation of a kerb stone as illustrated in our sketch which may be more aesthetically pleasing.

V&A utilised Foamglas in favour of PIR in this instance because of its exceptional fire performance and dimensional stability.

For further product information about Alumasc’s various Waterproofing Systems click here or call our technical team on 03335 771 500.

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