RIW British Museum

The British Museum

Deep basement / boundary line construction waterproofing Case Study

01/11/2017

Opportunity

Design Requirements

• Architect: Rogers Stirk Harbour + Partners

The British Museum extension was developed as a

• Management Contractor: MACE

new Conference and Exhibition Centre to house a

• Project Contractor: Careys Plc • Building Description: An extension to the existing British Museum to form a Conference and Exhibition Centre to be used as a facility for events while housing a large collection of historical objects • Products Used: RIW Structureseal, RIW Cavity Drain R7, RIW Cavity Drain R20, RIW Sheetseal 226, RIW Toughseal, RIW Cementseal and RIW Waterstop

The Structure

Site Conditions

• R.C ground slab on pile caps

• Deep construction in a congested urban area

• Secant pile construction

• Water table classification defined as HIGH

• 4 storey full basement

large collection of historical objects, many of which are irreplaceable, while providing a facility to host events in.

The £135m project features a four storey basement, and RIW were invited by Rogers Stirk Harbour + Partners to provide specialist technical assistance with specifying the waterproofing strategy and design to protect the priceless artifacts and occupants within the building from ingress of water from the ground.

Detailing of the System With deep basement / boundary line construction, a

Cavity Drain R20 was sealed at the base and head

high water table and a retaining structure of secant

details on each intermediate floor using both Sheetseal

piles, a comprehensive waterproofing system was

226, as well as Toughseal, to form watertight joints. The

required for the British Museum. The initial application

system drains into channels, which are all linked to sumps

involved installing 2,000m² of Structureseal beneath

that are periodically emptied by automatic pumps.

the reinforced concrete basement slab, creating an

Due to the sensitivity of the project application, RIW

impervious layer based on bentonite clay. The bentonite

approved specialist waterproofing contractor Cast

within the Structureseal reacts with the ground water

Contracting Limited (CCL) installed the waterproofing

and swells to form a monolithic waterproof barrier.

and liaised closely with RIW and the project delivery team throughout.

As the substructure was built, 5,900m2 of Cavity Drain R7 was installed across the horizontal slabs, and 5,000m2 of the heavier duty Cavity Drain R20 directly to the secant piles. Cavity Drain is a flexible studded membrane designed to collect water entering the structure and channel it to a sump or collection point for disposal. RIW Cavity Drain meets the standards to achieve a Grade 3 (BS8102:2009) basement as required on this project.

Conclusion RIW was awarded the £400,000 contract to supply all of the integrated waterproofing solutions on the basis of its past experience working with both Careys and RSHP. As a result of the specialist contractor having design responsibility for the basement structure, RIW became involved throughout the pre-contract and installation phases of the project; providing scheme specific advice as well as a suite of site specific CAD details and construction drawings as the programme progressed.

The British Museum extension is now open for visitors and events.

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