Smugglers Way, Wandsworth

Leviat’s Halfen thermal break connectors make light work of complex balcony fixing at London’s new housing mega-development.

One of London’s largest new mixed-use development schemes, Smugglers Way is set to deliver a total of 554 sustainable built-to-rent and affordable apartments across 13 blocks, on the former 1.41 hectare site of an old B&Q superstore.

A flagship for the regeneration of this area of South West London, the blocks range in height from 8 to 16 storeys, and are arranged with 3 podium levels, providing over 8000m² of business, retail and restaurant space, as well as a range of amenity and health and fitness spaces for residents.

Designed to achieve a BREEAM Excellent rating and Home Quality Mark 4 standard, architects, Hawkins Brown, have focussed on sustainability throughout, with many apartments offering dual and treble aspect balconies to maximise the living space and optimise natural light and ventilation.

The challenge

A combination of steel cantilever balconies and insitu concrete balconies had been specified throughout the various blocks to add depth and visual interest to façades.

Whilst it was crucial that both balcony types were effectively thermally broken to minimise heat transfer across joints, the main challenges were presented by the triangular concrete balconies, which were largely positioned at 45 degrees across the building corners and supported from columns, to create a feature.

Consulting Engineer, Ramboll, approached Leviat with two major challenges. Firstly, how to provide the special tension connection required to tie the columns supporting the balcony slabs to the main structure via a thermal break. This was made more complicated by the design of the internal edge beam and a sizeable balcony step, which meant it could not be achieved using a standard thermal break connector solution.

Secondly, there was the practical problem of assembling the thermal break threshold on site, as the orientation of the thermal break, at 45 degrees to the balcony and internal slab reinforcement, meant standard products would not fit together within the formwork.

The solution

The Leviat technical team provided a solution using their Halfen HIT thermal breaks - high capacity units specially designed to transfer bending moments and high positive and negative shear forces in complex balcony structures.

To overcome the challenges associated with the insitu concrete balconies, the team developed a bespoke solution using Leviat’s Halfen HIT-HP MVX connector, a symmetrical connector that is installed independently of the main slab or balcony direction and includes 80mm of insulation to minimise heat transfer. The solution involved producing a slender version of the connector with a headed reinforcement, that could be interspersed between standard shear connections to provide the required support.

To overcome the casting problem, the team also developed special covers that enabled the Halfen HIT thermal break to be seamlessly assembled at the required 45 degrees within the formwork, prior to concrete pouring.

Specialist Design & Build Contractor, McAleer & Rushe subsequently installed a total of 1700m of the bespoke Halfen HIT-HP-MVX thermal breaks throughout the project to secure the concrete balconies.

To maintain the thermal performance of the external envelope, new stainless steel Halfen HIT-HP-SDV high performance steel to concrete thermal breaks were also used to provide adjustable, easy-to-fix, high load transfer connections for the steel cantilever balconies in more compact spaces – one of the first times this new connector had been used on a major project of this kind.