Capella: All clear at King’s Cross

Affordable homes to the south

Affordable units face out onto Keskidee Lane in close proximity to the office building opposite. To safeguard privacy and to offer views of Lewis Cubitt Park, we staggered units to face east. These flats have full-height doors and offer park views from their balconies, affording dual aspects to nearly all of the social rented units. Deep reveals to doors and windows ensure flats do not have undue heat gain, verified by thermal modelling by our sustainability consultant, Hoare Lea. Though smaller than on the market sale east elevation, the Nordan windows are still generous, measuring 2.3m wide by 1.8m tall. Windows have raised sills sat above brick soldier courses and low balustrades. As these are larger, family units, we were mindful of the everyday domestic mess that just happens. Higher sills keep this out of sight and give greater levels of privacy with less overlooking to bedrooms. 

House on south-east corner

Part of the complexity of this project was in ensuring the aesthetic compatibility of the Nordan doors and windows with the Wicona Wictec 50 curtain wall cladding system used elsewhere on the building – for rooftop penthouse units for instance. It reminded us of the importance of control samples, helping us resolve performance requirements with the required aesthetics and material quality. The two-storey penthouse units are prominent, notably on the south ‘gable’. As it was double height, at 5.93m, we used the Wicona aluminium system but stiffened with a small steel section cloaked in its frame profile and with bridging over the door openings. In some instances, Kawneer doors were also installed with Wicona cladding on the full-height ground floor retail and entrance area glazing.

Ground-floor sale amenity 

At ground level, with market sale and social rented lobbies as well as retail units, it was important for us to optimise the relationship to the park and maximise views into as well as out of the block. So we were keen to increase the visible light transmittance on the glass,  minimising external reflectivity, and wanted to keep the detailing simple and crisp. With the need to provide air intake and venting to retail units and lobbies, a plenum is situated above the glass behind the horizontal clerestory louvres. Structural uprights are concealed behind the horizontal band of louvres for the elevation to appear minimal and well detailed. On a smaller scale, we use a similar approach for the apartments’ assisted ventilation. Hidden above door frames and windows you’ll find a concealed air intake hidden within a slot detail in front of an insulated plenum box. It’s a triumph!

Upper level two-storey house

The two-storey penthouse units give a full idea of what we achieved elsewhere. All doors have level thresholds to balconies with porcelain tiles running through and out to give visual continuity. You can see the steels covered by the Wicona aluminium sections here, helping achieve the dramatic double-height internal volume, overlooked by the mezzanine level. Above the beam is the cladding and below are the Nordan composite windows and terrace doors. We insisted the glass had a visible light transmittance of greater than 0.68 with minimal external light reflectance and 0.46 solar energy transmittance (g-value) and, for consistency, that both systems came from the same glass supplier.

Sale flats and entrance on east

We won the competition for the project in November 2020 and designed the building on behalf of Argent (now Related Argent) for Stages 1-3. We were then novated to the contractor, Laing O’Rourke, at Stage 4a for detailed design. The client was keen that the external envelope of prefabricated scalloped and brick-faced concrete panels was detailed by us as the contractor had advance ordered them and had to comply with their fabrication time slot as part of its cost bid. We chose cream concrete and green-painted windows to both give lightness and to respond to the vibrancy of its park setting. Apartments with large bolt-on balconies create depth and texture on the principal elevation, and here we specified generous full-height timber composite windows and doors from Nordan’s Ntech range with a bespoke textured polyester powder coating. The double-glazed composite aluminium units gave optimal thermal performance over the facades – achieving 0.39 W/m2K – as well as the internal qualitative warmth of painted white timber. For the green colour, RAL 6011 HR, we chose a matt silicate finish by IGP, which gave a greater depth of colour than standard PPC finishes. This was a prerequisite in awarding the contract to Laing O’Rourke and Nordan.

In numbers 

GEA 21,840m2 
Apartments (33 different types) 176 
Social rented 32% 
Thermal performance over facades 0.39m2K
Reduction in carbon emissions via link to KXC district energy network 48%