Architect AHMM sent back to the drawing board to add second staircases, a new facade and air conditioning

AHMM has been sent back to the drawing board to overhaul a twin-tower scheme in Canada Water after the plans were hit by three separate regulatory changes.

The practice has submitted several amendments to Southwark council for the proposals, which are set to occupy Zone F of British Land’s 53-acre Canada Water masterplan, one of the biggest regeneration sites in London.

AHMM Canada Water 1

The scheme consists of two towers linked by a podium

An initial set of plans were granted detailed approval in July last year and consist of a pair of 36- and 33-storey towers linked by a nine-storey podium, containing 410 homes, 37,500 sq m of workspace and 2,200 sq m of flexible retail space.

But the scheme has been hit by a raft of new building regulations, including the government’s plan to mandate second staircases in residential towers above 18m in height.

The changes include second stair cores in each tower, a better performing facade to comply with new Part L regulations, which require buildings to have improved energy efficiency, and air conditioning in all flats to comply with Part O regulations, which aim to reduce overheating. Both parts O and L came into force in June 2022.

The practice has rejigged the internal layouts of the towers to fit in the second stair cores, resulting in a loss of around 560 sq m of floorspace and changes to the types of homes provided, although the scheme will now provide one additional home overall compared to the original plans.

The size of the tower cores have been increased by around 18cm on all sides, although AHMM said this will have a limited impact on the design of the apartments.

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Extra doors have also been added to the circulation areas of the cores to create a sealed zone in the event of a fire, and new smoke extractors have been added to each separate circulation space.

The project team includes planning consultant DP9, project manager Aecom, QS Gardiner & Theobald, structural and facade engineer AKT II, transport consultant Arup and MEP, vertical transport and sustainability consultant Sweco.

It is the second time AHMM has been told to revisit its plans for a major scheme this year because of the second staircase rules, following its redesign of the 1,800-home redevelopment of the O2 Shopping Centre in North London for Landsec.

The government’s proposed mandate for second staircases, unveiled in a consultation in December last year, initially applied only to buildings above 30m in height.

This threshold was then adopted with immediate effect by London mayor Sadiq Khan in February, unleashing a wave of major tower scheme redesigns across the capital as developers scrambled to comply with the rules.

Housing secretary Michael Gove then lowered the threshold to 18m last month in a move expected to cause further headaches for housing developers, although RIBA hailed it as a “huge win” for fire safety standards.