A Private View: A slate-clad structure completes this personal family portrait in Lambeth

Tall and commanding, this Georgian terraced house on south London’s Lambeth Road harbours a secret: an unexpected extension of indeterminate age that completely transforms the ground floor and garden beyond. Clad in reclaimed slate tiles and conceived as two separate spaces – a garden room and gallery – it nestles, grotto-like, into its newfound position, a singular, enticing entryway to a secluded world of stately trees.

To deftly integrate this idea into a building so steeped in history calls for a thorough understanding of both the fabric and the unique atmosphere of this richly layered home. Enter architect owner, Grace Fletcher, who has been visiting the house since she was a child.

The townhouse was purchased by Grace’s grandparents in the 1960s. Her grandfather – grandson of the celebrated, 19^th-century architect, Edwin Lutyens – carved out a truly mid-century home amid the genteel bones of the building. Seeing it through its various iterations proved invaluable for Grace, who embarked on the renovation project in 2019: “I came here as a grandchild, so, in some ways, having all that history and the memories was useful: I knew where to look to begin to uncover things …”

Grace – who partnered with Stuart Archer and Sarah Braun of the architecture practice, Archer + Braun – balanced the build with her own architectural studies. “A lot of the academic work I was doing at the time was very abstract,” she recalls. “Being able to then come to the site and experience the real thing was a good combination.”

Familial connections run through the fabric of this house, presenting Grace with a uniquely personal conundrum when deciding what to restore and what to replace. Structurally, the original ridge beam that defined the centre of the roof has been repurposed as garden benches. At a smaller scale, a strip of mid-century wallpaper chosen by Grace’s grandparents has been recovered and reinvented. Grace’s mum, an erstwhile wallpaper designer for Colefax and Fowler, worked with Hamilton Weston to create a similar, subtly modernised version of the design.

In a continuation of that theme, the Ballachulish slate that clads the external wall of the extension were reclaimed from Grace’s aunt’s house in Scotland. Each piece has been painstakingly selected and laid from smallest to largest, “like a huge jigsaw.”

“Something I really like about old buildings is how embedded they become in their site,” Grace explains. “I tried to be sensitive to that, so the materials we chose do work in similar ways. Whether it’s the copper roof on top of the extension, the light lime render outside, or the slates – they all respond to the environment. I think they give a softness that grows with the old building.”

Nature permanently inhabits the house, invited in through its many doors and windows. (Grace points out the direct sight line created from a spot between the stately Tree of Heaven and Judas trees, through to the front door.) In the extension, a rainwater collection system is used to tend to houseplants great and small: “Rainwater comes down from the roof and enters a diverter that filters it before it goes into a rainwater tank in the wall,” Grace explains. “When it rains, we can just leave the taps on and water the plants that way.”

Designed for plants and people alike, the new space has a loosely defined function. “A lot of new extensions come with a big kitchen island in the middle of them,” says Grace. “I think, in the end, deciding against that has meant that the space remains flexible. Not over-designing it has meant that it can be used in lots of different ways.”

“I love looking back from the garden and seeing how the extension fits in,” Grace concludes. “It feels like it belongs in that view, which is what we were trying to achieve. I suppose you don’t really know if it’s going to work until you’ve done it.” Having lovingly covered it in the last of the pink blossom from the Judas tree, it seems the garden has given the extension its seal of approval.