Having modernized their listed terraced Georgian house 15 years ago, our client again approached us to expand rather than move. We obtained consent to build under the entire garden in a design that rebalances narrow vertical family spaces for their brief for modern living - but without impacting the listed structure. We removed and then replaced the garden on top of a fully insulated, well-ventilated concrete and masonry box. A new volume, built from reclaimed bricks, houses new shower / utility space to make a third storey underpinning under the old rear ‘closet’ wing. By separating the garden completely from the house, this extruded masonry box is expressed vertically through fritted structural glazing that makes a bridge for access from the ground level to the walled garden; and the southerly aspect allows angled sun to penetrate the new lower level throughout the day.