Good renovation advice is almost always retrospective. You have to make the mistakes first. Room by Room is a new series from Glassette where we ask designers and homeowners to walk us through a single space: what wasn't working, what they spent too much on (and whether it was worth it), and what they'd tell you before you pick up a sledgehammer.

For the latest instalment of Room by Room, we spoke to Corey Hemingway, co-founder of design-led estate agency Hemingway+K, about the kitchen extension of her 1960s London townhouse. What started as a small, dingy space became a warm, light-filled room designed to do everything at once: cook, work, host, and connect seamlessly to the garden beyond.

Twelve months in the making, the project came with its share of surprises - deeper foundations, escalating construction costs, and the occasional challenge of being, in Corey's words, a "tyrannical perfectionist". Along the way, she learned the value of trusting contractors, following instinct when choosing materials, and investing in the elements that shape a room's atmosphere.

From Douglas fir walls and butter-yellow joinery to the Accoya sliding doors that frame the garden, Corey takes us through the decisions, splurges and lessons behind her favourite room in the house.