Modern Glass Box Extension

A black-framed glass box in Bowdon, Cheshire — glass roof, corner glazing and wide Cortizo sliding doors set against warm brick.

📍 Bowdon, Cheshire

A plain summary of the 2027 Part L changes as they affect windows, doors, rooflights and glazed extensions — dates, transitional rules, the numbers that moved and the ones that didn't, and what to do on live projects now.

Part O caps the glazed area of every new home room by room, by orientation and ventilation. The moderate-risk figures for Liverpool, Manchester and the North West, what happens when a design exceeds them, and how to keep the big glass.

From 24 March 2027 every window on a new home must be calculated at its real size with every frame component included. What changes, who it catches, and how steel, aluminium and structural glass get to 1.2 W/m²K.

Most of the houses we glaze are old. Georgian terraces in Liverpool, Victorian villas in Cheshire and South Manchester, stone farmhouses in Lancashire and the Dales. Here is why structural glass tends to be the extension that gets approved on a period home, and how the old wall and the new glass are made to meet.

People planning a glass box, link or corridor usually want to know two things: how long it takes and what happens in between. This is the sequence every one of our North West projects follows, from the first site visit in Cheshire, Lancashire or Merseyside to the day the glass goes in.