Open-plan extension, decorated from bare plaster

This new open-plan extension came to us as bare plaster: a vaulted ceiling, three roof lanterns, a run of sliding doors onto the garden and one long uninterrupted space running from the kitchen through to the dining and living areas.

New plaster cannot simply be painted. It is porous, and it will pull the moisture straight out of a normal coat and leave you with a patchy finish that peels later. So the walls and ceiling were sealed with a properly thinned mist coat first, left to do its job, and only then built up in full coats. That step is invisible in the finished room, which is rather the point.

The raked ceiling and the roof lantern reveals were the fiddly part, all of it worked at height above a space that had to end up looking seamless. The finished extension is bright, clean and consistent from one end to the other, with the daylight from the lanterns falling across an even finish rather than showing up every join.