Window Woman guides
Flush vs storm-proof casements
A small detail that makes a big difference, and one of the most common reasons replacement casements are refused in listed buildings.
Flush casement: the traditional window
The opening sash sits within the frame, so when it's closed it is level with the face of the frame. The look is clean and flat, with slim, even sightlines, and the opening and fixed sections match.
Storm-proof casement: the modern window
The opening sash overlaps a lip on the frame and sits proud of it. This type became standard in the 20th century because it was cheaper to weatherproof. The result is a chunkier, stepped appearance, with opening sections that look visibly different from the fixed ones.
How to tell them apart
Look at a closed window from the side. If the opening part sticks out beyond the frame, it's almost certainly storm-proof.
Ironmongery matters too
Traditional casements use a stay and peg, or a cockspur fastener. Heavy friction hinges and chunky modern handles change a window's character just as much as the frame does.
The good news
- Good modern joinery can make flush casements that are fully weathertight
- There's no need to compromise on appearance to get a sound, draught-free window
More guides
These guides are general information for England and don't replace advice specific to your property or your local planning authority.