Flush sash and standard casement windows are both casement designs. The difference is how the opening sash sits within the frame. A flush sash window sits level with the outer frame when closed, while a standard stormproof casement has a sash that overlaps and sits proud of the frame.
What is a flush sash window?
A flush sash window closes level with the frame to create a flat, seamless exterior face. This replicates the appearance of traditional timber joinery, making flush casements popular for period properties, cottages and conservation areas. The Residence Collection and Evolution Flush ranges offer modern timber alternative options with traditional detailing.
What is a standard casement window?
A standard stormproof casement has an opening sash that overlaps the frame, creating a raised lip and defined shadow line. This is one of the most common window styles in the UK and offers excellent weather protection.
What is the difference between flush sash and casement windows?
| Feature | Flush sash | Stormproof casement |
| Sash position | Level with frame | Overlaps frame |
| Appearance | Flat and traditional | Raised lip and shadow line |
| Best suited to | Period homes and cottages | Most modern and traditional homes |
| Weather performance | Very good | Excellent |
| Sightlines | Slimmer appearance | Slightly more substantial |
| Cost | Premium | Generally lower |
Which is better for weather protection?
Stormproof casements have the edge. The overlapping lip creates an additional weather barrier, making this style particularly suitable for exposed locations. Modern flush systems still offer very good performance through features such as advanced seals and drainage.
Are flush sash windows more expensive?
Yes, flush sash windows typically cost more because of their construction, detailing and manufacturing requirements. The premium can provide a more authentic appearance and better suit the character of a period property.
Which style suits your property?
- Period or Victorian property: flush sash
- Cottage or barn conversion: flush sash
- Conservation area: flush sash, subject to local requirements
- 1930s to 1980s home: either style
- New build or modern extension: stormproof or contemporary flush
- Exposed or coastal location: stormproof
Can you mix flush sash and casement windows?
Yes, although consistency matters. For example, flush windows could be used on a period front elevation while stormproof casements are used elsewhere. In conservation areas, planning requirements should always be checked first.
Which should you choose?
The best choice depends on your property, location and priorities. The difference is much easier to appreciate in person, so visit the WindowWorx Reading showroom to compare both styles and discuss your project.
