Buyer's guide

Flush sash vs casement windows — which suits your home?

Flush sash and standard casement are the two uPVC window styles we quote most across Caerphilly, Cardiff and the Valleys. They cost different money and they suit different houses. Here's a straight comparison.

The visual difference

A standard casement has a chamfered outer face — the sash sits proud of the frame. A flush sash sits perfectly level with the outer frame, giving the crisp square outline you see on original timber sash and casement windows. From five paces away, flush sash looks like painted wood; standard casement looks like uPVC.

Which suits which property

• Stone-fronted valley terrace, Edwardian bay, conservation street: flush sash.
• 1990s+ estate, modern semi, budget-driven refresh: casement.
• Rear elevation only: casement is fine, save the flush sash budget for the front.

Cost gap in real numbers

Roughly £120–£220 more per window for flush sash in the same colour and glass spec. On a 7-window front elevation that's £850–£1,500 — meaningful but usually the biggest kerb-appeal win in the whole budget. See our full window pricing guide for context.

FAQs

Do flush sash windows cost more than casement?

Yes — typically 20–35% more, per window. A £550 casement equivalent sits around £680–£750 in flush sash. The difference is mostly the deeper frame and the mechanical joints that give the square corner.

Are flush sash windows better for period homes?

For most stone-fronted terraces, cottages and Edwardian bays — yes. The flat outer face sits closer to the timber-window profile the house was designed for, so it doesn't 'read' as plastic from the street.

Which is more thermally efficient?

Broadly equal on paper — both hit A or A+ ratings with the right glass. Flush sash frames are slightly deeper so they cope with triple glazing more easily.

Can you mix flush sash on the front and casement on the back?

Yes, we do this often. Front elevation gets flush sash for kerb appeal; rear and sides get standard casement to keep the whole-house cost down.