UPVC Flush Windows – Sleek Minimalism, Superior Thermal Performance
The type of windows represent a distinctly modern interpretation of the casement window concept. Unlike traditional casement windows where the sash projects slightly outward from the main frame face, a flush window has its sash and outer frame sitting on a single, level plane - creating a flat, uninterrupted surface appearance from the exterior. This minimalist aesthetic has made UPVC flush windows the preferred choice for contemporary residential architecture, modern self-build projects, and architects seeking clean horizontal sightlines that align with the minimal design language of current-generation homes.
The type of windows combine this refined exterior profile with all the thermal advantages inherent to uPVC framing - multi-chamber profiles, seamless weather sealing, and compatibility with the full range of high-performance glazing configurations.
The Flush Casement Design
In a conventional casement window, the sash frame sits proud of the outer frame by approximately 8–12 mm. In a UPVC flush window, the sash is rebated so that its outermost face aligns with the outermost face of the outer frame. The visual result is a flat, frameless-looking window from the exterior - the division between sash and frame appears as a simple shadow gap or narrow groove rather than a stepped profile.
This flush design creates several practical and aesthetic advantages:
Slim Integrated
From a distance, the window appears thinner and more integrated into the wall
Smooth Drainage
Rainwater run-off is more consistent across the facade without the shadows created by protruding sashes
Easy Clean
The flat exterior surface is easier to clean and less prone to trapping dirt in recesses
Clean Minimalist
The aesthetic reads as more contemporary and minimalist than conventional casement designs
Technical Specifications
| Profile Material |
uPVC (Multi-Chamber) |
| Profile Wall Thickness |
1.6 mm – 2.0 mm |
| Profile Width |
70 mm – 120 mm (frame and sash combined) |
| Glass Options |
DGU / TGU · Low-E · Argon-filled |
| Glazing Thickness |
28 mm – 44 mm |
| Air Leakage |
≤ 0.1 cfm/ft² | Class 4 (EN 12207) |
| Water Tightness |
E1000 Pa (EN 12208) |
| Wind Load |
≥ 2000 Pa | Class C5 (EN 12210) |
| Sound Insulation (Rw) |
Rw 38 – 46 dB |
| Thermal Performance |
Excellent |
| Available Materials | Vinyl / uPVC |
| Certifications |
CE, NFRC, AS 2047 |
Thermal Performance
uPVC's multi-chamber profile cross-section provides outstanding natural thermal insulation without the need for inserted thermal breaks. SKATE's UPVC flush window profiles contain multiple hollow chambers within the extrusion - each chamber trapping air and reducing the overall thermal conductance of the frame. Combined with double Low-E argon glazing, the complete window system achieves U-values in the range of 1.3–1.6 W/m²K, while triple Low-E argon configurations reduce this further to approximately 0.9–1.1 W/m²K - meeting passive house thermal requirements in the frame-and-glass assembly.
Weather Sealing
The flush casement design is achieved through a specifically engineered gasket system that seals the sash against the outer frame on a flat plane rather than a stepped rebate. This requires precision gasket geometry and compressed-fit hardware to maintain weathertightness equivalent to - or better than - conventional casement designs. SKATE's flush window gaskets are manufactured from EPDM rubber, UV-stabilised for long-term elasticity, and designed for a minimum 25-year service life.
Hardware Selection
The hardware used on UPVC flush windows is critical to the flat-face aesthetic. SKATE specifies concealed hinges that are fully recessed into the frame profile, exposing no external hinge arm when the window is closed. Locking handles are available in a low-profile, flat-face style that complements the flush design - available in satin chrome, brushed nickel, matt black, and brushed gold finishes to coordinate with the building's interior and exterior hardware scheme.
Multi-point locking is standard across all SKATE UPVC flush window sizes, providing simultaneous engagement of lock points at the top, bottom, and strike side of the sash perimeter.
Colour Options
SKATE UPVC flush windows are available in white, cream, and a range of solid-colour foil-laminated finishes including Anthracite Grey (the most popular contemporary colour), Basalt Grey, Agate Grey, and Jet Black. Dual-colour options - typically grey or black exterior with white interior - allow the contemporary exterior aesthetic to be combined with a bright, light-reflective interior finish.
Ideal Applications
They are widely specified for: contemporary self-build homes; modern housing estate developments; urban apartment buildings; architect-designed residential projects; passive house and near-zero energy building specifications; barn conversions and agricultural-style residential buildings; and any project where the window must disappear into the facade rather than project from it.
Frequently Asked Questions
Q: Are UPVC flush windows harder to seal than conventional casement windows?
A: They require more precise manufacturing tolerances but - when produced correctly - achieve equivalent or superior weathertightness. SKATE's production process is controlled to ensure consistent gasket compression across the full sash perimeter.
Q: Can UPVC flush windows be combined with fixed lights in the same frame?
A: Yes. Fixed lights and operable flush sashes can be combined within the same outer frame, creating seamless window assemblies of any width.
Q: Are concealed hinges as durable as external strap hinges?
A: Yes. SKATE's concealed hinges are manufactured from stainless steel or zinc-aluminium alloy and are tested for a minimum of 50,000 open/close cycles - equivalent to more than 30 years of daily use.
Why Choose SKATE
SKATE produces UPVC flush windows at our direct 160,000 m² manufacturing facility, supported by 29 years of fenestration engineering experience, CE, NFRC, and AS 2047 certification, and global supply to over 30 countries. Our factory-direct model delivers consistent quality without trading markups.
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