Specifying a uPVC casement window goes beyond choosing the colour and the size. The uPVC casement window specification that actually determines how the window performs — how it seals, how it handles weather, how long the hardware lasts — sits in the profile series, the chamber design, the hardware selection, and the glazing configuration. These aren’t details that show up in a showroom brochure, but they’re the details that separate a window that works quietly for 20 years from one that needs repair in three.
Most buyers discover these specifications only after they’ve experienced a problem — a window that whistles in wind, hardware that corrodes, or a corner joint that starts to open. The better approach is to understand the uPVC casement window specification before installation.
Duron uPVC manufactures profiles used across India for casement window fabrication. Their 60-series profile systems are engineered for Indian climate conditions with the hardware compatibility and dimensional standards that fabricators need for consistent results. This guide covers the full specification.
uPVC Casement Window Specifications
A complete uPVC casement window specification covers the following parameters:
Profile series: The frame and sash profile depth — typically 60mm, 70mm, or 80mm.
Chamber design: Single, multi, or reinforced chamber construction.
Wall thickness: The minimum thickness of each profile wall in millimetres.
Hardware: Hinge type, locking mechanism, handle, and operating hardware.
Glazing: Glass type, thickness, and the glazing bead system holding it in place.
Sealing: Gasket type and placement for weather and acoustic performance.
Corner joints: Method of frame and sash corner connection.
Understanding each of these parameters is what makes a uPVC casement window specification meaningful rather than superficial.
Key Components of uPVC Casement Windows
Profile System
The 60 series uPVC profile is the most widely used standard for residential casement windows in India — a 60mm frame depth that provides adequate rigidity for standard window spans without excessive material cost. Larger spans or heavier glazing units typically require 70mm or 80mm profiles.
Multi-chamber uPVC profile design is the primary structural differentiator. A multi-chamber profile design creates air pockets between chamber walls that resist thermal bridging and improve rigidity compared to single-chamber profiles. Better profiles have 3–5 internal chambers across the frame section.
Profile wall thickness mm is specified in the design standard. European Norm (EN12608) specifies minimum wall thicknesses for uPVC profiles by impact class. The main walls of a quality profile should be minimum 2.8mm thick — thinner walls reduce rigidity and long-term dimensional stability.
uPVC Window Steel Reinforcement
All load-bearing sections of a casement frame — particularly the frame header and sill, and the sash section opposite the hinge — should have uPVC window steel reinforcement. A galvanised steel insert is fitted inside the profile cavity, typically 1.5mm–2mm thick.
Steel reinforcement prevents the frame from deflecting under the window’s own weight and under wind load. For casement windows above 900mm in width, reinforcement is critical. Without it, the sash will sag at the hinge-side corner, causing alignment problems and seal failure over time.
EPDM Gasket Window Sealing
The EPDM gasket window seal runs around the perimeter of the sash where it contacts the frame. EPDM maintains flexibility across India’s temperature range — from sub-zero temperatures in North India winters to 45°C+ summer heat — without hardening or cracking. PVC gaskets harden over time and lose their seal; EPDM gaskets don’t.
A double gasket arrangement — one on the frame, one on the sash — provides better weather exclusion than a single gasket system and is the standard in quality casement window specification.
Glazing Bead uPVC
Glazing Bead uPVC System Locks the Glass Unit into the Sash Glazing Bead uPVC systems generally have snap-fit bead profiles that click into the sash rebate, once the glass unit is installed. A good glazing bead uPVC system will hold the glass on all four sides with uniform clamping force. An inferior bead design will allow the glass to move in the rebate, putting pressure on the silicone sealant.
Friction Stay Hinges
Outward opening casement windows will be fitted with friction stay hinges as standard. A casement window hinge holds the sash at any point in its open position, as opposed to allowing the sash to hang freely. This gives some control over air flow without needing to use an additional stay arm.
Friction stay hinges come in a range of heavy-duty ratings – often 80kg or 130kg for domestic casement windows. Heavier glazing units including large double-glazed panels will have a higher ratings. An undersized hinge will cause the sash to sag in time and compromise the seal at the same time as affecting the locking position.
Espagnolette Locking System
U PVC Casement – 3 Point Locking System Windows will use the three-point locking system known as ‘espagnolette’. This secures the sash to the frame at three points simultaneously; top, bottom, and at the handle position. This is what gives modern uPVC casement windows the weatherproofing and security advantages over single point latches.
When the handle is turned, a connecting rod runs the full height of the sash, throwing locking shoots into keeps on the frame at each point. The result is a tight, even compression of the EPDM gasket around the full perimeter — no flex between locking points.
Welded Corner Joint Strength
In uPVC window fabrication, frames and sashes are cut at 45° and welded together using heat fusion. Welded corner joint strength in properly fabricated windows means the corner is stronger than the profile itself. Poor welding — incorrect temperature, insufficient pressure, or contaminated surfaces — produces weak joints that crack visually and structurally over time.
Welded corner joint quality is visible in the neatness of the weld seam (even flash, no gaps) and can be tested by applying pressure to the corner — quality joints don’t flex.
Standard uPVC Casement Window Sizes and Glass Options
Standard casement window sizes for residential use:
- Single light: 600mm × 900mm to 900mm × 1200mm
- Double light (with mullion): 1200mm × 1200mm to 1800mm × 1500mm
- With transom: 1200mm × 1500mm to 1800mm × 2100mm
The mullion and transom uPVC members divide larger openings into individual sash units. A mullion is a vertical divider; a transom is a horizontal one. Both are structural profile members that carry the load from upper sashes to the frame.
Glazing options: Single pane (4mm or 5mm toughened), double glazed units (4mm–12mm gap–4mm), or toughened double glazed units for safety-critical locations. The casement window detail drawing from the fabricator should specify the glass type and thickness for each application.
Types of uPVC Casement Windows
Top-hung casement — hinged at the top, opens outward from the bottom. Good for ventilation with weather protection. Limited opening angle.
Side-hung casement — the standard configuration, hinged at one vertical edge. Outward opening casement window operation with friction stay hinge control.
Tilt-and-turn — dual-function sash that tilts inward from the top (ventilation) or swings inward fully (cleaning access). Common in European markets; growing in premium Indian residential projects.
Fixed light — no opening sash. Used where ventilation is provided by adjacent windows. Simpler to fabricate and more thermally efficient.
Benefits of uPVC Casement Windows
Weather performance. The espagnolette locking system and continuous EPDM gasket window seal provide better weather exclusion than most sliding window configurations.
Acoustic performance. A sealed casement with double glazing significantly reduces external noise — critical in urban locations.
Low maintenance. uPVC profiles don’t rust, rot, or require painting. Hardware should be lubricated annually.
Security. Multi-point locking at three or more points is significantly harder to force than a single-point latch.
How to Choose the Right uPVC Casement Window
Match the profile depth to the span: 60mm for standard residential windows, 70mm or 80mm for wider openings or heavier glazing.
Confirm steel reinforcement is present in all structural sections — ask for this explicitly.
Specify EPDM gaskets, not PVC.
Verify the hinge rating covers your glazing unit weight.
Use a fabricator who provides casement window detail drawing documentation and can supply the uPVC window section details for each configuration.
Duron uPVC profiles are available through trained fabricators across India, with technical support for specification and fabrication. Visit duronupvc.com or contact info@duronupvc.com for fabricator contacts and product specifications.
Conclusion
A uPVC casement window specification that covers profile depth, chamber design, wall thickness, steel reinforcement, gasket type, hardware ratings, and corner joint quality gives you a complete picture of what you’re actually installing. The details in this guide are what separate a window that performs well for decades from one that requires repair within a few years.
Window frame depth 60 mm, multi-chamber uPVC profile, EPDM sealing, and espagnolette locking are not optional upgrades — they’re the baseline for a window specification worth having.
FAQs
1. What is included in a uPVC casement window specification?
A complete uPVC casement window specification includes profile depth, chamber design, wall thickness, steel reinforcement, glazing, EPDM gaskets, hinges, and locking systems.
2. What is the standard size of a uPVC casement window?
Standard sizes range from 600 × 900 mm for single-light windows to 1800 × 2100 mm for larger configurations with transoms.
3. Why is steel reinforcement important in uPVC casement windows?
Steel reinforcement improves frame rigidity, helps resist wind loads, and prevents sash sagging, especially in casement windows wider than 900 mm.
4. Which gasket and locking system are best for uPVC casement windows?
EPDM gaskets provide durable weather sealing, while an espagnolette locking system secures the sash at multiple points for improved security.
5. How do I choose the right uPVC casement window profile?
Choose a 60 mm profile for standard residential windows and consider 70 mm or 80 mm profiles for wider openings or heavier glazing. Check reinforcement, hardware ratings, and fabrication quality.