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uPVC Steel Reinforcement Sections: Types, Gauges, Coatings and Compatibility
uPVC steel reinforcement is a cold roll-formed, galvanised steel section inserted into the hollow chamber of a uPVC window or door profile to give the frame the stiffness uPVC does not have on its own. Aparna Rollform manufactures six reinforcement shapes — C, box, step, open lip, OSLC and groove channels — in 0.8–3.0 mm thickness, 3–6 m lengths and 80 or 120 GSM zinc coating.
Sections are roll-formed at our plant near Patancheru, on the outskirts of Hyderabad, and supplied to uPVC window fabricators and profile companies across India.
uPVC reinforcement is a formed sheet-steel section. It is not the same product as reinforcement bars (rebar) used in concrete.
uPVC Steel Reinforcement Specifications
Aparna Rollform uPVC reinforcement is supplied in 0.8 mm to 3.0 mm thickness and 3.0 m to 6.0 m lengths, roll-formed from galvanised (GI) steel sheet with 80 GSM or 120 GSM zinc coating. Width and height are formed to match the reinforcement chamber of the uPVC profile system.
| Parameter | Aparna Rollform supply range |
|---|---|
| Sections | C channel, box, step channel, open lip channel, OSLC, groove channel |
| Material | Galvanised (GI) steel sheet |
| Thickness | 0.8 mm – 3.0 mm |
| Length | 3.0 m – 6.0 m |
| Width and height | Formed to suit the uPVC profile chamber |
| Zinc coating | 80 GSM or 120 GSM |
| Process | Cold roll forming |
Reinforcing a new profile system? Send us the profile drawing and we will confirm the matching section.
Types Of UPVC Steel Reinforcements
The section shape is set by the uPVC profile, not the other way round. Each profile system has a reinforcement chamber of a specific shape, and the steel must slide into it with little play and sit against the walls that hinge and lock screws pass through. For the same thickness, a closed section resists twisting far better than an open one; lips and steps add stiffness to open sections.
Shape: an open channel with a lip or flange on its side(s), formed to the geometry the profile system specifies.
Character: an open section stiffened by its lips.
Chosen when: the profile system’s drawing calls for an OSLC section.
Shape: a U or C channel with lips turned in along both open edges.
Character: the lips stiffen the free edges, so it is stiffer than a plain C channel of the same thickness while remaining an open section.
Chosen when: the profile chamber is designed for a lipped channel.
Shape: a closed rectangular tube.
Character: the highest resistance to bending and twisting of the six shapes for similar outer dimensions and thickness.
Chosen when: the profile has a rectangular chamber and the member carries higher loads, such as large frames, mullions and door members.
Shape: a channel with a stepped, offset cross-section.
Character: the step lets the steel follow a non-rectangular chamber and adds stiffness to the section.
Chosen when: the profile’s reinforcement chamber is stepped
Shape: an open, three-sided C section.
Character: light and quick to insert; of the six shapes, it offers the least resistance to twisting.
Chosen when: the profile has a C-shaped reinforcement chamber, often used in sashes and smaller frames.
Shape: a channel with a groove running along its length.
Character: the groove follows a matching detail inside the profile chamber and stiffens the section.
Chosen when: the profile chamber includes that groove detail.
Why uPVC Windows and Doors Need Steel Reinforcement?
Steel is roughly 70 to 80 times stiffer than uPVC (elastic modulus of about 200 GPa against about 2.5–3 GPa), and uPVC loses more stiffness as it heats in direct sun. Without reinforcement, a uPVC frame can bow under wind pressure, sag under glass weight and lose its grip on hinge and lock screws. The steel core carries these loads while the uPVC provides the weather seal, finish and insulation.
- Wind-load resistance: keeps frames and sashes from deflecting under wind pressure, which matters most on tall buildings and exposed sites.
- Secure hardware fixing: hinge, lock and handle screws pass through the uPVC wall and bite into steel instead of plastic alone.
- Straight, square sashes: holds members straight so seals compress evenly and windows keep opening smoothly over years of use.
- Larger openings: allows bigger and taller window and door units, within the limits the profile system sets.
- Security: a stiffer frame is harder to lever or flex at the lock points.
- Corrosion protection: the zinc coating protects the steel inside the profile chamber.
Disclaimer: The engineering metrics cited are industry averages. Actual material thresholds and reinforcement requirements vary based on manufacturing tolerances, window dimensions, and local building codes. This information is for educational purposes and does not replace certified structural calculations.
How to Choose uPVC Reinforcement?
Choose uPVC reinforcement in this order: match the section to the profile chamber, take the thickness from the profile system’s reinforcement tables for the member size and design wind pressure, choose the zinc coating for the site environment, then set lengths to suit your cutting plan.
- Profile system and chamber: the profile supplier’s drawing fixes the section shape and outer dimensions. A loose section gives poor screw grip; a tight one will not insert.
- Member size and wind pressure: whether a member needs steel, and how thick, comes from the profile system’s reinforcement (static) tables, based on member length and the design wind pressure for the site. In India, design wind pressure is worked out under IS 875 (Part 3). Taller buildings and coastal or exposed sites face higher pressure. [1]
- Glass weight and hardware: heavy double-glazed units, large sliding sashes and multi-point locks add load to the members that carry them.
- Environment and coating: the heavier 120 GSM coating suits coastal, high-humidity and industrial sites (see the next section).
- Length and wastage: reinforcement is supplied in 3–6 m lengths, so order lengths that fit your frame cutting plan to reduce offcuts.
GI Reinforcement: 80 GSM vs 120 GSM Zinc Coating
GI reinforcement is uPVC reinforcement roll-formed from galvanised iron, meaning zinc-coated steel sheet. The GSM figure is the zinc coating mass in grams per square metre, normally counted across both faces of the sheet, so a 120 GSM coating carries 50% more zinc than an 80 GSM coating.
Zinc protects steel in two ways. It acts as a barrier, and at cut edges and screw holes it corrodes in preference to the exposed steel. Reinforcement is enclosed in the profile, but it is cut, drilled and screwed during fabrication, which is why coating mass still matters.
| Coating | Zinc mass | Typically specified for |
|---|---|---|
| 80 GSM | 80 g/m² | Standard inland residential and commercial projects |
| 120 GSM | 120 g/m² (50% more zinc than 80 GSM) | Coastal, high-humidity and industrial sites, or wherever the project specification calls for a heavier coating |
Where uPVC Reinforcement Is Used?
Reinforcement goes into the load-carrying members of uPVC windows and doors. The profile system’s fabrication manual states which members must be reinforced and with which section.
| Member | What the reinforcement does |
|---|---|
| Outer frame | Keeps the frame straight between fixings and gives hinges and lock keeps a steel fixing |
| Sash or door leaf | Holds the sash square under glass weight and carries hinge, handle and lock screws |
| Mullion and transom | Stops long intermediate members from bowing under wind load |
| Sliding sash and interlock | Stiffens the meeting members of sliding windows and doors |
| Door frame | Carries the weight and repeated use of door leaves and multi-point locks |
It is used across casement, sliding, tilt-and-turn and fixed windows, and in sliding, French and entrance doors, for residential, commercial and institutional projects.
uPVC Reinforcement Manufacturer and Supplier for Fabricators
To quote accurately, we need six details from you:
- Profile system name, or the reinforcement chamber drawing
- Section type (C, box, step, open lip, OSLC or groove)
- Thickness (0.8–3.0 mm)
- Length (3.0–6.0 m)
- Zinc coating (80 or 120 GSM)
- Quantity and delivery location
Reinforcement is quoted per enquiry because price depends on thickness, coating, section shape, length and order quantity, and follows steel coil prices. Every section is cold roll-formed from galvanised coil in a continuous process, which produces a consistent cross-section along the full length.
About Aparna Rollform
Aparna Rollform is the roll-forming division of Aparna Enterprises Limited, a Hyderabad building-materials group founded in 1990. From its plant near Patancheru, it manufactures uPVC steel reinforcement, and its range also includes cable. The division holds ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certification.
Frequently Asked Questions On uPVC Steel Reinforcement
What is uPVC steel reinforcement?
uPVC steel reinforcement is a cold roll-formed, galvanised steel section inserted into the hollow chamber of a uPVC window or door profile to give the frame the stiffness uPVC does not have on its own. It carries wind load, glass weight and hardware screws, while the uPVC provides the seal, finish and insulation.
Do all uPVC windows need steel reinforcement?
Not every member of every window, but most frames and sashes do. The profile system’s fabrication rules state which members must be reinforced, based on member length, profile colour, glass weight and design wind pressure. Hinge and lock positions are normally reinforced so their screws fix into steel.
What thickness of steel is used in uPVC reinforcement?
Aparna Rollform supplies uPVC reinforcement from 0.8 mm to 3.0 mm thick. The right thickness for a project comes from the profile system’s reinforcement tables for the member length and design wind pressure, not from a single standard value.
What is GI reinforcement for uPVC windows?
GI reinforcement is uPVC reinforcement roll-formed from galvanised iron, meaning zinc-coated steel sheet. Aparna Rollform supplies it with 80 GSM or 120 GSM zinc coating.
What is the difference between 80 GSM and 120 GSM reinforcement?
The GSM figure is the zinc coating mass in grams per square metre, normally counted across both faces of the sheet, so a 120 GSM coating carries 50% more zinc than an 80 GSM coating. The heavier coating is typically specified for coastal, high-humidity and industrial sites.
Which reinforcement shape should I use?
Use the shape that matches the reinforcement chamber of your uPVC profile system, as shown on the profile supplier’s drawing. For the same thickness, a closed box section resists twisting far better than an open C channel.
Does steel reinforcement affect the thermal insulation of uPVC windows?
Steel conducts heat far better than uPVC, so reinforcement does carry some heat through the frame. Profile systems limit this by placing the steel in an inner chamber, separated from the outer faces by insulating air chambers. When comparing frame U-values, ask the profile supplier whether the stated value includes reinforcement.
What lengths is uPVC reinforcement supplied in?
Aparna Rollform supplies uPVC reinforcement in lengths from 3.0 m to 6.0 m. Choose lengths that suit your frame cutting plan to reduce offcuts.
How is uPVC steel reinforcement priced?
Reinforcement is quoted per enquiry because price depends on thickness, coating, section shape, length and order quantity, and follows steel coil prices. Share your profile system, section, thickness, length, coating, quantity and delivery location for a quote.
Request a Quote for uPVC Steel Reinforcement
Share your profile system or chamber drawing, section type, thickness, length, zinc coating and quantity, and our team will confirm the matching section and send a quotation.
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