uPVC on its own is not stiff enough to resist wind load on large windows, and it expands with heat. Galvanised steel reinforcement inside the profile chamber gives the frame its strength, holds hardware screws, and keeps sashes square.
Where reinforcement is needed
- Outer frames, especially on wide or tall windows
- Sashes carrying hinges and locks
- Mullions and transoms, which carry the most wind load
- Door frames and door sashes
Choosing the section
| Section | Typical use | Stiffness |
|---|---|---|
| U-channel | Frames, sashes | Good |
| C-channel (lipped) | Door and large sashes | Better |
| Square / box | Mullions, couplers | Highest |
| Custom | Specific profile chambers | As designed |
Thickness
Reinforcement commonly ranges from about 1.0 mm to 2.0 mm. Thicker steel is needed for larger windows, doors, high-rise buildings and high wind zones. The profile system supplier's guidelines and the window's span decide the minimum.
Zinc coating (GSM)
Reinforcement sits inside a closed chamber but can still see condensation. A specified zinc coating protects against corrosion that would otherwise stain and weaken the frame. Always state the coating requirement when ordering.
How to order
Send us your profile drawing or a sample, the section type, thickness, coating, lengths and monthly volume. We roll-form to your chamber dimensions and supply in standard or cut lengths.