Supporting the Dream: The Engineering Behind Bi-Fold Doors
Bi-Fold Doors and Steel Frames: Creating the ‘Inside-Outside’ Look
The trend for massive spans of glass—bi-fold or sliding doors—at the rear of a property shows no sign of slowing down. But glass cannot support the weight of the house above it.
The Challenge: The Missing Wall
When a solid masonry rear wall is replaced with glass, the structure’s stiffness is removed. Without proper engineering, the house could technically “rack” (twist) in high winds, or the brickwork above could sag, crushing the door frames and shattering the glass.
The Solution: The Portal Frame
For wide openings, a simple lintel often isn’t enough. Engineers typically design a Steel Portal Frame. This looks like a goalpost: two steel columns bolted to a top beam.
- This frame provides rigid stability, replacing the structural stability of the original wall.
- It transfers the load down to the foundations.
Wind Posts
If an extension is particularly tall or exposed to high winds, engineers may also specify wind posts—steel reinforcements hidden within the walls to help resist masonry deflection under wind pressure.
Disclaimer: The information provided in these articles is for general interest and educational purposes only and does not constitute professional structural engineering advice. Every project is unique. You should always consult a qualified Structural Engineer for site-specific advice before undertaking any construction work.
