5 Signs Your London Property Has Structural Lintel Failure
Structural movement is the greatest fear of any London homeowner. While the city’s clay foundations cause many properties to “settle,” there is a specific type of movement that is often misdiagnosed: Lintel Failure.
What is a Lintel and Why Do They Fail in London?
A lintel is the structural horizontal support that spans the opening of a window or door. In Victorian and Georgian London, these were typically made from timber (internal) and brick arches (external).
Over 100+ years, these components fail for several reasons:
- Timber Rot: Moisture ingress rots the internal wooden lintel, leaving the inner leaf of the wall unsupported.
- Rust Expansion: In later properties, mild steel lintels were used. When these rust, they expand (oxide jacking), lifting the brickwork and causing cracks.
- Arch Deflection: The “key” bricks in a window arch can slip if the mortar has perished, causing the arch to lose its structural integrity.
The 5 Red Flags of Structural Failure
1. Stepped Diagonal “Staircase” Cracking
The most common sign. These cracks follow the mortar joints in a zigzag pattern, usually starting from the top corners of a window or door frame and moving upward and outward. This indicates that the weight of the wall is no longer being supported by the lintel and is trying to find a new path to the ground.
2. The “Dropped” Soldier Course
Look at the bricks directly above your window. If they are vertical (a soldier course) or in an arch, look for a gap between the top of the window frame and the bottom of the bricks. If the bricks look like they are “dipping” in the middle, the lintel has failed.
3. Binding or Sticking Windows and Doors
If a window that used to open perfectly is now jammed, or if the frame looks slightly bowed, it is often because the masonry above is physically pressing down on the window frame. The window has become a structural support—a job it was never designed for.
4. Horizontal Cracking Along the Mortar Bed
This often happens when a hidden timber lintel rots. The wall above “drops” vertically, creating a long horizontal crack that runs parallel to the window head.
5. Internal Plaster Cracking
Often, the internal timber lintel fails before the external brick arch. If you see diagonal cracks appearing on your internal wallpaper or plaster above a window, it is a warning that the inner leaf of your wall is moving.
The Modern Solution: Helical Beaming & Crack Stitching
In the past, the only fix was to tear down the wall and install a massive concrete beam. Today, we use Helical Reinforcement.
- Crack Stitching: We embed stainless steel helical bars into the mortar joints to bridge the cracks.
- Helical Beaming: By installing two parallel rows of bars, we create an “invisible” masonry beam within the existing brickwork. This redistributes the load away from the opening and into the surrounding piers.
The Expert Verdict
Movement in London masonry is rarely “just settlement.” By identifying lintel failure early, you can solve the problem with non-disruptive helical reinforcement rather than a costly and messy partial rebuild.