A Hidden Problem Causing Serious Damage

In recent years, metal coil stock lintels are a concerning issue that has begun to emerge in homes following window replacements — and most homeowners have no idea it’s happening until the damage is already done.

The problem involves metal coil stock being wrapped around steel lintels above windows. While this may look neat and modern from the outside, it can quietly create the perfect conditions for structural failure.

If left unchecked, it can lead to rusting steel, expanding metal, and cracked brickwork above your windows — a problem known as lintel failure.

What Is a Lintel — and Why Does It Matter?

It is a critical structural component.

If it fails, the consequences are not cosmetic — they are structural.

What Is Metal Coil Stock — and Why Is It Used in lintels?

Metal coil stock is a thin aluminium or coated metal sheet often used by contractors during window lintels installations. It is bent and shaped to create a clean, maintenance-free finish around window frames.

On the surface, this seems like a good idea:

It improves appearance
It reduces visible gaps
It protects exposed areas

However, problems arise when this material is installed incorrectly — particularly when it is wrapped over the lintels.

The Core Problem: Trapped Moisture

The issue is not the metal itself — it is how it interacts with the structure behind it.

When coil stock is wrapped tightly over brick lintels, it can:

Seal the area too effectively
Block natural drainage and ventilation
Trap water between the metal and the brick/steel

Rainwater, condensation, and moisture have nowhere to go.

Instead of drying out naturally, the area remains damp — sometimes permanently.

What Happens Next: Rust, Expansion, and Cracking

Lintels are structural supports placed above windows and doors. In most brick homes, this is typically a steel lintel designed to carry the weight of the brickwork above the opening.

Steel and moisture are a dangerous combination.

When the steel lintel is exposed to prolonged damp conditions:

Rust begins to form
Rust causes the steel to expand
The expanding metal pushes against surrounding brickwork

This creates pressure from within the structure.

The result is often very visible:

Horizontal cracks above windows
Stepped cracking in brick mortar joints
Bulging or lifting brickwork

This is classic lintel failure — and once it starts, it does not fix itself.

Why This Problem Is Increasing

This issue is becoming more common due to modern installation practices.

Many window installers:

Focus on speed and appearance
Use coil stock as a quick finishing solution
May not fully consider long-term moisture behaviour

In some cases, proper cavity trays or drainage paths are ignored or compromised during installation.

The result is a system that looks neat on day one — but quietly deteriorates over time.

The Real Danger: It’s Hidden Until It’s Serious

One of the biggest problems with this issue is that it develops out of sight.

From the outside, everything may look fine initially.

By the time you notice:

Cracks above windows
Staining or rust marks
Movement in brickwork

…the damage is already well underway.

And because the coil stock covers the area, it can hide the early warning signs.

How to Spot the Warning Signs

If your windows have been replaced in recent years, especially with metal capping or trim, look out for:

Horizontal cracks directly above window frames
Rust staining on brickwork
Slight bulging or uneven brick lines
Gaps forming between bricks or mortar

Inside the property, you might also notice:

Cracks in plaster above windows
Difficulty opening or closing windows (in severe cases)

These are all indicators that the lintel may be under stress.

Can It Be Fixed?

Yes — but the solution depends on how advanced the problem is.

Early Stage:

Removal of coil stock
Inspection of lintel condition
Improving drainage and ventilation

Moderate Damage:

Partial repair or treatment of the lintel
Repointing brickwork

Severe Cases:

Full lintel replacement
Rebuilding affected brickwork

As with most structural issues, early intervention is far cheaper and simpler.

How to Avoid the Problem

If you are planning new windows or external work, this is where you can make better decisions.

Key Advice:

Avoid wrapping coil stock directly over lintels
Ensure proper drainage paths are maintained
Use breathable construction methods
Ask installers specifically about lintel detailing

A good contractor should understand moisture management — not just appearance.

A Better Approach

Instead of sealing everything tightly, a well-designed system should:

Allow water to escape
Allow air to circulate
Protect structural elements without trapping moisture

In traditional construction, this balance was well understood.

Modern shortcuts sometimes ignore it — and that’s where problems begin.

The Bottom Line

Metal coil stock around brick lintels may look clean and professional, but when installed incorrectly, it can create a hidden and serious structural risk.

The key issue is simple:

Trapped moisture leads to rust — and rust leads to expansion, cracking, and failure.

For homeowners, the implications are clear:

Structural damage above windows
Expensive repairs if left unchecked
Reduced property integrity

For DIY enthusiasts and renovators, the lesson is even clearer:

Never sacrifice long-term durability for short-term appearance.

If your home has had recent window work, it’s worth taking a closer look.

Because with this issue, what you can’t see…

…is exactly where the problem begins.