10 Problems Caused by Poorly Installed Lead Flashing

Introduction

Lead flashing plays a vital role in weatherproofing a roof. Found around chimneys, valleys, roof joints and abutments, it prevents water from seeping into areas where different building materials meet. However, when flashing is installed incorrectly—be it rushed, poorly fitted, or without the right expansion gaps—it can quickly become a weak point rather than a protective barrier.

At WBN Roofing Rossington, we’ve repaired numerous roofing issues caused by bad flashing work across Rossington and surrounding areas in South Yorkshire. Below, we highlight ten of the most common problems that arise from poorly installed lead flashing—problems that can be both frustrating and costly if left unchecked.

1. Water Leaks Around Chimneys and Valleys

Improperly sealed or inadequately lapped flashing allows rainwater to bypass the barrier and seep directly into your roof structure. Chimneys are particularly vulnerable, as water runs directly toward these junctions during rainfall.

2. Damp and Mould on Interior Walls

Once water enters the property, it doesn’t take long for internal walls and ceilings to show signs of damp. This often results in discolouration, peeling paint, mould growth, and musty odours—especially in loft conversions or upper rooms.

3. Timber Rot in Roof Structures

Persistent moisture from leaking flashing leads to rot in key timber components of your roof. Rafters, joists, and battens can degrade over time, compromising structural stability and requiring extensive remedial work.

4. Sagging or Collapsing Rooflines

Over time, untreated water ingress softens the timber supports beneath the roof covering. In worst cases, this leads to noticeable sagging or partial collapse, which poses both safety and financial risks.

5. Damage to Loft Insulation

When flashing fails, water can soak into loft insulation, reducing its effectiveness and leading to heat loss. Damp insulation may also need to be replaced entirely if mould sets in.

6. Cracking in Lead Due to Movement

If the flashing hasn’t been installed with the correct expansion allowances, the lead may crack as it expands and contracts with temperature changes. These cracks create access points for water and accelerate deterioration.

7. Unsightly Staining on Exterior Brickwork

Water that leaks behind flashing often tracks down external walls, causing efflorescence or staining. These marks not only affect the property’s appearance but can be an early warning of more serious underlying issues.

8. Increased Risk During Frost or Heavy Rain

Inadequate flashing becomes particularly problematic in severe weather. During freeze-thaw cycles, trapped water expands and worsens cracks, while heavy rain accelerates the rate of infiltration and internal damage.

9. High Repair Costs from Escalating Damage

A small flashing issue left unresolved can lead to widespread repair needs—from internal redecoration to full roof timber replacement. The longer the problem goes undetected, the more expensive it becomes to fix.

10. Reduced Property Value and Saleability

Visible roof issues or internal signs of water damage caused by poor flashing deter potential buyers and lower your property’s value. A professional roof inspection will quickly pick up signs of poor workmanship—leading to a loss of confidence from would-be buyers.

Conclusion

Lead flashing may seem like a minor detail, but when it’s installed poorly, it becomes a major liability. The problems it causes are not just superficial—they affect the structural integrity, thermal performance, and overall value of your home.

At WBN Roofing Rossington, we deliver precise, professional flashing installation and repairs that stand the test of time. If you’re noticing signs of water ingress or suspect flashing may be the culprit, get in touch today. A well-installed roof is more than protection—it’s a smart, long-term investment in your property’s future.

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