Commercial Metal Roof Defects

Common Defects in Commercial Metal Roofing

Cut-Edge Corrosion on Profiled Steel Sheets

Cut-edge corrosion is a common concern with coated profiled steel roofing. It often affects sheet ends, eaves and overlaps.

Manufacturers protect profiled steel sheets with metallic and organic coatings. However, exposed edges can become vulnerable to corrosion, particularly where moisture remains in contact with the material.

Early warning signs include rust staining, peeling coatings and visible deterioration along the sheet edges.

Over time, corrosion may progress beyond the protective coating and affect the underlying steel. The extent of this damage helps determine whether local treatment remains a suitable option.

Protective coatings may help where the underlying steel remains sufficiently sound. However, coating alone cannot resolve advanced corrosion or restore strength to badly deteriorated sheets.

Before recommending treatment, contractors should consider the original roofing material, protective finish and manufacturer’s guidance.

Tata Steel’s guidance for coated steel products provides useful technical information about construction detailing, cut edges and long-term performance.

Leaking Gutters and Rainwater Drainage

Gutter defects frequently affect commercial and industrial buildings, particularly where the roofing system has experienced years of exposure.

Leaks near roof edges or valley gutters may result from corrosion, damaged joints or deteriorating seals. Blocked outlets and restricted drainage can also allow water to accumulate. Standing water may expose existing weaknesses and increase the risk of further deterioration.

Importantly, an internal water stain does not always reveal the exact point where water enters the building.

Water can travel along roofing components or structural elements before appearing inside. Consequently, repairing the area directly above a stain may not resolve the original leak.

A thorough investigation should consider the gutters, drainage outlets, adjoining roof sheets and surrounding junctions together.

Deteriorating Fixings, Laps and Roof Details

A commercial metal roof depends on more than the condition of its external sheets. Fixings, sealing washers, roof-sheet overlaps, flashings and penetrations all help protect the building against water ingress.

Over time, individual components can deteriorate or lose their effectiveness. Corroded fixings, damaged seals and defective flashings may allow water to enter even when the main roof sheets remain sound.

These areas require particular attention when leaks return after previous repairs. They also deserve investigation when staining appears near roof junctions or penetrations.

What Should a Commercial Roof Inspection Establish?

A commercial roof inspection should identify more than the visible symptoms of deterioration.

It should help establish the likely causes, extent and implications of the defects. This information can then guide decisions about further investigations and suitable remedial works.

Depending on the building and its roofing system, an inspection may consider:

• The roof’s age, construction and general condition.
• The extent of corrosion, coating damage or deteriorating sheets.
• The condition of gutters, outlets, fixings, laps and flashings.
• Visible evidence of water ingress and previous leaks.
• The condition of accessible rooflights and vulnerable details.
• Previous repairs, alterations or maintenance work.
• Whether further specialist investigation is necessary.

Operation and maintenance (O&M) manuals can provide valuable information about the original roofing system. These documents may identify the materials, construction details and recommended maintenance arrangements.

However, the original records may not reflect the roof’s current condition. Later alterations, previous repairs and years of exposure can all affect its performance.

Surveyors should therefore consider the available documentation alongside the roof’s present condition.

When Is Opening Up the Roof Necessary?

Not every commercial roofing problem requires intrusive investigation.

In some cases, a competent inspection can establish the cause and extent of visible defects. This may provide enough information to develop an appropriate repair specification.

However, the external condition does not always reveal what is happening beneath the roof covering.

For example, a building surveyor may need to confirm the original construction details. They may also need to investigate concealed deterioration or check whether water has affected underlying materials.

In these circumstances, the surveyor may recommend carefully planned opening-up works.

The investigation should have a clearly defined purpose. Those responsible must also consider safe access, weather protection and the reinstatement of affected areas.

Before work begins, the parties should agree who will manage each stage. This includes any specialist assessment, temporary protection and final weatherproofing.

The aim is to obtain reliable information without causing unnecessary damage or introducing additional risks.

Choosing the Appropriate Remedial Works

Once an investigation establishes the condition of the roof, the building owner can consider the available remedial options.

The most suitable approach depends on the cause, extent and severity of the defects. The remaining condition of the roofing system also plays an important role.

Localised Roof Repairs

Targeted repairs may offer a practical solution where damage affects only a limited area.

For example, contractors may replace individual damaged sheets, repair defective details or renew deteriorating fixings. They may also address leaking gutter components or failed seals.

The proposed repairs should tackle the underlying cause rather than simply conceal the visible damage.

Metal Roof Refurbishment and Protective Treatments

Refurbishment may provide an alternative to replacement when the existing roof remains suitable for continued use.

Depending on the condition of the roofing system, suitable works might include surface preparation, corrosion treatment or protective coating applications.

However, not every roof will benefit from the same approach.

The contractor must consider the severity of corrosion, the condition of the underlying steel and the compatibility of proposed materials. Manufacturer requirements may also influence the specification.

A suitable refurbishment programme should address the identified defects and support the roof’s continued performance.

Partial or Complete Roof Replacement

Some roofing systems eventually reach a point where repairs or refurbishment no longer offer a practical solution.

Extensive corrosion, weakened sheets and repeated water ingress can all influence the decision to replace a roof.

Building owners should consider the roof’s overall condition, the likely performance of repairs and the expected costs over time.

They should also assess how the work might affect the building’s occupants and daily operations.

A cheaper initial repair does not always provide better long-term value, particularly when defects continue to recur.

JTC Roofing & Cladding provides a range of roofing and cladding repairs and restoration services for commercial and industrial buildings.

Planning Roof Investigations Safely

Commercial roof investigations require careful planning, particularly when the building has an ageing or unfamiliar roofing system.

Corroded metal sheets, rooflights and other roofing components can create serious fall risks.

Contractors should never assume a roof is safe to walk on simply because someone has accessed it before.

The Health and Safety Executive’s guidance on roof work explains the importance of competent workers, suitable access arrangements and precautions against falls.

Those arranging an inspection must consider these risks before work begins. They should also plan any subsequent repairs with the building’s occupants and operations in mind.

This is particularly important for factories, warehouses, hospitals and other buildings that remain operational during roofing work.

Preparing a Commercial Roofing Enquiry

Clear information helps roofing contractors understand the nature of a problem and the potential scope of work.

When requesting advice or a quotation, building owners and surveyors should provide as much relevant information as possible.

Useful details may include:

• The building’s location and approximate age.
• The type of roof covering and its known construction.
• Any available O&M manuals or previous inspection reports.
• The location and nature of visible defects.
• Details of recurring leaks or previous repairs.
• Photographs taken safely from accessible locations.
• Access restrictions or operational requirements.
• Any important project deadlines or budget considerations.

If a building surveyor has already identified roofing defects, their findings can provide a useful starting point.

These details help establish whether the proposed works require further investigation before a contractor can prepare an accurate quotation.

Discuss Your Commercial Roofing Requirements

JTC Roofing & Cladding Ltd provides industrial and commercial roofing services across Hertfordshire, Cambridgeshire and the wider UK.

Our work includes roof repairs, refurbishment and replacement for commercial and industrial buildings.

Whether you manage an ageing industrial roof or need to address recurring leaks, our team can discuss your roofing requirements and the available options.

Explore our industrial and commercial roofing services or contact JTC Roofing & Cladding to discuss your project.