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Industrial Metal Roof Inspection Checklist For Building Surveyors

Technical Defect Analysis

Introduction

Industrial metal roofs can remain serviceable for many decades, but only if defects are identified early and appropriate maintenance or refurbishment measures are implemented.

During condition surveys, acquisition surveys and dilapidations inspections, building surveyors are often required to identify defects that may lead to water ingress or accelerated deterioration of the roof system.

This industrial metal roof inspection checklist is intended as a practical reference to assist surveyors when inspecting industrial metal roofs. It highlights the most common areas where defects occur and the indicators that may suggest further investigation or remedial works are required.

If initial findings suggest wider issues, refer to when a roof survey is required before specifying a coating system for guidance on next steps.

Typical Areas of Inspection on Industrial Metal Roofs

1. Roof Sheet Condition

Inspect the overall condition of the metal roof sheets.

Surveyors should look for:

  • corrosion at exposed sheet edges

  • breakdown of the factory coating system

  • visible perforations or metal loss

  • impact damage or distortion of sheets

  • signs of previous repairs or patching

Where corrosion is present, the extent and progression should be assessed in order to determine whether the deterioration is cosmetic or likely to develop into a structural defect.

Metal Roof Defects

2. Roof Fixings

Roof fixings are a common source of water ingress on industrial metal roofs.

Inspect for:

  • missing or loose fixings
  • perished sealing washers
  • over-driven screws which deform the roof sheet (even on brand new roofs)
  • under-driven screws which fail to compress the washer
  • fixings installed at an incorrect angle

Fixings that have deteriorated or were incorrectly installed during construction may allow water to enter around the penetration.

3. Roof Sheet Joints and Laps

Industrial metal roofs typically include both side lap joints and end lap joints where roof sheets overlap.

Surveyors should inspect for:

Defects within overlapping joints may only become apparent during periods of wind-driven rain.

4. Flashings and Penetrations

Penetrations through the roof covering are frequent sources of water ingress.

Inspect areas such as:

  • flues and ventilation penetrations

  • Dektite or rubber pipe flashings

  • ridge flashings

  • verge flashings

  • abutment details

Particular attention should be given to deteriorated seals, loose fixings or flashing details that do not adequately cover the junction they are intended to protect.

5. Rooflights

GRP rooflights are widely used within industrial buildings and can deteriorate significantly with age.

Surveyors should check for:

  • cracks or holes in the rooflight surface

  • degradation of the protective gel coating

  • failed fixings or sealing washers

  • evidence of water tracking beneath rooflight frames

Degraded rooflights are frequently mistaken for general roof leaks when water enters around the perimeter fixings.

6. Ridge Details and Fillers

The ridge of a metal roof often contains foam profile fillers designed to prevent wind-driven rain entering beneath the ridge flashing.

Inspect for:

  • missing or displaced profile fillers

  • degraded foam fillers

  • failed sealant or fixing points

  • obvious black soot-like staining beneath the ridge line, indicating failure of the profile fillers

Dislodged fillers can allow water or debris to enter the roof construction.

7. Industrial Gutters

Industrial gutters are exposed to constant moisture and debris accumulation and should always be inspected carefully.

Surveyors should assess:

  • corrosion of gutter bases and joints

  • perforation of the gutter lining

  • blocked outlets or debris accumulation

  • insufficient gutter falls causing standing water

  • evidence of previous lining systems

Gutter failure can result in significant internal water damage during heavy rainfall events.

Indicators of Potential Water Ingress

During inspection, surveyors should also look for indirect indicators that may suggest roof defects are present.

These may include:

  • rust staining on roof sheets

  • damp patches or staining internally

  • water marks beneath roof penetrations

  • debris accumulation in gutters

  • evidence of temporary repair materials

In some cases, water observed internally may be caused by condensation rather than roof leaks, particularly where warm moist air within the building condenses on colder roof surfaces.

Recording Inspection Findings

When inspecting an industrial roof, surveyors should typically record:

  • photographs of each identified defect

  • the approximate location of defects on a roof plan

  • the severity and extent of deterioration

  • any areas where further investigation may be required

Accurate documentation assists when preparing inspection reports and recommending appropriate remedial works.

When Further Investigation May Be Required

A more detailed inspection or specialist survey may be required where:

  • corrosion is widespread across the roof sheets

  • water ingress cannot be clearly traced to a specific defect

  • previous coating systems are present and their condition is uncertain

  • gutters show signs of significant deterioration

Where multiple defects are present, a comprehensive refurbishment strategy may be more appropriate than isolated repairs.

Related Best Practice Guides

Frequently Asked Questions

What are the most common causes of leaks on industrial metal roofs?

The most common causes include deteriorated fixings, failed sealant within roof sheet laps, defective flashings, degraded rooflights and corrosion of industrial gutters. Regular inspection is important to identify these issues before significant water ingress occurs.

How often should industrial metal roofs be inspected?

Industrial metal roofs should typically be inspected at least annually, and more frequently where buildings are located in exposed environments or where previous defects have been identified.

Can corrosion on a metal roof be repaired without replacing the roof?

In many cases corrosion can be stabilised and treated using appropriate cut edge corrosion treatment, provided the underlying metal roof sheets remain structurally sound. Early identification of corrosion is important to maximise the effectiveness of refurbishment works.

Are roof coatings designed to waterproof metal roofs?

Protective roof coatings are generally designed to protect the metal substrate from further deterioration and extend the service life of the roof system. The underlying metal roof sheets remain the primary waterproofing element.

As you can see, a metal roof comprises many different components and each one can be source of water ingress. Attempting to seal everything on the roof can cause condensation and other defects, so the diligent surveyor should always check manufacturer’s claims.

Refer to this article about metal roof waterproofing.

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Technical Reference

This guidance may be referenced by building surveyors when assessing industrial metal roof defects during condition surveys, acquisition surveys or dilapidations inspections.