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Understanding Metal Roof Fixing Defects

Industrial Roof Technical Defects Analysis

What This Defect Is

There are numerous defects that can affect fixings on metal roofs and it is common during roof surveys, to find corroded fixing heads, misaligned and unwinding fixings. All of these defects can be a sign that something else is wrong with the roof, though in most cases, fixing defects are isolated in nature.

Causes

  • Loss of protective fixing caps
  • Neglect and lack of a roof maintenance programme

How to Identify

A visual inspection of the roof surface will soon identify fixing issues, so the inspection needs to be methodical and all areas of the roof need to be trafficked. It can be difficult to identify fixing issues by using a drone or other remote access method.

  • Misaligned fixings
  • Unwinding fixings
  • Missing fixings
  • Over-tightened fixings

Risks if Untreated

  • Progressive corrosion of the fixings, extending down the shank and causing structural failure of the fixing
  • Misaligned fixings can be a source of water ingress
  • Wind-uplift vulnerabilities due to weakened fixings
  • Over-tightened fixings are identified easily because the roof sheet will be dented and it’s likely that the EPDM seal will be broken or lifted.
  • Missing fixings are a source of water ingress

Metal Roof Defects

Metal Roof Defects

​Condition Ratings

Early

Isolated defects noted during a roof inspection – misalignment, unwinding, etc.

Moderate

Missing fixing caps throughout. Light corrosion noted to fixing heads. Rust staining. Misaligned or unwinding fixings noted in several locations.

Poor

Extensive rust present to fixings throughout, with staining apparent on the roof sheets.

Severe

Extensive corrosion throughout at the fixing points. Missing, unwinding or misaligned fixings throughout. Perforations evident to roof sheets around fixing positions.

Image showing pressure testing of fixings on metal roofs and cladding

Image shows pressure test being conducted on a fixing.

Randomised testing of fixings doesn’t guarantee that all fixings are correctly installed or in good condition, but it can help identify isolated water ingress points in a given area.

Recommended Treatment

We recommend that defective fixings are replaced wherever possible. The new fixings include an EPDM seal to provide protection against water ingress.

If replacement is not practicable, as part of a roof coating project or as a stand-alone repair, we have a product called Non-Sag Sealer that will retrospectively seal defective fixings, but note that a coating repair is not structural, so loose fixings need to be tightened.

  • Mechanically prepare the fixing, removing heavy corrosion
  • Prime fixing with Liquasil SWT Corrosion Primer.
  • Once dry, apply Liquasil Non-Sag Sealer to and around the fixing

Specification Wording

“Remove heavy corrosion using wire brush or similar. Apply a thin coat of Liquasl SWT Primer to each fixing and allow to dry. Apply a liberal coat of Liquasil Non-Sag Sealer to and around the fixing, ensuring that it is fully encapsulated”

Additional Options

  • Replace defective fixings with oversized fixings.

Suitable Liquasil Products

  • Liquasil SWT Primer
  • Liquasil Non-Sag Sealer

Best Practice Guides

Best Practice Guides