Profiled Foam Closures in Metal Roofing: Why Avoid at Eaves

Source

Key lesson

Using profiled foam closures under metal roof sheets at the eaves to block wind-driven rain is not recommended and often prohibited. They restrict ventilation, causing moisture build-up, mould, corrosion and early roof failure.

Official Guidance

• NZMRM Code of Practice
  Use only where required for weathertightness (e.g. around windows) or controlled internal pressure.

  “As they restrict the free movement of air, their use should be restricted… Profiled closures should be of closed cell type.”

• E2/AS1

  8.4.15 “Preformed compressible seals shall not be used at the eaves.”

Types

• Narrow tipped – fits under profile
• Wide tipped – fits over profile

Main Problems

• Blocks ventilation → excessive internal moisture
  • Mould growth (dwellings)
  • Corrosion of sheets & purlins
  • Longer “time of wetness” → premature failure (seen after ~14 years)
  • Poor dissipation of vehicle emissions (freight depots)
• Practical issues
  • Often fall into gutters, blocking water flow
  • Degrade from heat & reflected UV after a few years

Better Options

• Remove the foam where not essential for weathertightness
• Vermin control at eaves → use an eaves comb (durable, allows airflow)

When Acceptable

• Window jamb flashings / scribers
• Atmosphere-controlled buildings

Source

NZMRM Bulletin BPC01 – Profiled Foam Closures
Author: Rod Newbold, Technical Consultant
Website: www.metalroofing.org.nz/bulletins

Takeaway: Prioritise ventilation over foam fillers at eaves to prevent long-term damage.