EPDM Gaskets in Facade and Fenestration Systems

What it is

Ethylene propylene diene monomer rubber, extruded into profiles that seal glass to frame and frame to frame. It is the sealing element in almost every engineered aluminium fenestration and curtain wall system.

Small item, disproportionate consequence.

Specification at a glance

Property	Typical specification
Material	EPDM, dense or sponge by function
Hardness	60 — 70 Shore A typical for glazing
Classification	ASTM D2000 line call-out
Corners	Vulcanised, not cut and butted
Colour	Black standard; grey and white available
Service life	Decades under UV without embrittlement

Why it outlasts the alternatives

EPDM's polymer backbone has no unsaturated bonds in the main chain, which is the technical reason it resists ozone and UV attack where other elastomers harden. In practical terms: an EPDM gasket on a west elevation in Delhi is still compressible after twenty summers. A PVC gasket in the same position is often hard and shrunken within five.

A hardened gasket does not seal. Water then enters the glazing rebate, attacks the DGU secondary seal, and the unit fogs.

Where it sits in the system

Location	Function
Glazing rebate, inner and outer	Seals glass to frame, allows movement
Frame to frame joints	Seals the assembly line
Drainage path	Shaped to keep the rebate drained, not dammed
Compression seal on openable sashes	Air and water tightness when closed

Where projects go wrong

• Cut and butted corners on a system that was tested with vulcanised ones.
• Gasket substitution at supply stage, voiding the tested performance.
• Over-compression, which takes a permanent set and leaves the seal slack.
• Stretching gaskets during installation. A stretched gasket recovers over months and pulls back from the corners, opening a gap at exactly the point water collects.
• Blocked drainage. A gasket seated wrongly can dam the rebate instead of draining it.

Standards referenced

Rubber material classification under ASTM D2000. Assembly air leakage to ASTM E283 and water penetration to ASTM E331, both of which are tested with the specified gasket in place.