EPDM gaskets: the rubber seals that keep windows tight

Look closely at any aluminium or uPVC window and you will see a black rubber strip where the glass meets the frame, and another where the sash closes against it. Those are gaskets, and the best of them are EPDM. In the dust and heat of Gurugram and Noida, the gasket is often the part that decides whether a window stays quiet and dry or starts letting in fine dust, rain and noise.

What is EPDM and why is it used for seals?

EPDM (ethylene propylene diene monomer) is a synthetic rubber. Its backbone has no double bonds exposed in the main chain, which is why it shrugs off ozone and UV that make many other rubbers crack. It is typically rated for continuous service from about −40°C up to well over 100°C, comfortably beyond the surface temperature of a dark window frame in a Delhi summer. It stays springy, so it keeps pressing against glass and frame year after year.

Where are EPDM gaskets used?

• Glazing gaskets: the wedge or bulb seals that hold the glass in aluminium sections and uPVC profiles.
• Weather seals: the strips a casement sash or slide and fold door closes against.
• Facade systems: pressure plates and gaskets in curtain walls, alongside structural silicone on structural glazing.
• Glass railings and shower seals: some base channels and seal strips use EPDM or similar rubbers to cushion glass.

Sliding windows usually rely more on brush (wool pile) seals in the interlock, with EPDM around the glass. Casement windows, which compress a gasket all round, usually seal tighter, a point covered in our sliding vs casement windows guide.

How do you tell a gasket has failed?

• Gaps at the corners where the strip has shrunk back.
• Rubber that feels hard and plasticky or shows surface cracks.
• Fine dust lines on the inside sill after a dust storm, or water at the bottom corner during rain.
• Whistling in high wind, covered on window whistling in wind.
• Rattling glass in the frame.

How do you check gasket quality?

When buying windows, ask what the gasket material is. EPDM gaskets are typically matt black, springy and do not feel waxy; cheap PVC strips often feel stiffer and may be shinier. Check that corners are properly joined or moulded rather than butted with a gap, and that the seal is continuous around the sash. A torch held outside a closed window at night shows light leaks clearly.

Common confusions

EPDM is sometimes mixed up with silicone sealant. Gaskets are pre-formed strips that are pushed into a groove and can be replaced; silicone is a gun-applied paste that cures in place and bonds. Weep holes are different again: they let water that does get past the seal drain out. A leaking window can be any of the three, as our window leaking rain water page explains.

Care and replacement

1. Clean gaskets with water and mild soap; avoid petrol, thinner or oily sprays, which EPDM does not tolerate.
2. Keep tracks and gasket grooves free of grit, which cuts the rubber.
3. Replace with a matching profile; gaskets come in many shapes and the wrong one will not seal.

Where FabWise uses it

Gasket specification is part of the window, door and facade quote after the site visit, for the aluminium sliding window, uPVC window and windows and doors range. For noise, read soundproof windows in Delhi NCR.