UMBRELLA WASHERS

Product Specification :
Umbrella Washers, also known as Bonded EPDM Washers, are specialized fasteners consisting of a dome-shaped metal backing permanently bonded to a resilient rubber-like gasket. They are specifically engineered to provide a water-tight and weather-proof seal in roofing, siding, and exterior cladding applications.
+1

1. Anatomy and Design
The "Umbrella" effect comes from the convex shape of the metal part, which distributes pressure evenly and protects the seal from UV degradation.
Metal Backing: A curved (domed) disc that provides structural rigidity and prevents the screw head from pulling through the material.
Sealant Layer: A slightly smaller diameter layer of EPDM (Ethylene Propylene Diene Monomer) or Neoprene bonded to the underside.

2. Material Specifications
Component    Material Options    Properties
Metal Backing    Galvanized Steel    Economical, standard for residential roofing.
    Stainless Steel (304/316)    Maximum rust resistance; essential for coastal areas.
    Aluminum    Lightweight; used with aluminum sheeting to prevent electrolysis.
Gasket    EPDM Rubber    High resistance to heat, ozone, and extreme weathering.
    Neoprene    Good oil resistance, though less UV stable than EPDM.

3. Key Technical Features
Compression Seal: When the fastener is tightened, the EPDM layer is compressed into the hole and around the screw threads, blocking water ingress.
Vibration Dampening: The rubber layer absorbs thermal expansion and contraction of metal sheets, preventing the fastener from loosening or "chattering."
Corrosion Barrier: The washer acts as an insulator, preventing "galvanic corrosion" between the fastener and the roofing sheet if they are made of different metals.

4. Common Dimensions
Umbrella washers are sized based on the outer diameter (OD) of the washer and the inner diameter (ID) of the hole (to match the screw gauge).
Washer Size (OD)    Typical Screw Gauge    Primary Use
14mm    #10 / #12 Screws    Standard metal roofing.
16mm    #12 / #14 Screws    Industrial cladding.
19mm / 25mm    Heavy Bolts / M6+    Large skylights and heavy structural panels.

5. Installation Performance
The success of an umbrella washer depends entirely on the tightness of the screw.
Under-Tightened: The EPDM is not compressed enough; water can seep under the washer.
Correctly Tightened: The metal dome is slightly flattened, and the EPDM is visible just at the edge of the metal, but not bulging out.
Over-Tightened: The metal dome inverts or the EPDM is crushed and "squashed" out. This destroys the seal and causes the rubber to fail prematurely due to UV exposure.

6. Applications
Metal Roofing: Securing corrugated iron or standing seam panels.
Solar Panel Mounting: Sealing the penetration points of mounting brackets.
HVAC: Sealing ductwork penetrations on rooftops.
Polycarbonate Sheets: Fixing clear or tinted patio roofing where thermal movement is high.