Bonded Sealing Washer
Washers · sealing washer · neoprene washer · bonded washer · EPDM washer
Definition: A bonded sealing washer has a rubber sealing ring bonded to a steel washer, sealing the fastener hole against water and air — used in roofing and enclosures.
Anatomy
■ Body■ Hole
Governing standards: Manufacturer specified (no universal standard)
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| for #10 | M5 | 0.75 OD | seal 0.06 |
| for #12 | M6 | 0.87 OD | seal 0.06 |
| for 1/4 | M6 | 1 OD | seal 0.08 |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Neoprene | steel + neoprene | — | General purpose |
| EPDM | steel + EPDM | — | Outdoor/UV resistant |
Materials
- Steel + neoprene
- Stainless + EPDM
- Galvanized + EPDM
Pros & Cons
Pros
- Seals the hole against water and air
- One-piece — nothing to lose
- Absorbs light vibration
Cons
- Seal degrades over time and heat
- Only works with the matching screw size
- Rubber hardens and cracks in UV over years
Typical Uses
- Metal roofing screws
- Enclosures and junction boxes
- Gutters and flashing
- Siding
Alternatives & Related
- Flat Washer — Load spreading without sealing
- Self-Drilling Screw — The roofing screw a sealing washer pairs with
Where to Buy
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FAQ
Neoprene or EPDM sealing washer?
Neoprene is fine indoors and mild conditions; EPDM handles UV and weather better for outdoor roofing and siding.
Where does a sealing washer go?
Under the screw head, so the rubber ring compresses against the panel and seals the fastener hole.