Key takeaways
- EPDM resists UV, ozone and temperature cycling far better than neoprene or PVC.
- Bonded washers stay centred and cannot spin off during driving.
- Correct driving compresses the rubber so it just reaches the edge of the steel backing.
The washer is the only thing between rain and the hole your screw just drilled. A good one lasts as long as the roof sheet.
Why EPDM
Ethylene propylene diene monomer rubber keeps its elasticity from about −40 °C to +120 °C and resists UV and ozone cracking. Cheap PVC or recycled rubber washers harden and split within a few years.
Bonded vs loose
We vulcanise the EPDM to a steel or stainless backing washer. Bonding keeps the rubber centred on the hole and stops it spinning off as the screw drives.
Washer size
| Washer OD | Use |
|---|---|
| 14 mm | Side lap and stitching screws |
| 16 mm | Standard roof sheet to purlin |
| 19 mm and larger | Sandwich panels, fibre cement, translucent sheets |
Reading the washer after driving
- Under-driven: rubber not touching the sheet all round. Water will get in.
- Correct: rubber compressed and just visible at the edge of the backing washer.
- Over-driven: rubber squeezed out beyond the backing, sheet dimpled. The seal will fail early.
Use a screw gun with a depth-locating nosepiece to get it right every time.
Frequently asked questions
Can I buy EPDM washers separately?
Yes. We supply bonded washers in 12–25 mm OD, with galvanised, stainless or aluminium backing.
What colour EPDM should I choose?
Black is standard and has the best UV resistance. Grey is available to blend with light-coloured sheet.
