W20R Sound Isolation Washer
The W20R Sound Isolation Washer is used in assemblies where a resilient underlayment (like PAC Resilmat RMI) is placed under perimeter plates on floor and ceiling separation walls. Fastening through the underlayment without a resilient washer creates a rigid short-circuit that transmits structure-borne noise past the barrier. The W20R keeps the flanking path decoupled at every fastener.
- Simplified Mechanical Attachment: W20R Washer allows straightforward mechanical fastening of resilient underlay to flooring or ceiling sills without crushing or displacing the rubber layer during installation.
- Maintains Acoustic Integrity: By preserving the decoupling effect of underlay at fastening locations — points that otherwise become rigid connections — it provides preventative measures to avoid sound short-circuiting where structure-borne noise would easily transmit across fastener point.
- Versatile Across Assemblies: Applicable to both floor and ceiling sills in wood or steel framing environments where underlay is deployed.
- Consistent Installation Pattern: Regularly spaced washers ensure a uniform fastening pattern, supporting installation quality and predictable performance.
Online orders up to 1,000 washers. For anything larger, call (415) 864-4440 and we'll price the project with you.
W20R Washer Specifications
- Width
- 1 3/8"
- Height
- 1/2"
- Weight
- 0.02 lb
- Max Spacing
- 24" O.C. on center
- Composition
- Resilient rubber body over a steel washer core
- Purpose
- Decouples mechanical fasteners across resilient underlay
- Application
- Effective with cork or materials with elastic recovery — made for membranes designed to bear point loads.
- Companion
- Designed for use with PAC Resilmat RMI resilient mat
Resilmat RMI mat
- Roll width
- 3-1/4"
- Thickness
- 5 mm
- Roll length
- 15 ft or 30 ft
- Bearing pressure range
- 1–50 PSI
- Use with
- W20R washers at every plate fastener (16"–24" o.c.)
W20R Washer Project Calculator
Enter the combined length of your top and bottom plate runs (i.e. wall perimeter × 2) — we'll size the W20R washer count at 24" on-center.
STC Gauge
Compare how the W20R Washer performs across assembly tiers. Select an assembly below to see the resulting STC score.
Sill plate fastened directly to substrate — flanking path fully coupled.
- STC 30-39: Loud speech clearly audible next room.
- STC 40-49: Loud speech muffled — normal residential wall.
- STC 50-59: Loud speech barely audible; suitable for offices & multi-family.
- STC 60+: Approaches studio-grade isolation.
How W20R Washer compares
| Model | Best For | Isolation Mechanism | Where It Lives | Notes |
|---|---|---|---|---|
| W20R Washerthis | Anchors through resilient underlay | Resilient washer prevents hard contact at fastener | Sill plate / perimeter track to slab | Targets a common weak point: fastener short-circuiting |
| Resilient Underlay (rubber) | Plate/track decoupling | Continuous resilient layer | Under the full track/plate run | Needs correct fastening approach to avoid bridging |
| Clips & Channel (system) | High-performance decoupled wall/ceilings | Decouples drywall from structure | Studs/joists behind gypsum | Pairs well with isolated perimeter details |
Applicable Assemblies
See where the W20R Washer fits — from budget baseline to studio-grade isolation.
Best — Stud-Wall Foundation w/ RMI Mat + W20R Washers
Stud wall assembled with insulation, clips & channel system, MLV, Green Glue, and finished with acoustic sealant.
Better — Stud Wall + RMI Mat + W20R Washers
Stud-wall foundation assembled with insulation, clips & channels, Green Glue, drywall, and finished with acoustic sealant.
Good — Perimeter Isolation Only
Stud-wall foundation assembled with insulation, clips & channels, silent FX drywall, and finished with acoustic sealant.
