PAC International RSIC-Joist Isolator
The PAC International RSIC-Joist Isolator is a resilient cap that seats over the top of a wood joist so the subfloor above is decoupled from the joist framing below. It preserves floor buildup height while breaking the direct impact and vibration path between finished floor and joist — the workhorse detail for high-IIC wood-framed floor assemblies in multifamily and residential retrofits.
- True Joist Decoupling: Seats over the joist top so subfloor screws land in the isolator's steel cap, never into the joist itself — eliminating the rigid bridge that defeats most retrofits.
- Zero Extra Floor Height: Adds only the isolator's cap thickness to floor buildup — the go-to option when finish-floor height is fixed by doors, transitions, or code.
- Retrofit-Friendly: Drops onto exposed wood joists during rough-in — no reframing, no floating floor cassette, no concrete topping required.
- Consistent Layout: Set one isolator per joist at the manufacturer's recommended on-center spacing so load and deflection stay uniform across the floor plate.
Online orders up to 4,999 pieces. For anything larger, call (415) 864-4440 and we'll price the project with you.
Volume pricing
$2.99 per isolator. Order 250+ isolators and pay $2.89 per isolator — an extra $0.10 off per isolator for each additional 250 isolators, down to a $2.10 per isolator floor.
Discounts apply automatically in the cart and count boxes and cases toward the total.
RSIC-Joist Isolator Specifications
- Application
- Wood-joist floor decoupling under subfloor
- Overall width
- 2.13 in.
- Overall height
- 1.93 in.
- Base thickness
- 0.43 in.
- Isolation element
- Molded rubber U-cap that seats over the joist top
- Layout
- One isolator per joist at project-engineered on-center spacing (typ. 16 in. o.c.)
- Mounting
- Seats over joist top — subfloor screws land in the isolator's cap, never the joist
- Compatible framing
- Nominal 2× wood joists — I-joists on request
Rockwool Safe'N'Sound R11
- R-Value
- R-11
- Material
- Stone wool (basalt rock + recycled slag)
- Framing fit
- 2×4 stud and joist cavities, 16" or 24" o.c.
- Density
- Higher than standard fiberglass batt
- Fire performance
- Non-combustible, melting point ~2,150°F
- Water repellency
- Water-repellent, won’t support mold growth
- Install method
- Friction-fit; cut with a long serrated knife
- Coverage
- Approx. 60 sq ft per bag
RSIC-Joist Isolator Project Calculator
Enter your surface square footage. We'll return a clip, channel, and screw count for your project — calculations run on our servers so estimates stay accurate as our field data improves.
- Rockwool insulation
- Direct-mount clips
- Mass-loaded vinyl (MLV)
- Acoustic sealant
Adds MLV over Good for a denser limp-mass layer.
One isolator per joist at the manufacturer's on-center spacing. Confirm layout with an acoustic engineer and add a 10% coverage buffer for cuts and re-work.
IIC Gauge
Compare how the RSIC-Joist Isolator performs across assembly tiers. Select an assembly below to see the resulting IIC score.
Joist Isolators + Rockwool + MLV + double subfloor with Green Glue between layers.
- 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 RSIC-Joist Isolator compares
| Model | Primary Use | Framing | Typical Layout | Isolation Element |
|---|---|---|---|---|
| RSIC-Joist Isolatorthis | Decouple subfloor from wood joists | Wood joists (2× and I-joist) | One isolator per joist | Molded rubber isolator in steel cap |
| IFB1 | Under sleepers / subfloor over deck | Concrete or continuous deck | Project-engineered grid | Molded rubber pad |
| RSIC-U | Universal clip for specialty framing | Mixed / non-standard | Project-specific | Molded rubber isolator |
Applicable Assemblies
See where the RSIC-Joist Isolator fits — from budget baseline to studio-grade isolation.
Best — Joist Isolator + Rockwool + MLV + Double Subfloor + Green Glue
Wood joists · RSIC-Joist Isolators over joist tops · Rockwool cavity · MLV underlay · double subfloor with Green Glue between layers · finished floor · perimeter acoustic sealant.
Better — Joist Isolator + Rockwool + Double Subfloor + Green Glue
Wood joists · RSIC-Joist Isolators · Rockwool cavity · double subfloor with Green Glue between layers · finished floor · perimeter acoustic sealant.
Good — Joist Isolator + Rockwool + Subfloor
Wood joists · RSIC-Joist Isolators over joist tops · Rockwool cavity · single subfloor · finished floor · perimeter acoustic sealant.
