How many knives do I need for my project?

One knife per active crew is the standard recommendation. On multi-story or multi-crew jobs, plan one knife per two installers.

How do I cut cleanly with it?

Score the batt on a plywood scrap or Speed Square, then draw the serrated blade through in one long stroke rather than sawing. For notches, mark both faces of the batt and cut from the finish side.

Can I use this on fiberglass insulation instead?

The blade works on fiberglass, but a standard utility knife is usually sufficient for fiberglass — reserve this knife for the denser Rockwool stone-wool batts we recommend for soundproofing.

Do I need to sharpen the blade?

The serrated edge stays sharp for the life of a typical project. Replace the knife when cuts start dragging or edges begin to tear rather than slice.

Grip-Rite Tools

Grip-Rite Stone Wool Knife

Name: Grip-Rite Stone Wool Knife
Brand: Grip-Rite
SKU: GR-STONE-KNIFE
Price: 19.99 USD
Availability: InStock

The Grip-Rite Stone Wool Knife is a serrated blade purpose-built for Rockwool stone-wool insulation. It rides through dense mineral fiber without compressing the batt, so cuts stay square and cavities pack cleanly to the stud face. Sized right for one-handed use over a scrap plywood or Speed-Square cutting jig — the standard on Rockwool installs and a straight upgrade from a utility knife on stone-wool batts.

Grip-Rite Stone Wool Knife — serrated fixed-blade insulation knife with red handle for cutting Rockwool batts. — Grip-Rite Stone Wool Knife — serrated blade with ergonomic red handle.

Purpose-Built for Stone Wool: Serrated edge slices dense Rockwool without dragging or compressing the batt like a straight utility blade.
Clean Complex Trims: Notch around wiring, outlet boxes, plumbing, and blocking without tearing the fiber — essential for tight fill on decoupled walls.
One-Handed Control: Ergonomic grip and blade length let you cut standing over a plywood jig or Speed Square, keeping cuts square and safe.
Pairs with Every Rockwool Product: Recommended companion for Safe'N'Sound R11, Comfortbatt R13, and Comfortbatt R15 installs — one knife per crew.

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Rockwool RecommendedSerrated BladeOne-Handed Cut

Product Specs

Stone Wool Knife Specifications

Use: Cutting Rockwool stone-wool insulation batts
Blade Type: Serrated, purpose-built for mineral fiber
Compatibility: Safe'N'Sound R11, Comfortbatt R13, Comfortbatt R15
Note: One knife per crew is standard — additional units for multi-crew jobs

Product Comparison

How Stone Wool Knife compares

Model	Primary Use	Blade Type	Best For	Notes
Grip-Rite Stone Wool Knifethis	Cutting Rockwool batts	Serrated, purpose-built	All stone-wool installs	One knife per crew
Standard Utility Knife	General trades	Straight snap-off blade	Drywall, boxes, film	Compresses stone wool; ragged cavities
Bread / Serrated Kitchen Knife	Improvised cut	Serrated	Emergency only	Not job-site safe; not warrantied

Soundproofing Solution — Walls

Applicable Assemblies

See where the Stone Wool Knife fits — from budget baseline to studio-grade isolation.

BestSTC 60

Diagram coming soon

Best — Drywall + Studs + Insulation + Clips & Channels + MLV + Drywall + Green Glue + Drywall

Tight-packed Rockwool cavities depend on square, clean batt trims — this knife makes them possible.

View assembly

BetterSTC 54

Diagram coming soon

Better — Drywall + Studs + Insulation + Clips & Channels + Drywall + Green Glue + Drywall

Clean batt trims maintain cavity density around wiring, boxes, and blocking.

View assembly

GoodSTC 48

Diagram coming soon

Good — Drywall + Studs + Insulation + Clips & Channels + Drywall

Every Rockwool install benefits from a purpose-built serrated blade.

View assembly

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FAQ

Stone Wool Knife — Common Questions

Stone-wool batts are dense enough that a standard utility blade compresses the fiber instead of cutting it — leading to ragged edges, uneven cavity fill, and lost R-value. A serrated stone-wool blade slices cleanly through the batt at full density.