Acoustic plasterboard is the obvious dense lining for many internal soundproofing systems—but it is not always the right board. Wet rooms, external-facing assemblies, plant areas, fire-sensitive spaces and tough commercial environments can place demands on a lining that standard gypsum products were never intended to handle.
Quietstone Cem-Rock 12mm is a dense cement-fibre board that combines useful mass with A1 non-combustible fire performance, water resistance and external durability.
What is Cem-Rock?
Cem-Rock is a 2400 x 1200 x 12mm cement-fibre building board with an average mass of 11.6kg/m², approximately 33.4kg per sheet, and density around 950kg/m³. It is classified A1 to EN 13501-1 and is designed for demanding dry, humid, external and fire-sensitive applications.
Cem-Rock vs acoustic plasterboard
| Feature | Cem-Rock | Acoustic plasterboard | Acoustic absorber |
|---|---|---|---|
| Main job | Dense, robust lining / mass | Dense internal lining / mass | Reduce cavity or room reflections |
| Wet areas | Strong option | Depends on board and system | Product-specific |
| External use | Yes, when correctly specified and fixed | Normally no | Product-specific |
| Fire | A1 EN 13501-1 | Board-specific | Product-specific |
| Role in soundproofing | Add mass and robustness | Add mass and finish | Absorption |
Where Cem-Rock makes more sense
- Wet rooms, pools and saunas
- External or semi-exposed build-ups
- Fireplaces, chimneys, boiler and plant rooms
- Factories and workshops
- Curved surfaces
- Soundproof walls where robustness, fire and water performance matter together
How to use Cem-Rock in a soundproof wall
Wall performance normally comes from several layers working together:
- Cavity absorption: Rockwool RWA45 or Rockwool RW3.
- Isolation: clips and channels where the construction needs decoupling.
- Mass: Cem-Rock with a suitable dense lining, or an acoustic membrane / MLV where appropriate.
- Airtightness: seal edges and penetrations with AC50 acoustic sealant or the specified fire/acoustic sealant.
- Flanking: check adjoining floors, ceilings and side walls rather than treating the main partition in isolation.
Browse our wall soundproofing and ceiling soundproofing ranges for the other layers.
Useful Cem-Rock technical points
| Size | 2400 x 1200 x 12mm |
| Average mass | 11.6kg/m² |
| Density | 950kg/m³ |
| Reaction to fire | A1 – EN 13501-1 |
| Bending strength | ≥6.2MPa |
| Published bending radius | 2.0m |
| Thermal conductivity | 0.39W/mK |
| Water / freeze-thaw / mould tests | Pass |
Can Cem-Rock be curved?
Yes. Quietstone publishes a bending radius of approximately 2m, which can make the board useful on selected curved walls and architectural details. The supporting frame, jointing and fixing arrangement still need to suit the radius and application.
Should you replace acoustic plasterboard with Cem-Rock everywhere?
No. For ordinary dry internal rooms, acoustic plasterboard can remain the simpler and more economical lining. Cem-Rock becomes particularly attractive where acoustic mass needs to coexist with A1 fire performance, water resistance, external durability, impact resistance or curved construction.
Get the build-up checked before ordering
Send us the existing wall or ceiling construction, dimensions, the type of noise, the available build-up depth and any wet-area, external or fire constraints. Soundproofing King can help choose the other components instead of relying on one board in isolation.
