Same mass, two differences
The three grades are the same sheet in every way that governs quantities and installation: nominally 5 kg/m² at about 3 mm according to the manufacturer’s datasheet, 1 m × 5 m rolls, bonded with BA990, sealed with BA890, ordered with the same 20% allowance. What you pay for above the standard grade is one of two things: independent fire evidence, or a formulation tuned for low frequency. Not more mass.
| BB830 | BB830FR | BB830LF | |
|---|---|---|---|
| Role | Standard grade | Fire-classified grade | Low-frequency grade |
| Areal density, thickness (nominal) | about 5 kg/m² at 3 mm | about 5 kg/m² at 3 mm | about 5 kg/m² at 3 mm |
| Acoustic figure for the material | STC 32, laboratory value, manufacturer data | Equivalent to the standard grade, manufacturer data | Formulated for low frequency, manufacturer data |
| Fire evidence | MVSS 302 and SAE J369, manufacturer data | AS/NZS 1530.3:1999, indices 0/0/0/7, SGS report AJFTS26000525R01_EN — independent | MVSS 302 and SAE J369, manufacturer data |
| Price per m² | 1,122 (1,049) | 1,288 (1,204) | 1,761 (1,646) |
| Price per 5 m² roll | 5,612 | 6,442 | 8,806 |
| Premium over BB830 | — | +166/m² (about 15%) | +639/m² (about 57%) |
| 1 m² trial piece | Yes, 1,122 | No | No |
By situation
| Situation | Grade | Why |
|---|---|---|
| Condominium bedroom, party wall, speech and television | BB830 | Speech is a mid-frequency problem and a private dwelling carries no fire requirement on wall linings. The premium grades buy nothing here |
| Drain stacks and ducts in a residential shaft | BB830 | Mid-frequency; the standard mass is what the lagging needs |
| Hotel, restaurant, bar, office fit-out, school, hospital | BB830FR | Public assembly spaces carry a fire requirement and concealed materials are what inspection asks about |
| Any shaft, riser or ceiling void where the building specifies fire-classified materials | BB830FR | The building’s requirement governs |
| Rehearsal room, karaoke room, home theatre, drum room | BB830LF | The complaint is bass, and the LF formulation is made for that range |
| Plant rooms: pumps, blowers, compressors, generators | BB830LF | Machinery noise is dominated by low frequency |
| A venue with both a fire requirement and a bass complaint | FR in the public areas, LF on the demising wall | Split by where the wall sits, not one grade for the whole job |
| Enclosures near hot work or welding | BB830FR | The fire risk is on site, not in the code |
| Back of house, stores, plant rooms with no specific requirement | BB830 | No reason to pay more |
Three questions that settle it
- Does the space carry a fire requirement, or will an inspector ask for evidence on the material? If yes, BB830FR, and the decision is made.
- Is the complaint bass, machinery or a thump that carries no tune? If yes, BB830LF — and read the music-room page first, because no sheet does that job on its own.
- If neither, BB830, and put the difference into sealant, the door and the penetrations, where it returns more than a grade change would.
Where the money goes wrong
- Buying LF for a speech problem. Speech sits in the mid band where the standard grade already performs; the 57% premium returns nothing audible.
- Buying FR because it is assumed to be acoustically better. It is acoustically equivalent to the standard grade according to the manufacturer. The premium is for the fire evidence, not for decibels.
- Lining a hotel corridor with the standard grade and being asked for a fire report at inspection. The material then comes out, which costs far more than the 15% premium would have.
- Expecting LF alone to fix a subwoofer through a party wall. Mass is weakest at low frequency whatever the formulation; cavity depth, decoupling and mineral wool do the work and the sheet is one component.
- Mixing grades on one wall to save money. If a wall must be FR, all of it must be FR, because the fire evidence is asked of the whole assembly.
What is the same for all three
- Rolls of 1 m × 5 m, about 25 kg, sold whole.
- Order about 20% over the measured area for overlaps and offcuts, rounded up to whole rolls.
- BA990 adhesive at roughly one cartridge per 3 m², BA890 sealant at roughly one per 3 m², BA650 putty pads per socket box.
- Heat tolerance 93 °C according to the manufacturer; not for surfaces hotter than that.
- All published figures are laboratory values. Field results are normally 5 to 10 dB lower, and sealing decides more than the grade does.