🏢BS 8233:2014 · United Kingdom

Open Plan Office Acoustic Design to BS 8233:2014

Open plan offices present a unique acoustic paradox: speech must be intelligible within conversation groups but unintelligible beyond the distraction distance to preserve privacy and concentration. ISO 3382-3:2012 defines the key metrics — spatial decay rate D2,S, distraction distance rD, and A-weighted SPL of speech at 4 m (Lp,A,S,4m).

TL;DR

Under BS 8233:2014, a open plan office of 400-600 m³ (typical dimensions 20m × 10m × 2.8m) requires an RT60 of ≤ 0.8s at 500-2000 Hz. Background noise must not exceed 40 dBA. BS 8233:2014 Table 4 recommends RT60 <= 0.

RT60 Target

≤ 0.8s

Noise Limit

40 dBA

STI Minimum

N/A

Frequency Range

500-2000 Hz

Specific Requirements

Parameter	Target	Clause Reference	Notes
Reverberation Time (RT60)	≤ 0.8s	§7.7	500-2000 Hz, Furnished, unoccupied
Background Noise Limit	≤ 45 LAeq,T	Table 4	HVAC + building services, unoccupied
Frequency Range	500-2000 Hz	—	Octave bands for compliance assessment

Step-by-Step Compliance Calculation

1
Establish design target
Set RT60 <= 0.8s per BS 8233 Table 4 for open-plan offices. Consider tighter targets if WELL or BREEAM certification is pursued.
2
Calculate total absorption needed
Use Sabine equation with room volume. Open-plan offices need large absorption areas due to high volume-to-surface ratio.
3
Design ceiling treatment
Specify high-NRC ceiling tiles covering at least 85% of ceiling area. Supplement with suspended rafts if soffit is exposed.
4
Add vertical absorption
Install absorptive desk screens (min 400mm above desk), wall panels, and freestanding absorbers to reduce lateral reflections.
5
Verify post-occupancy
Measure RT60 at representative positions per ISO 3382-2 to confirm compliance with BS 8233 target.

Recommended Materials

Surface	Material Category	Min NRC	Coverage %
Ceiling	Mineral wool ceiling tile	0.90	85%
Desk screens	Absorptive desk divider	0.80	100%
Floor	Carpet tile	0.25	100%

Browse the full acoustic materials database for absorption coefficients and product specifications.

Common Failure Modes

⚠️Exposed soffit design

Trendy exposed concrete ceilings without compensating treatment produce RT60 of 1.2-1.5s, far exceeding the 0.8s target.

⚠️Insufficient desk screening

Low or absent desk dividers allow direct speech paths between workstations, creating distraction even with low RT60.

⚠️Breakout kitchen noise

Open-plan kitchenettes without acoustic separation transmit appliance and social noise across the office floor.

Frequently Asked Questions

What RT60 does BS 8233:2014 require for a open plan office?

BS 8233:2014 requires a reverberation time of ≤0.8s at 500-2000 Hz for open plan office spaces. BS 8233:2014 Table 4 recommends RT60 <= 0.8s for large open offices with ambient noise of 35-40 dBA. The standard provides general guidance but does not prescribe speech privacy metrics. For detailed open-plan performance, ISO 3382-3 parameters are more appropriate.

What is the maximum background noise level for a open plan office under BS 8233:2014?

BS 8233:2014 sets a maximum background noise level of 40 dBA for open plan office spaces. This includes noise from HVAC systems, building services, and external intrusion, measured with the room unoccupied. Exceeding this limit degrades speech intelligibility and occupant comfort.

How much acoustic treatment does a open plan office need to comply with BS 8233:2014?

A typical open plan office (400-600 m³) requires Mineral wool ceiling tile (NRC ≥0.9) covering 85% of the ceiling as the primary treatment. Additional wall absorption on 2 surface(s) is typically needed. Use the AcousPlan calculator with the pre-loaded dimensions (20m × 15m × 2.8m) to calculate the exact absorption deficit for your room.

Calculate BS 8233:2014 Compliance for Your Open Plan Office

Pre-loaded with typical open plan office dimensions (20m × 15m × 2.8m) and an RT60 target of 0.8s per BS 8233:2014. Enter your actual dimensions, select materials, and verify compliance instantly.

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