🏫BB93:2015 · United Kingdom

Classroom Acoustic Design to BB93:2015

Classrooms are the most acoustically critical room type in education buildings, where speech intelligibility directly determines learning outcomes. A well-designed classroom achieves an unoccupied RT60 of 0.

TL;DR

Under BB93:2015, a classroom of 150-300 m³ (typical dimensions 10m × 7m × 3m) requires an RT60 of ≤ 0.6s at 500-2000 Hz. Background noise must not exceed 35 dBA. BB93:2015 is the UK Department for Education mandatory performance standard for school acoustics.

RT60 Target

≤ 0.6s

Noise Limit

35 dBA

STI Minimum

N/A

Frequency Range

500-2000 Hz

Specific Requirements

Parameter	Target	Clause Reference	Notes
Reverberation Time (RT60)	≤ 0.6s	§1.4	500-2000 Hz (Tmf), Unoccupied, furnished, primary
Background Noise Limit	≤ 35 LAeq,30min	Table 1.2	HVAC + building services, unoccupied
Frequency Range	500-2000 Hz	—	Octave bands for compliance assessment

Step-by-Step Compliance Calculation

1
Identify BB93 room type
Classify the room per BB93 Table 1.2. Standard classrooms, SEN rooms, music rooms, and halls have different targets.
2
Set RT60 target
Standard classrooms: 0.6s. SEN classrooms: 0.4s. Open plan areas: 0.8s. Music rooms: 0.8-1.2s.
3
Calculate absorption requirement
Use Sabine equation to determine total absorption at 500, 1000, and 2000 Hz for the target RT60.
4
Design treatment scheme
Specify ceiling tiles, wall panels, and floor finish to meet absorption target within budget constraints.
5
Assess indoor ambient noise
Calculate noise ingress from HVAC, external sources, and adjacent rooms. Must not exceed 35 dB LAeq,30min.
6
Submit acoustic report
Prepare BB93 compliance report for DfE approval, including predicted RT60, noise levels, and sound insulation values.

Recommended Materials

Surface	Material Category	Min NRC	Coverage %
Ceiling	Mineral wool ceiling tile	0.85	85%
Rear wall	Fabric-wrapped absorber	0.80	50%
Floor	Carpet or vinyl with underlay	0.20	100%

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

Common Failure Modes

⚠️SEN rooms missing 0.4s target

Rooms designated for pupils with special educational needs require 0.4s RT60, which demands significantly more absorption than standard classrooms.

⚠️Noise from adjacent sports hall

Inadequate sound insulation between classrooms and sports halls or music rooms causes background noise exceedances.

⚠️Natural ventilation noise

Opening windows for ventilation admits external traffic noise exceeding 35 dBA, but closing them causes overheating in summer.

Frequently Asked Questions

What RT60 does BB93:2015 require for a classroom?

BB93:2015 requires a reverberation time of ≤0.6s at 500-2000 Hz for classroom spaces. BB93:2015 is the UK Department for Education mandatory performance standard for school acoustics. It requires RT60 <= 0.6s for standard classrooms and <= 0.4s for rooms used by pupils with special hearing needs. Indoor ambient noise levels must not exceed 35 dB LAeq,30min. Compliance is a condition of DfE funding approval.

What is the maximum background noise level for a classroom under BB93:2015?

BB93:2015 sets a maximum background noise level of 35 dBA for classroom 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 classroom need to comply with BB93:2015?

A typical classroom (150-300 m³) requires Mineral wool ceiling tile (NRC ≥0.85) 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 (8.5m × 7m × 2.9m) to calculate the exact absorption deficit for your room.

Calculate BB93:2015 Compliance for Your Classroom

Pre-loaded with typical classroom dimensions (8.5m × 7m × 2.9m) and an RT60 target of 0.6s per BB93:2015. Enter your actual dimensions, select materials, and verify compliance instantly.

Open Calculator with Preset