Open-plan office noise: limits, space and desk sharing

In an open-plan office, ASR A3.7 limits noise by activity: no more than 55 dB(A) for work requiring high concentration and no more than 70 dB(A) for clerical work. On top of that comes a reverberation time of no more than 0.6 seconds. ASR A1.2 governs space, with 12 to 15 square metres per workstation as the planning value. Desk sharing is allowed but belongs in the risk assessment.

Noise, space and desk sharing are part of the risk assessment under section 5 ArbSchG. This article shows which values apply in an open office, how to work them through and which measures stand up to an inspection.

Which noise limits apply in an open-plan office?

The noise limit in an open-plan office depends on the activity, not on the room. ASR A3.7 divides activities into three categories: 55 dB(A) for high concentration or high speech intelligibility, 70 dB(A) for medium concentration such as clerical work, and for routine work no fixed value but a duty to reduce. Two limits can therefore apply in the same room.

Under ASR A3.7, the rating level is the quantity that characterises the typical noise exposure of an activity. It consists of the measured continuous sound level plus surcharges for prominent tones and impulses. The rating level is therefore not a peak value but an average over the typical working situation.

ASR A3.7 explicitly lists meetings and negotiations in conference rooms as well as scientific and creative work under activity category I. Category II covers scheduling, data entry, word processing and clerical office work. Concept work, editing or programming can be assigned to category I depending on how much concentration they require. The employer makes the assignment in the risk assessment, and it determines which limit applies at the desk.

Volume alone is rarely the problem in an office. What disturbs people is intelligible conversation at the next desk: speech you cannot help overhearing interrupts focused work more than an even background sound. That is why ASR A3.7 requires room acoustic measures, meaning a short reverberation time, in addition to the levels.

The Workplace Ordinance sets the protective goal in annex no. 3.7 ArbStättV: the sound pressure level in workplaces must be kept as low as the nature of the business allows. The level values of ASR A3.7 are the way to meet this goal verifiably.

Reverberation time: the value that does most in an open office

Under ASR A3.7, the reverberation time is the time in which the sound pressure level drops by 60 decibels after a sound ends. For multi-person and open-plan offices, section 5.2.1 of ASR A3.7 sets a reverberation time of 0.6 seconds, measured in the unoccupied room between 250 and 2,000 hertz. The shorter the reverberation, the less speech carries across the room.

An open room with a concrete ceiling, glass façade and smooth floor reverberates well beyond 0.6 seconds. Sound-absorbing surfaces help, in this order of effect:

• Ceiling: an acoustic ceiling or suspended absorbers above the desks are the largest continuous surface and do the most.
• Walls and back walls: absorbers on walls opposite glass surfaces stop sound bouncing between hard surfaces.
• Screens and furniture: tall, absorbent partitions between desk clusters and cabinets with acoustically effective fronts provide shielding.
• Floor: carpet mainly reduces footstep and chair castor noise.

Reverberation time vs. rating level means: the level describes how loud it is, the reverberation time how far speech carries. An office can stay within 55 dB(A) and still be hard to use because every phone call at the other end of the room remains intelligible. Measuring only the level misses the most common cause of complaints.

How much space does an open-plan office need?

Under ASR A1.2, an open-plan office needs at least 8 square metres for the first and 6 square metres for each further workstation. As the planning value for open-plan offices, ASR A1.2 gives 12 to 15 square metres per workstation, including furniture and a share of circulation space. At the desk itself, a free movement area of at least 1.50 square metres must remain, at least 1.00 metre wide and deep.

The higher planning value compared with cellular offices (8 to 10 square metres) is no coincidence: more space per desk means more distance between sources of conversation and therefore less disturbance. All room dimensions in detail are in the article on the Workplace Ordinance in the office.

Three worked examples:

• Agency, 10 fixed workstations on 120 square metres. The minimum floor area is 8 plus 9 times 6, so 62 square metres, and is met. At 12 square metres per desk, the space reaches exactly the lower planning value. There is no room for extra desks.
• Consultancy, 30 employees with desk sharing, 20 desks on 200 square metres, clear height 2.80 metres. The calculation uses desks, not heads: 10 square metres per desk is below the open-plan planning value. The minimum floor area of 122 square metres is met, and the air space of 560 cubic metres gives 28 cubic metres per person present, well above the required 12. Above 100 square metres, the height is only sufficient with a justified reduction to 2.75 metres.
• Administration, 25 workstations on 400 square metres. At 16 square metres per desk, the space is above the planning value. Here acoustics, not space, decide: large open rooms rarely achieve 0.6 seconds of reverberation without ceiling absorbers.

Desk sharing: what occupational safety requires

Desk sharing is an organisational form in which several employees share fewer workstations instead of each person having a fixed desk. No law prohibits desk sharing. Every shared desk must, however, meet the requirements for display screen workstations under annex no. 6 ArbStättV and be adjustable for changing users.

DGUV Information 215-441 "Office space planning" covers desk sharing in section 4.7 and names the typical drawbacks: more effort to adapt workstations to different body sizes, more organisation, more frequent cleaning and no way to personalise the desk. These drawbacks give the points a risk assessment for desk sharing has to cover:

• Adjustability: height-adjustable desk, chair with adjustable seat height and backrest, monitor adjustable in height and tilt. The article on the display screen workstation shows what this looks like at the desk.
• Safety training: anyone using a different desk every day must know how to adjust it. That belongs in the annual safety training.
• Quiet zones: retreat rooms for phone calls and focused work take category I activities out of the open floor.
• Personal storage and cleaning: lockers and a clean-desk rule so that desks are actually handed over free and clean.

Desk sharing also changes attendance, and first aid and fire safety depend on it. Under section 26 DGUV Regulation 1, an administrative business needs one first aider for 2 to 20 insured persons present and 5 percent from 21 present. Anyone who schedules first aiders for working from home quickly has too few on site on full office days. The first aider calculator shows the number per attendance level.

Psychological stress in the open office

Disturbance from conversations, phone calls and walkways is psychological stress within the meaning of section 5(3) no. 6 ArbSchG and belongs in the risk assessment. In an open-plan office it is often a bigger hazard than the level itself: frequent interruptions, no places to retreat to and the feeling of being watched all the time.

Open-plan office vs. cellular office, from an occupational safety point of view: the open-plan office makes coordination easier and saves space but needs more design work on acoustics, zoning and rules. The cellular office protects concentration, makes exchange harder and needs more space per person. Neither is legally required. How to record psychological stress systematically is described in the article on psychological stress in the risk assessment.

How to assess noise and space in an open-plan office

A robust risk assessment for an open-plan office follows five steps: classify activities, check space and occupancy, measure acoustics, ask employees, document measures. Inspectors from the Berufsgenossenschaft or the state authority want to see that the activity category assignment is justified and that the effect of the measures has been checked.

1. Classify the activities. Record for each zone which activities take place there and assign them to activity category I, II or III under ASR A3.7.
2. Check space and occupancy. Record floor area, number of workstations and peak simultaneous occupancy and compare them with ASR A1.2, with desk sharing based on desks, not headcount.
3. Measure the acoustics. Have the rating level measured at typical working times and the reverberation time measured in the unoccupied room between 250 and 2,000 hertz.
4. Ask the employees. Record disturbance from conversations, phone calls and walkways and the lack of quiet spaces as psychological stress.
5. Set and document measures. Enter structural, technical and organisational measures with an owner and a deadline and check their effect after implementation.

Measures follow the STOP principle under section 4 ArbSchG: technical and structural first (acoustic ceiling, absorbers, screens), then organisational (zones, quiet rules, phone rooms), personal last (such as noise-cancelling headphones as a supplement, never as a substitute). To check the status of the whole office, use the office occupational safety checklist.

Before moving into an open office or switching to desk sharing, an outside view pays off before the lease and furniture order are fixed. Safety Club provides an occupational safety specialist on site plus digital, audit-ready documentation. We answer questions about your space in an initial consultation.

This article is general guidance and does not replace legal advice on individual cases. The current versions of the ArbSchG and ArbStättV, the current Technical Rules for Workplaces and the requirements of your accident insurer and the supervisory authority responsible for your location are authoritative.