How Many People Can a Container Office Hold? A Space-Planning Guide

The short answer: In considering office space for desk work, one should factor in around 4.5 to 5 square meters of floor space per worker in the working area itself. Moreover, one should also account for space for toilets, meetings, and circulation. A typical office of 40ft in length provides an approximate floor area of 28 square meters but that is reduced once walls have been insulated and lined. Thus, not more than a few people can easily be accommodated in such containers. The greatest mistake is to consider the number of chairs that can be accommodated and forget about space not meant specifically for desks.

Why The Headcount Question Is Harder Than It Looks

Whatever the employer’s needs, it always begins with a headcount: "We need an office for twelve." The math seems easy enough, however, it is a very peculiar type of office. The container is a long, narrow and low space, and adding every layer of insulation reduces its width.

The starting dimensions are standard ones: the interior of a 20ft shipping container is approximately 5.9m long and that of a 40ft one – 12m. The width is around 2.35m in both cases, which allows us to approximate the gross floor area of the container: 14m² and 28m². These are the dimensions of the empty container. Once you add the wall panels and floor covering, the space becomes smaller.

What The Rules Say About Space Per Person

There is no single global rule, and many countries say little about office density. The UK is one of the few that gives a number. The Health and Safety Executive's guidance on workroom space says the empty volume of a room, divided by the number of people who normally work in it, should be at least 11 cubic meters. It also calls that figure a minimum that may be too little if furniture takes up much of the room, and it exempts some small structures where space is necessarily limited, such as kiosks and attendants' shelters.

The interesting part for container offices is that the rule is about volume. That means ceiling height changes how much floor you need.

Finished ceiling height	Floor area needed per person for 11 m³
2.2 m	about 5.0 m²
2.3 m	about 4.8 m²
2.4 m	about 4.6 m² (the figure HSE gives)
3.0 m	about 3.7 m²

A container office often achieves a final height of about 2.2 to 2.4 m according to the type of construction done. Hence, the average per-employee square footage required is about 5 m², which again is out of the ordinary because a standard office with high ceilings would require much less than that. If your office is located outside the UK, you may not apply any similar figures because the local regulations may not cover this issue, but it’s still worthwhile checking out their volume before making the final decision.

The three size bands, and what they mean per person

ZN House organizes its office layout into three different groups; this table also contains one column of arithmetic of our own, which is the area for the floor per head under the condition that the maximum number of people in the band generally fits into the maximum area.

Team size	Floor area	Spaces listed	Area per person at the top of the band
1 to 10 people	18 to 54 m²	Office area, manager's office, toilet	5.4 m²
10 to 50 people	54 to 210 m²	Office area, manager's office, toilet, lounge, restaurant	4.2 m²
Above 50 people	210 to 1,000 m²	Same as above	Headcount not stated for this band

There are two things that are noticeable. Firstly, in those areas, there may be toilets, manager's office and even lounge and restaurant in larger bands. Thus, total space available for desks is not as large as it seems. Secondly, there is little per person workspace as it is only 4.2 square meters per person in a large area for 50 people when compared with the above mentioned figure for workroom.

(One small note on the source material: the product page's text for the middle and top bands refers to "54-210 people" and "210-1000 people", which looks like a slip for the area figures. The headings give the headcounts.)

Where The Floor Space Goes

Seats are only part of it. In a typical container office, floor area is spent on:

• Circulation. In a box 2.1 to 2.2 m wide inside, a desk row and a walkway use up almost the whole width. Two rows of desks facing each other won't fit in a single unit with a usable aisle.
• Toilets. Even one small cubicle takes a few square meters, plus any plumbing wall.
• Meeting space. A meeting room for six is easily 10 to 12 m².
• Partitions. The page notes soundproof partitions in the larger layouts. Good acoustic walls are thicker than thin ones, and thickness costs area.
• Stairs and landings. If you build up, the stair takes floor on every level it serves.

Building Up: The Multi-Story Option

According to ZN House’s engineers, the container office design can go up to 3 stores, making it an excellent way of accommodating many people in a small space. However, this has its own implications for planning and, therefore, it is where layout changes from being an issue in fitting furniture to one relating to construction codes.

Take exits as an example. Under OSHA's exit route rules in the United States, an exit route must support the maximum permitted occupant load for each floor it serves, and a workplace needs two exit routes at minimum, or more if the number of employees, the size of the building, its occupancy or its layout means everyone couldn't leave safely in an emergency. OSHA points to NFPA 101 and the International Fire Code for working out how many are needed. A three-level container office with one external stair is unlikely to satisfy that on its own for a large team. Other countries have their own fire codes with their own numbers.

Additionally, there is a specific structural concern when it comes to connecting containers. In order to effectively connect two containers, the side wall of one container must be opened, which will reduce the amount of steel structural members that are able to carry the load. It is essential to confirm with the supplier how this will be handled and whether the engineering has been approved for the proposed number of levels.

A Worked Example (Illustrative)

This is a made-up scenario to show the arithmetic, not a delivered project. Say a project team of 12 wants a site office made from 40ft units, with a small toilet, a meeting room and a manager's room.

• Each 40ft unit: about 28 m² gross. Three units: about 85 m² gross.
• Allow roughly 10% for wall panels and lining. This is an assumption, so ask your supplier for the real figure. Net: about 76 m².

Need	Working	Area
Open workroom, 12 people	12 x 4.8 m² (2.3 m finished ceiling)	57.6 m²
Toilet	One small cubicle	4 m²
Meeting room	Six seats	12 m²
Manager's room	Single office	9 m²
Total needed		about 83 m²

Three 40-foot units yield approximately 76 square meters of usable space. Thus, the plan falls short by approximately 6 square meters. Potential solutions include using a custom-sized unit, adding an extra level, creating a smaller workspace (not ideal), or reducing the number of workers at one time. An engineer would be able to answer the question in minutes, and knowing the answer before placing an order is far cheaper than finding out after receiving the goods.

Questions To Ask a Supplier

1. What is the finished internal length, width and ceiling height of this unit, not the nominal container size?
2. How many people was this layout designed for, and what area per person does that give?
3. If I join units, how is the opening framed, and who has signed off the engineering?
4. For multi-story layouts: how many exits, what stair arrangement, and which fire code is it designed to?
5. What do the partitions do for sound, and how much floor do they take?
6. Which services (power, water, drainage) does the price include, and which do I arrange on site?
7. What approvals will my local authority want to see before the office can be occupied?

FAQs

Can ten people work in a single 40ft container office?

It might be feasible for a very small number of staff working at a desk, but it is very cramped. Ten persons working 5 m² each require 50 m² of space for their desks, while a single 40-foot shipping container exhibits only 28 m² of total available floor space. Thus, two containers or a 40-foot container used as a desk or meeting space is probably a more viable option.

Can container offices be stacked?

ZN House states that the designs may be up to three levels high. However, whether a specific project can be designed in such way depends on engineering, foundations, and local building and fire codes. Therefore, it is recommended to contact both the supplier and local authority before deciding.

Does a container office need a building permit?

Yes, it’s true in many instances. Especially when it does not move from the place or if there are services connected to it. Each country and status of the unit might make the rules differ. Verify with your local building authority from early stages of the project, before the layout is finalized.

Where to look next

ZN House's container office page shows the layout bands and size options discussed above. If you are weighing different build types, the folding container house and easy assemble house pages describe the transport-friendly options, and the container camp and container dormitory pages cover offices that sit inside larger site layouts.

Sources

• UK Health and Safety Executive, How much space am I entitled to at work?
• US Occupational Safety and Health Administration, 29 CFR 1910.36, Design and construction requirements for exit routes
• ZN House, Container Office solutions page (layout bands and size options)

Disclaimer: This article is general information, not legal, engineering or building-code advice. Space, fire-exit and permit requirements differ by country, region and use, and they change. Confirm what applies to your project with ZN House, a qualified engineer and your local building authority before you order or build.

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