How much office space do I need? The HSE’s 11 Cubic Metre Rule

by Crispin Maby

I have re-written this article since first publishing it in 2014 because at the time I was critical of the vague definition provided by the HSE in one of their regulations.  But 7 years on I have re-read the same regulation and, although I might be wrong,  I think perhaps the wording has changed slightly.  Nevertheless, it is still its not entirely clear and I will explain why later. 

Also, in the light of Covid 19 I’m wondering whether regulation relating to this matter might become policed more strictly or indeed whether they might actually amend it.  If it is amended, I will endeavor to update my article again.

One aspect of office space planning that often gets overlooked is the personal space allowance as stated by the Health and Safety Executive (HSE).  It accounts not only for the floor area taken up by desks, but also the volume of space required per person.  So we have to consider a 3 dimensional aspect rather than just the 2D floor plan.

This is of particular importance to you, the office occupier, because it may well be the determining factor in establishing how many people you can have legally working from your office.  I’ll cover this later, but the point of this article is to explain that even though you might be able to physically fit a given number of desks (and therefore full time workers) into your office space, you might not be permitted to do so.

In a nutshell, the regulation (Regulation 10 of the Workplace Regulations 1992 to be precise) states that you have to allow a minimum of 11 cubic metres of space per person working in the office. Unfortunately though, even though this is a regulation, and therefore we must assume that it is law rather than a recommendation, the information they provide us with is somewhat vague.  The key areas of confusion as far as I’m concerned are that:

1. There are 2 contradictory statements,  one referring to the ‘the number of people who may work in any particular room at any one time’, and the other ‘the number of people normally working in a room‘ .  So which do they mean?   
2. The second vaguery is the wording in the following statement: ‘The figure of 11 cubic metres per person is a minimum and may be insufficient if, for example, much of the room is taken up by furniture etc‘.  What do they mean by ‘much of the room’, and what sort of furniture are they talking about?  Do they mean cupboards and large solid objects, or are they also including the desks and chairs that we sit on?

Perhaps its just badly written or poorly thought through, both of  which would be unforgivable considering this is a legal obligation for us to adhere to,  so maybe we should give them the benefit of doubt and assume that they realise it is simply too difficult and far reaching to cover every scenario and instead they are giving us guidance to which we need to apply a common sense approach.

For your own office, you will have to make your own judgement on this as I’m simply pointing out what is being said and what different interpretations mean you might, or might not be able to do.

Firstly to item 1 above – ‘the number of people who may work in any particular room at any one time’, and  ‘the number of people normally working in a room‘.    If you take the first statement literally, and you have, for example, 110 cubic m of clear air volume, then it means that you can only have 10 people seated at a desk at any one time. But if you take the second statement to be true, then perhaps you can have far more people working there on occasions, as long as there are normally no more than 10 people. But in this scenario, who decides what is normal and could it simply mean more than 50% of the time?  Also, specifically in relation to the 11 cubic metre rule, nowhere does it state how many desks you can have in relation to the number of people. So, hypothetically, in relation to both statements, you could have (as long as the space permits) a far greater number of desks than you would either a) have people working at any one time or b) normally working in the room. I suppose it could be argued that if the desks are there, it must then be assumed they could all be occupied and therefore encouraging the breaching of the rules.  My personal opinion on this would be that common sense must prevail here. Firstly, volume permitting or not, the 2 dimensional layout of the office has to be such that it allows for safe and practical working and this is covered (albeit extremely briefly) in the regulation.  But as long as it can be done in a sensible manner, then there is no reason why you shouldn’t maximise your layout to include extra desks as long as you take a common sense approach and risk assessment and ensure that your principles are adhered to.  After all, even in a busy office with full desk occupancy of full-time desk workers,  how often is it that everyone is at their desk (or indeed in the same room) at the same time?  People go for meetings internally or externally, people take different lunch and coffee breaks, people start and finish work at different times and so on, so even in these environments its very rare that every desk is occupied simultaneously.    

And on item 2 above,  we need to be sensible about this, and I don’t think anyone can be expected to start calculating how much volume each desk and chair takes up, besides which there is air flowing beneath and around them, so personally I would only be concerned about the impact of large cupboards and other very bulky items.  

Finally, before we move on, I should be clear that the rule applies only to workrooms and not meeting & lecture rooms (assuming they are used as such and not as full time work rooms).

So, onto some examples to help make everything a little clearer.  Given how unclear the regulation is as I outlined above,  I’ve decided to use the worst case scenario for my examples, that being the assumption that each desk must have an average 11 cubic metres rather than each person (therefore the assumption that each desk is occupied all the time).

In my experience,  the typical modern office has a ceiling height between 2.4 metres and 2.7 metres, so let’s go with 2.5m as a good compromise.  Firstly we need to calculate the volume of the room by multiplying the floor area by the ceiling height and then dividing it by 11. The resulting sum will give us the maximum number of people we’re allowed to fit into this space (if we have cupboards we will have to make a deduction for this before the division).   How does this look in practice?  Below I have done 2 CAD drawings (Figures 1 and 2), figure 1 showing an open plan office packed with as many 1200mm by 800mm desks (these are the smallest of the regular sized desks generally used in offices) that will physically fit, and figure 2 with the same office showing how many desks we would have to remove in order to achieve the capacity we are actually allowed.  To save you counting, there are 104 desks in figure 1, and this is reduced to just 58 in figure 2 – a reduction of 44% no less!

Ok, you say, but that’s an unrealistic office layout. We’d never have so many people in one area. We’d have other things like storage cupboards, reception counters, larger desks, meeting areas, breakout areas and probably also additional rooms.  Well I have to tell you that I’ve seen offices just like this (figure 1) and although perhaps an extreme example, the rule applies no matter how large or small the office is; – for example, we might not be looking at the main office, but a smaller room within the building into which you want to get as many desks as possible because your reception, meeting rooms and the like are in different parts of the building.  So the sake of continuity and simply to demonstrate a point, we’ll stick with the original plan for the time being and I’ll start introducing other factors.  Let’s assume that we’re now down to our 58 desks and we’re looking to fill the rest of the space as best we can with other furniture.   In figure 3 I have inserted 36 tall free-standing cupboards (let’s say 2m high) a couple of meeting areas, reception counter and waiting area.  The cupboards now have an impact on the permitted desk volume because I have had to factor in that each one has a volume of 1 cubic metre, and as a result it has reduced our room volume somewhat and in turn we’ve had to take out 2 more desks to compensate.

All very good, but it’s all very open plan and maybe we need some private space with sound and visual privacy, so figure 4 again shows the same office but this time with a large partitioned meeting room and 2 cellular offices.  Because we’ve introduced partition walls, the areas within these new rooms can no longer be considered to be part of the open plan area and the cubic capacity of the new and smaller open plan area reduces dramatically as a result. I have had to remove yet another 20 desks of the remaining 56, giving us now a mere 36 desks (a further reduction of 35%).  I must be honest, I don’t know whether I’m allowed to include the corridor as part of the open plan space (HSE guidance is not specific about these issues) but for the benefit of doubt I have not.  If it is permissible, then we would have been able to add back in a couple of desks.

So there you have it.   If the ceiling was higher, then we could have taken this into account and increased the volume and therefore quantity of desks, but this applies only up to 3m – there above we have to ignore any further height advantage.

How does this relate to typical office capacities?

If you are interested, the plans I have drawn in figures 1 to 4 have an overall footprint of 259 square metres (2,787 square feet).  When companies are looking for a new office, a very general but typical rule of thumb is that on average you allow 100 square feet per person (this takes into account the entire office, including meeting rooms, breakout areas etc). If you follow this rule of thumb, then on average, regardless of the ceiling height, the 11 cubic metre rule becomes far less relevant because in this example, you would actually only be looking to get 27 people/desks into the office and my worst case scenario allowed for 36 desks.  Be careful though, because it is all about the capacity of desks within a specific room or area and what this does show is that it’s unlikely that you would be able to cram any particular room just with desks and no other furniture or spare space.

______________________________________________________________________________

What defines an Ergonomic Office Chair?

It seems that every manufacturer and supplier in the office seating business offers Ergonomic chairs, but in the context of office chairs, what does ‘ergonomic’ actually mean?  Generally, not a lot, because there is no official definition so it becomes a matter of opinion. Hypothetically, anything that is designed for use in the workplace and has some sort of efficiency or comfort feature qualifies. For example, a really basic chair with a swivel base but with absolutely no adjustments can arguably be classified as ergonomic because the swivel feature allows the user more freedom of movement than a chair on four static legs.  But would you really consider this to be an appropriate level of functionality for a task chair (desk chair) that promotes wellbeing and efficiency?  Almost certainly not.

So it’s probably best to disregard the ‘ergonomic’ label completely and focus on the features and functionality of different models and brands of chairs.  Create your own definition of ergonomic if you like and decide what fits specifically your needs.  Different types of chairs serve different purposes whereby varying degrees of comfort, functionality and adjustability become of greater or lesser importance.  Considerations for sitting at a desk (and probably working with a computer keyboard or laptop) for 8 hours a day are different to those for a meeting room chair that may only be sat in for brief periods of time.  Furthermore, for each type of chair and task performed, individual users needs should be taken into account – we are all different –  we work differently, we sit differently, we’re different weights, shapes and sizes,  some of us have back and posture problems,  and we like to do things in different ways, so, one size most certainly doesn’t fit all when it comes to office chairs.

Office seating can probably be broken down into 3 or 4 different task related categories.

1. Desk Seating
2. Hot Desking/Drop-in
3. Meeting
4. Relaxation/Informal

Desk Chairs/Task Chairs

The most important category, by far, is that of desk chairs or task chairs as they are often known.  This is where getting the right fit and the right level of functionality and comfort and adjustability can have a profound affect on the user’s concentration, productivity, comfort and health.  If an office chair is defined as ergonomic, this is usually the main purpose/task for which it was designed.  Let’s first look at the main issues, and then at the design features that are there to address these.

Lumbar Support

Our backs need supporting, particularly so in the lower lumbar region but not overlooking the mid and upper regions.  A one-design-fits-all is generally not possible because we are all different heights, weights and shapes, but a really well designed chair can certainly address the needs of many and possibly the majority. Support in the lumbar area can be achieved in many ways. One is to shape the backrest to ‘hug’ and hold up the lumbar area of the spine, and for the backrest itself to be adjustable in height so that the lumbar support is positioned correctly for the individual user.  Another is to have an adjustable lumbar support which can move up or down a static backrest to achieve the same result.  In both cases, the lumbar region also needs to be adjustable in shape and tautness in order to fit the user snuggly.  So far so good, but the real challenge comes with user habits, particularly when working at a desk.  To help explain, we will quickly look at traditional executive chairs which had a fixed angle between the seat and the backrest. If you wanted to lean back, the whole chair would tilt backwards – just like a rocking chair – but the angle between the seat pad and the backrest would remain the same – i.e. the front edge of the seat would simply tilt upwards, and the whole chair backwards. More about this later because this kind of mechanism is still in use today – unsurprisingly it’s called ’tilt mechanism’ and it is not uncommon for people to mistake this with more appropriate designs for desk working.  I’ve seen it a number of times  – desk-bound office staff being given executive style tilt-mechanism chairs on the incorrect assumption that they look nice and comfy, they’re designed for executives so they must be a step up from a standard desk chair.  But this is not correct and here’s why:

With typical modern desk chairs, simple or complex, cheap or expensive, the backrest and the seat pad can normally move independently of one another. The design and functionality varies considerably, but in it’s most simple form, the user can recline the backrest whilst leaving the seat pad in the same position.  The concept is considered very important.  The body needs to move or change position regularly and sitting in the same position for prolonged periods of time, no matter how well supported it is, is generally considered not good.  The advice is to change your seating position from upright to various degrees of reclined regularly throughout your working day.  So, the moving backrest is good for this but the problem occurs when the user fixes it in a reclined position, and then sits forward to do computer  keyboard work. Their spine loses contact with the backrest and all benefits of the lumbar support are lost.  The solution is to have a mechanism that allows the backrest to ‘free-flow’ and stay in contact with the user’s back regardless as to whether they are sitting forward or reclined. These come in various types, designs and levels of sophistication and, needless to say, varying degrees of effectiveness:

Permanent Contact Back:  This is the simplest type.  The backrest is set in free-motion and the user tightens or loosens a spring  which adjusts the force required to move it (backrest) when leaning back on it.  Whether sitting back or forward, the backrest is always in contact with their body.

Synchronous / Synchro Mechanism:  This is similar to the above, but in addition the seat pad is synchronized with the backrest;  when the backrest is reclined, the seat pad tilts upwards and backwards to a much lesser extent, but sufficient to prevent the angle between the users upper and lower body becoming too flat/open.  I know I said earlier to ignore the term ‘ergonomic’, but I think it is fair to say that the pundits of our industry would generally consider a synchronous or similar mechanism being the minimum defining characteristic of an ergonomic task chair.  Certainly that would be my view if I was to be asked for a definition.  It’s very important to add that one synchro mechanism isn’t necessarily the same as, or as good as, another.  Some are very basic and some very sophisticated and it is probably reasonable to say even that some don’t necessarily work particularly well or allow the user an optimal seating position, but generally speaking (quality aside because this article is not about how sturdy or well built something is) even the most basic are going to offer at least some benefit over those without.

For all their benefits, synchro mechanisms are not without issues, some operational user related and some design related.  Many, or perhaps I should go as far as to say most of these chairs (particularly the lower cost ones) have a locking facility whereby the user can recline the backrest and lock it off in a position of their choice.  But if you do that, it becomes a basic chair and all the benefits of permanent back support are lost.  This is completely at odds with the design concept but nonetheless it is there. If you choose to spend upwards of £200 (probably the minimum you will pay for an entry level chair of this sort) then you should also make sure to educate your staff about the advantages of such a chair and provide at least very basic training on how to set it up and use it  – so that they do use it properly.  Other manufacturers have overcome this by removing the locking feature so that the user is forced to use the chair correctly.  This is good, but make sure that you test the chair before you buy it with people of different sizes and weights. Sometimes the locking feature is there because the weighting system (either a manual spring tension that the user adjusts to suit their own body weight or an automatic body-weight adjustment) will be ok for people of average heights and weights, but may be too weak for taller-heavier people meaning that they will constantly drift backwards away from the upright position, or too strong for smaller lighter people meaning that they will be forced forward into an uncomfortable vertical or over vertical position.

Another issue with these chairs is that in the reclined position, many will shift the user’s shoulders backwards so far so that their hands are unable to reach the desk or keyboard they are working at. Some manufacturers have overcome this by allowing the user to restrict how far they wish to recline (e.g. only far enough back so that they can still reach their keyboard) whilst enabling the chair to free-float anywhere in between. A company called Grammer Office some 25 years ago took the free-moving seat and backrest concept even further and came up with a unique mechanism they called Glide-Tec.  When I visited their factory in Germany 15 years ago, they told me that their parent company was a manufacturer of automotive seat components and their products were incorporated in one form or another into the seats of most cars world-wide. Then they were appointed to design and manufacture reclining seats for the high speed German trains and came up with a design so good that they started making cinema seating and office chairs with the same type of motion. Basically, it’s like the synchronous mechanism, but instead of the seat tilting upwards and backwards, it slides forwards and allows for the opening out of the body angle whilst only shifting the shoulder position a small amount, thus allowing the hands to stay pretty much in the same position on the desk regardless of whether sitting upright or reclined.  In short, to get the same open body angle as a synchronous chair, the backrest only has to recline a fraction of the distance.  My local cinema has this type of seating, and mighty comfortable they are too. And the last time I flew on an Airbus 380 it also had this style seat and the amazing thing was that not only were they really comfortable, but it meant that when the person in front of me reclined their seat, I still had plenty of leg space.  I have no idea whether either the cinema or aeroplane seats were the products of this manufacturer or another, but most definitely they are the same or similar design.  Back to the Glide-Tec office chairs, these have been part of our product portfolio for years but the manufacturer was bought out and the new owner, in my opinion, has not done much to promote or further  develop what was, and still is, a great chair.  Yes, they were pretty expensive, and yes, they’re not perfect and probably need updating, but everyone I know who has had one and commented on it only had very positive things to say.  Most described  it as the most comfortable office chair they’ve ever used.

Shoulder & Neck Support

Having addressed the back support and seat motion, the next most important thing is armrests.  Its a great mistake having fixed height armrests on a task chair, or indeed no armrests at all.  Fixed height are probably right for a very small proportion of users, but, as said before, we’re all different different sizes so we need adjustability.  Armrests are important because, set and used correctly, they are likely to considerably reduce neck and shoulder fatigue and strain.  They should be adjustable in height so that the user can rest their elbows and part of their forearms on them whilst typing. They also need to be adjustable in a forwards and backwards direction so that the user can get as close as they need to the desk (if the armrests happen to be at the same height as the worktop – as is usually the case – then they may prevent the user getting close enough to their computer keyboard or laptop unless they can be slid backwards).  Width adjustment is important too.  A larger wider person may need them set far apart, where as a smaller slighter person will need them pulled in much closer to them.  Perhaps of lesser importance is the ability to swivel them at an angle, and, of course, it is always good if they are comfortable so soft padded tops are far preferable to hard moulded plastic.

Other features and considerations

This article is not intended to be the definitive guide, and certainly not to list and describe every conceivable feature, but here are a few other common features found on so called ergonomic chairs.

Seat slide: People with long legs theoretically need deeper seats so that more of the underside of their thighs are supported whilst sitting.  It is generally uneconomical to produce lots of different sizes of seat pads, so most manufacturers make just one size (to suit the majority) and some will then offer the option of a sliding seat pad which can simply be slid forwards by the user to bring the front edge closer to the underside of their knees.  A useful feature to have but it is a compromise because when slid forward it leaves a gap at the back (between the back of the seat pad and bottom of the backrest).

Headrest: As the name suggests, intended to provide support for the head, and therefore neck. They can be beneficial but only if really well designed and in my opinion, more often than not they serve little or no purpose.  Very often, particularly on the lower cost chairs, these are just a poorly thought through ‘add-ons’ which don’t give the head and neck the support they are intended for.  To work properly for the majority, they need lots of adjustment (height and depth/fore-aft) so as to suit people of different heights. But even with this degree of adjustability, most users will need a different setting whilst sitting upright to that when sitting in a reclined position. So in general, for users of synchro chairs, even if they can find a suitable setting, it will only be of proper benefit whilst sitting in a certain position.  A few of the more advanced chairs have clever designs that allow the headrest to automatically adjust in position in relation to the backrest whilst shifting from the upright to reclined position, but these are few and far between.

Negative Incline Seat:  I’ve never been sure of the purpose of this although I have tried it and personally found it extremely uncomfortable.  Needless to say a few chairs offer this adjustment and clearly it is of benefit to certain users.  Basically, the seat pad can be tilted forwards so that you are sitting in a forward inclined position.

Hot Desking Chairs

Do we need a high level of ergonomics for hot-desking?  The answer depends on how long people are likely to sit at the desk.  If your users simply pop-into the office from time to time and need a desk or work surface to use for a relatively short period of time, then the answer is no, the chair need not have bundles of adjustability and expensive mechanisms. But if hot desking in your office means that staff come in to work from a desk for a few hours at a time, then the answer is yes, the chair needs to have the same attributes you consider necessary for permanent desk workers.

Executive Chairs

I mentioned this earlier in this article and said I would come back to it.  Traditionally, executive chairs were bigger and wider with taller backs and generally grander looking and usually upholstered in leather. But more often than not, they had a simple tilting mechanism so that the whole chair can rock back and forth, but where the relationship between the seat and the backrest remains constant – i.e. they are at a fixed angle.  Whilst office staff were starting to use task chairs with synchro or adjustable back-rake chairs, the company directors continued to use tilt-mechanism chairs on the basis that they would spend less time sitting at the desk, and when they did they would generally be sitting back and talking or listening or dictating letters to their secretaries.  Today it’s different.  Everyone uses a computer – even senior executives –  so if your senior people spend time at their desks using one, and it is considered necessary to give them a superior chair to everyone else in the office, then a modern executive chair with an ergonomic mechanism would be far more appropriate.

Meeting and Boardroom Chairs

For most meeting rooms and boardrooms, anything goes.  People attending meetings tend to sit back in their chairs with the chair pushed further away from the edge of the table than they would when  working from a desk.  In most cases there’s no real need for ergonomics – a basic static chair often suffices.  Of course, there’s no harm in having movement and adjustability but its generally nice to have  rather than a necessity.   As such, meeting chairs come in all manner of types, from static four legged stacking chairs, to cantilever style, swivel with tilt control, high backed executive chairs and fully loaded synchro chairs.

______________________________________________________________________________

Be careful with your choice of interior wall paint colour

At Octopus we decorate a lot of office interiors, usually in brilliant white, magnolia, off-whites such as timeless or RAL 9010,  various shades of grey or really bold accent colours to meet customers’ specific tastes or to match company colours. But until now, never have we been asked to use Natrual Taupe.

A customer of ours recently instructed us to decorate their London office walls in Dulux Natural Taupe 4. They had already purchased a sample pot and painted a small patch of wall just to be sure, and it came out just as they expected – a slightly off-white pale beige appearance, exactly what they were after.  My decotators set about painting the entire office and it was only when I went in to check on progress a couple of days later, after they had already completed 2 full coats, that I suspected that perhaps this wasn’t the colour our customer was expecting.  It was, most definitely, a pale pink!  This was not just my opinion but that too of everyone else who subsequently looked at it. Interestingly, I first saw it at 6am on a winter’s morning under artificial office lighting, and as daylight began filling the space, it started to look less pink, but one lesser or greater shade of pink or another it remained regardless of light levels in the office.

My first reaction was mild panic. We were fitting the new carpets the following day and having the new desks and chairs installed a day after that.  If we had to re-decotate the office it could be a complete disaster.  Had we ordered the wrong paint? Had our supplier mixed the wrong colour by mistake or was their paint mixing machine faulty?  I rushed down to a different supplier and got them to mix a small sample pot (I wasn’t going to risk going to our regular supplier and getting them to mix another one just in case their machine was faulty and gave us an identical repeat of the wrong colour), and I also took away an official Dulux colour card. To my relief, the new paint matched exactly, as did the colour card.  So, as it turned out, a paint colour that appeared almost white on a small test patch and sample card, was pink when applied to a large wall area.

To test this further, I collected a handful of colour cards from Homebase whilst doing my weekend supermarket shop at Sainsbury’s next door, taking a selection from the ‘browns’ of which Natural Taupe 4 was one, and another selection from the neutrals/greys.  Outside in the car park in natural daylight and held up against my white car, all of the palest brown colours of each range did indeed look slightly pink.

The result:  After the carpets and furniture were fitted, we had to put down full carpet protection and dust covers everywhere, mask up and start again in a different colour in ultra quick time. We got paid for it as our customer acknowledged that it was not our error, but we would rather have not had to go through this for our own sake as well as our customer’s as it involved a lot of extra effort and very tight & unexpected deadlines.

The lesson:  The lightest shades of brown can and do look pink. The greater the amount of daylight, the lesser the effect. The lower the level of natural daylight and the warmer the artificial lighting, the deeper the shade of pink becomes.  Other factors that can effect the appearance are the texture of the walls and the type of paint. A flat matt compared with a silk or eggshell in exactly the same colour will look different due to the amount of light reflection.

Conclusion:  If it’s your home, experiment by starting small and expanding to the whole area if it looks ok. If it’s your office, play it safe and go white or as neutral as possible (or very bold with accent walls if you dare!), but don’t take the chance with pale colours over large areas unless you’re absolutely sure.  If you get it wrong at home, it’s probably a minor inconvenience. If you get it wrong in the office, you might be preventing your business from functioning properly until you reslove the problem.