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You will find the answer in BS 5395 part 2 but it will not tell you the actual diameter required for a spiral staircase. The standard specifies the clear width required for different applications. For instance spiral staircases serving as the main house staircase would come under category B which requires a clear width of 800mm.
The definition of the clear width is the distance between the outside of the spiral stair centre pole and the inside of the handrail, this in practical terms is the width that you have available to walk up or down the stair. This is a good way of specifying the required size because if you have to escape down it in the event of a fire this width could be critical. Specifying the outside diameter of a spiral staircase does not really define the clear width because different designs and different styles have different sized centre poles and handrails which will in turn have change the amount of clear width.
None of the above really helps the questioner, what he really wants to know is how much area he needs to leave to accommodate a compliant primary spiral staircase in his new house design. The answer is about 2000 mm diameter, I say about because as you now know, without knowing the constructional details of a the specific spiral stair I cannot say for certain. Personally for design purposes I would leave if possible an area 2100mm square this would just about cover most models of spiral staircase that you are likely to buy. In my experience I have not found any modern designs of Category B compliant spiral stairs that are smaller than around 1900mm.
The only real safe way of answering this question is for you to choose your spiral stair model and ask the manufacturer what diameter will comply under BS 5395 part 2 as a main staircase in a dwelling.
The spiral staircase Doctor.
It is difficult to generalise on all manufacturers of kit spiral staircases, although what can be said is that they are all continental and almost all do their own load testing etc. aimed at their own national standards but not specifically for the British Standard. The chances are that there will be something within the British Standard that will not be covered in the Continental equivalent and visa versa. That is not to say that either is wrong just different. Theoretically all us EU communities are attempting to eventually bat on the same wicket, but in the current state of the union that looks less like a priority.
So the questioner has his eye on a nice kit staircase and he knows that if someone claims that it complies with the British Standard then it will be acceptable under the Building Regulations. That is perfectly true but a very difficult claim to make with any adjustable spiral stair kit. The ability to adjust means that the end user can in all probability adjust say the tread rise outside of the British Standard maximum therefore it would not meet the standard. So, why not make the adjustments so that they can only remain within the standards. Yes a good solution, but whose standards, the Italians or the Brits! When you make a kit product to sell on the world markets it has to have built in compromises in an attempt to keep everybody happy as much as possible. If you were to go to a reputable bespoke spiral staircase manufacturer you should be able have a staircase made that will meet all the nuances of the British Standard but you will of course pay for the privilege. Reputable kit spiral stair companies should also be able to advise you on which spiral staircases you can use and how you can use them for specific project to meet the main conditions of the British Standard. It would however be a reckless company who boldly stated that it totally complies with everything in the British Standard, unless the manufacturer has had it independently tested and approved by a qualified body. The heavy costs of this procedure means that no continental manufacturer is ever likely to go through this process just for their British market. The only kit spiral stairs that I know of that have been specifically tested to BS 5395 part 2 are the Klan and Civik ranges. The report runs to 50 pages and even then they can only approve the specific sample submitted which means one specific diameter and one specific floor-to-floor height. The document does however lend credence to a Local Authority approving these particular spiral stair models providing that you check that your specific height and diameter can meet the requirements.
None of the above proves that any other make or model of spiral staircase is not suitable under the conditions of the British Standard, it is just difficult to prove it. As I understand it equivalent European standards should be acceptable in the UK but getting a document from the continental manufacturer that is in a language that is understandable and acceptable to your Building Control department may prove to be another matter.
As always I recommend that you talk to someone 'who knows' who can advise you on your specific project before you go too far. Judging by the number of kit spiral staircases that get approved each year by various Authorities all over the UK you may have less trouble than you think.
The spiral staircase Doctor.
A highly technical question from a deep thinking gentleman.
This gentleman has spotted what the mathematicians amongst can see is a flaw in the geometry of making a helical wooden handrail for variable height kit spiral staircases out of short wooden sections. This is exactly what happens on spiral stairs kits such as the up market Genius range. However the manufacturer is on the case and has an answer for this problem.
Let me first explain the problem. A spiral staircase handrail forms a helix just like the spring on your pogo stick. To form this out of real wood is an expensive process requiring curves in two directions. It goes round in a circle on plan, the circle being the same diameter as the spiral stair. It also has to climb from the bottom to the top stair tread which is the second curve. OK all of this is possible but the helix will vary with every diameter and with every height. Therefore you have to make purpose designed helix for every stair. All kit spiral stairs like the Genius range require you to be able to change the height of spiral stair. Without this variability you would no longer have off the shelf kits, but would have to pay a lot more for a spiral staircase made specifically for your floor-to-floor height and diameter.
There is a further problem with kit spiral stair helical handrails, they are not only difficult and expensive to make, they are also big, awkward and very expensive to transport in one piece. So having made a helical spiral stair handrail the manufacturer cuts it into shorter lengths so that it can be packed in crate and transported. This process also requires the design of a method of rejoining the pieces together.
So the problem is how to make spiral staircase handrails that go round in a circle of a certain diameter but also curve in another direction to allow for various heights. The first curve is easy you just make a set handrails to suit the various diameters that you supply the stairs in, lets say four diameters. So each diameter spiral stair has its own handrail. The second curve is much more difficult. The only real solution is to also make a handrail not only for each diameter but for each millimetre of height of the stair height range. This is practically impossible as it would require the manufacture of thousands of variables. Failure to do this however means that the handrails will climb the spiral stair at a different angle of pitch to the stair treads, so it will get higher or lower in relation to the treads.
So the solution to this problem lies in the way that the handrail sections are joined. Instead of making the join between two handrail sections butt up hard against each other which would fix the angle of the second curve, the clever manufacturer supplies a clear tapered washer that fits between the two sections. By rotating the washer you can vary the angle of pitch a little on each join. This solves the problem, it is not a perfect solution but it works, and if you take your time with the washer adjustment you will achieve as near a perfect result as makes no difference. Unfortunately it does require you to align it by eye and tape measure as it would be nigh on impossible to produce any kind of tables that would help with this. Trust me it does work, I have seen Genius spiral stair handrails that have been assembled by people who were totally oblivious to the function of the tapered washer and just inserted them any which way. The result looked fine even to my highly critical eye. So worry ye not my mathematical friend the circle can be squared, or near enough anyway.
The Spiral Staircase Doctor
This is a Doctor Who Tardis problem, how to get a quart into a pint pot. There are many types of Victorian terraces but the one I am regularly asked about consists of front and back rooms with two bedrooms above and possibly a single storey scullery extension out the back.The staircase goes across the width of the building between the front and back rooms, access to the back sitting room being under the stair landing. In my opinion this design shows just how good the old folk were at getting the best out of a small space. Fortunately they were not hampered by the modern requirement for unnecessary things like bathrooms or kitchens with dishwashers and microwaves.
So a great design for your great grandparents but a nightmare for access to that nice big unused loft space. Unfortunately I have never found a simple answer in providing a loft staircase to this type of property. If there was a simple answer it would have long ago been fashionable and would almost certainly have been adopted by the original Victorian designer. I am always amazed at the number of young people who come to me with the revolutionary idea that they have discovered of buying in a two bedroom terrace and simply making it a three bedroom by using the loft space. Believe me if it were that simple the whole street would already have three bedrooms.
The basic problem is that a loft staircase will require floorspace on the first floor and the only floorspace usually available is found by reducing one of the already small bedrooms. What about putting one stair over the other I hear you cry. That is a good solution but unfortunately access to the loft stair will still require a corridor making in one of the bedrooms to access the foot of the loft stair, so there is nothing to be gained in floor area.
So there is no easy solution and somewhere along the line it is going to cost you space in the existing bedrooms. You may be able to reduce that space by using a space saver stair like the Karina but it will still take up some space and will of course require approval by the Local Authority. A fairly common but expensive solution is to rip the entire room layout apart and end up with a through lounge and a new stair running front to back. You may also be able to convert that stair to a two storey spiral staircase to get access to your new loft room as well. However been warned that You will probably find that the diameter of spiral staircase required by the Regulation people may make this option too large to be workable in the narrow width of your terrace.
I am sorry that I cannot come up with a magic answer, believe me if I could I would be a very rich and happy old man.
The Staircase Doctor
Why have I got a plastic as well as a wooden handrail in my spiral stair kit.
This questioner actually wrote for advice because she had bought from a supplier a Mr Step Gamia Wood spiral staircase with a wooden handrail. When it arrived the crate contained a plastic tube handrail with a wooden handrail as a separate item. Her complaint was that she was paying for two handrails when she only ordered one. Her supplier was not sympathetic saying only that that is the way they are sold.
Although it seems a strange way to do business the supplier was actually right, the Gamia Wood spiral staircase kit is pre boxed with a moplen plastic handrail, the wooden handrail is then sold as an extra add on. In reality the Moplen plastic handrail which looks like a corrugated black plastic land drainage pipe probably costs the manufacturer virtually nothing, so leaving it in the box is a cheaper option than opening it up and repackaging the wooden handrail.
I do agree however that it is not the best way to present a product. Never mind the cost, it can also be very confusing when your installation instructions do not show how to put together the wooden handrail and your box contains a drainage pipe that you spend an hour wondering where to fix it on the spiral stair.
I have on many occasions in the past pointed out to Rintal the Italian manufacturer of the Gamia Wood spiral stair, that customers did not like this situation and were complaining. I never managed to get them to change anything which I think is shame. However to be fair to them the Gamia Wood spiral stair is an entry level kit that is sold at a remarkably cheap price, so maybe the ownership of a bit of spare drainage pipe is a price worth paying if cost is an issue.
The Spiral Stair Doctor
Alternating tread space saving stairs of which the Karina is one have their own rules under part K of the Regulations for England and Wales. They are not allowed at all under Scottish Regs. These rules parts K1.22-24 do not specify a maximum pitch but they are quite restrictive on where and when you can use a space saver stair. Basically they are intended to serve a one bedroomed loft conversion, it can have an associated bathroom but the room itself cannot be a kitchen or a lounge. There are other restrictions but I would need more information on the specific project details in order to advise on the suitability of a space saver stair.
So in conclusion the steepness of a space saving stairs like the Karina are not an issue but lots of other things might be. Seek more advice from someone who knows, or contact your Local Authority Building Control for their opinion on your specific project.
Though I do not know the full circumstances of this staircase it all sounds like a non starter as far as the law is concerned. Alternate tread space saving stairs are not suitable for use as the main access to a flat or any other type of dwelling. Space saving stairs like the Karina Gamia Mini etc. are really only permitted when serving a one bedroom loft conversion, and even then there are other restrictions that might apply.
The problem with using a space saver stair as access to a flat above a shop is really about how you escape in the event of a fire. Anyone renting that flat should at the very least be given a safe escape route in the event of a fire in the shop below. Ideally this should be an external fire escape direct from the flat to the ground outside, or if this is not possible a full internal staircase which is enclosed in a fire protected passageway that goes direct to the outside of the premises.
Space saver stairs are wonderful at giving access in places where space for a stair is at a premium, but I would never recommend their use as a main access to any property. I would advise the questioner to seek advice from their local Building Control Department who will be capable of advising them on the requirements for their specific project.
The Staircase Doctor
In theory yes, in practice it is probably a non starter. There are many reasons why not, not the least that it is too small an area. In practical terms spiral staircases of less than 1200mm in diameter are likely to provide too small a tread width to ascend in comfort, and be nearly impossible to ascend if you are some what portly. In Building Regulation terms you are unlikely to get a compliant spiral staircase of less than 1400mm or 1500mm in diameter.
Small cupboards are also likely to cause problems with access to spiral stairs, this is because there is a possibility that the bottom tread will end up pointing at one of the walls and not your required access point. Spiral staircases have fixed rotation characteristics which means that you can only choose the position of either the bottom or top tread, the position of the other will be where the fixed degree of rotation makes it fall. So small cupboards with walls on at least three sides are not the ideal.
In 1000mm square cupboard you could squeeze in 1000mm diameter spiral but it would touch the walls where it passes them and would not be ideal. Ideally the maximum size spiral stair that you could use is 950mm in diameter, that would be more like a fireman's pole than a spiral stair. Not to mention that there are no modular kit spiral stairs on the market that are available in so small a diameter. This in turn means you would have to go to the more expensive option of having a bespoke spiral stair made for you.
So the conclusion is forget the idea and consider using an alternative tread space saver stair kit. However even these will not fit entirely within the confines of your 1000mm square cupboard, but if you can adapt the walls a little it is your best chance.
The Staircase Doctor.
Modular spiral stair kits are the equivalent of Ikea type flat packs in that they are all pre-boxed ready for sale. This makes huge savings in both manufacturing and transport costs, which in turn reduces the price you pay. In fact typical kits like the Klan spiral stairs retail at less than half the price of typical made-to-measure spiral staircases. There are however limitations, the whole spiral stair design has to allow for the various elements to fit into a transit crate of an acceptable size to transport without increasing transport costs. Full helical handrails manufactured in any material are both expensive to make and extremely difficult and expensive to transport without damage. Imagine a huge curly-wurly taller than yourself and big around, though not particularly heavy it takes up a lot of volume on a lorry and is difficult to stop rolling around.
For the reasons just mentioned, there are no modular kit spiral staircases on the market that have one piece helical wooden handrails. All handrails are made up of sections joined together, each section usually approx 1000mm long, that incidentally being the longest length that you can pack in crate of a standard Euro pallet size.
Most of the cheaper modular kit spiral stairs that are on the market do not actually have wooden handrails at a, but use a flexible PVC, usually with a soft aluminium core and an outer acrylic wood film to match the real wood treads. This allows the sections to be stored straight and then formed on site to suit the required helical shape. There are for their sins even kits on the market that use what I can only describe as a kind of black corrugated plastic land drainage pipe that is supplied in coil. They are certainly cheap and are OK if you do not mind plastic drainage pipe in your living room.
The more expensive modular kit spiral stairs do use real wood in the handrails but this will put the cost up. You have to bear in mind that bent wood is expensive to produce and you cannot have one size fits all, every spiral stair diameter requires a different radius in handrail. Technically a true helical handrail section will need to curve in two directions and one of them will vary depending on the height of the stair. As the heights of kit spiral stairs are adjustable this double curve is not possible to produce in a kit, but the clever manufacturers get over this conundrum usually by using clear tapered washers between each section.
In conclusion, you pays your money and takes your choice. Full wooden helical handrails look superb but are very expensive. Wooden section handrails are not far behind in looks, but do not discount the wood look a likes, if cost is consideration they are not a bad option. Just forget the drainage pipe style.
The Spiral Staircase Doctor
In a way the real question is, do you have the room for a permanent space saver stair on the landing? If the answer is no then a loft ladder or an electric loft ladder is the answer. If the answer is yes then I suppose the next question how much do you want to spend? Less than £.1000.00 on a space saver stairs or around £.2000.00 for an electric loft ladder.
Having decided that you are rich enough to have either, then it really comes down to comfort and ease of usage. Both are quite steep but you will be amazed how comfortable both are to climb. Although you have to remember that you come down an electric loft ladder facing into the ladder, where as space saver stairs are descended face out like any other stairs. On that basis I think space saver stairs win for comfort. However having the electric loft ladder folded up out of the way does save even more space, and do not forget the wow factor when you zing it down to you show your friends your etchings in the loft.
From the installation point of view there is not much to choose, space saver stairs are more complicated to erect and will almost certainly require you to extend your existing loft aperture. However your loft aperture will probably also have to be made bigger for an electric loft ladder, and though they are easier to install electrically operated loft ladders also require an electrical power point nearby in the loft.
If space is at a premium I personally would be quite happy with either a space saver stair or an electric loft ladder it is not really a question of which is better but more which works best in your particular circumstances.
The Stair Doctor