The creation and installation of stairs can seem like a daunting task at first when faced with all of the different terminology and components. Whilst it is true that there are many critical elements to consider, as well as regulations that govern the allowable tolerances, when broken down step by step, the total process is actually very straightforward. There are a variety of different stair construction styles, as well as a plethora of different shapes and sizes with numerous finishes and optional components. That being said, the calculations required, and general installation procedures are applicable to all staircases. As such, we will begin by looking at how stairs are measured and calculated. We will then look at how these measurements can be used to create two of the most common styles of internal residential straight flight staircases. Once we understand how the different styles are created, we will look briefly at a good handful of the most common shapes and variations that are used in modern residential construction, highlighting the key considerations and variations during installation.

Calculating the pertinent measurements

Regardless of the style of stringer that is being employed, the fundamental calculations and marking out procedures remain the same. The first step is to determine the vertical distance from the lower to upper floor, in order to establish the height of the staircase and the number of steps within it. The critical measurement here is taken from the finished floor to the finished floor. In most instances this will be from the top of the screed/floorboards below, up to the top of the floorboards above. For this example, the height from f/f to f/f is 2600mm, which falls within the typical range for modern residential properties.

To determine the number of steps that we require, we can divide this height (2600mm) by 200mm - a common rise height that is considered ideal and falls comfortably within regulation rise parameters (150mm-220mm). In this instance, we require 13 equal steps each with a 200mm rise. If the height is not perfectly divisible by 200mm, we can alter the calculation in order to return the value of an exact rise height based on the required number of steps. For example, if the exact height between the two finished floors was a random number like 2673mm, we still divide this number by 200mm to approximate the number of steps required. 2673mm divided by 200mm is 13.365 - we can’t have .365 of a step, so we round down to the closest whole number - 13. If we then divide 2673mm by 13, we’re returned with a value of 205.6mm as a height for each rise. This value falls within the allowable range, and so we can comfortably proceed. If the resulting value ever falls outside of the allowable range, the number of steps can be increased/decreased to change the value of the rise until it is suitable.

We now have the number of steps and their rise required for the total rise of the staircase - 13 steps in total. 12 of these steps are full treads within the staircase, with the last riser and nosing at the top of the staircase being counted as the 13th step. We can now calculate the going of each step - the measured distance between the front of each riser to the next. To do this, we must utilise the formula 2R+G (2 x rise + 1 going) to find a suitable value that falls within the parameters of 550mm and 700mm. Any resulting value that falls within this range indicates with a reasonable degree of accuracy that the staircase is of a suitable pitch - importantly at a maximum pitch of 42 degrees. We can work backwards with this formula to approximate the amount of going that we can play with. 2R in this instance is 400mm, leaving us with an allowance for the going being between 150mm up to 300mm. As mentioned earlier, other regulations state that the going of each tread must be between 220mm and 300mm. We can therefore select any value that falls within the allowable range of both parameters, in this case any value between 220mm and 300mm. This value as a going distance will result in a staircase that is close to, if not under the 42-degree maximum pitch limit.

The cumulative value of all of the goings determines the total run of the stairs - the horizontal distance that the flight will occupy. If space is limited, it's advisable to attempt to minimise the individual going value to reduce the overall run of the staircase. In this instance, we’ll try to limit the run of the staircase by sticking to the lower end of the parameters, selecting 220mm as our going. Using a trigonometry calculator, we can enter both the selected rise and going values in order to check the exact pitch of the staircase. In this instance, the resulting pitch of the staircase is actually 42.274 degrees, which is slightly over the maximum pitch allowance. To rectify this issue, we can adjust the value of the going in increments of millimetres within the calculation until the pitch falls within the allowable parameters. In doing so, we end up with a rise of 200mm and a going of 223mm, resulting in a pitch of 41.888 degrees. All three of these values fall within the allowable ranges.

Stepping out using these values, we see that we have 12 equal goings of 223mm, and 13 equal rises of 200mm, with a pitch of 41.888 degrees. The illustration more clearly displays the 13 equal vertical rise increments at 200mm each, from the top of the finished floor below to the top of the finished floor above. We can more easily see here how the top step, still an increment of our rise, isn't necessarily a step within our stringer, and is instead sometimes formed around the structural opening beam. This will come into play and be explained in more detail later.

If we add in the thickness of the treads and risers (22mm and 12mm respectively in this instance) backwards from our stepping out, we can more clearly see how the staircase will come together. The distance from the top tread to the nosing and top of the finished floor is the same rise as all of the other steps, with the flooring and the treads being the same thickness at 22mm. A tolerance gap of around 10mm is allowed for between the back of the top riser and the front of the structural opening beam. Measuring horizontally from the front of the bottom riser to the back of the top riser (plus the 10mm tolerance), we have a total stair going, or run, of 2698mm. Bear in mind that this measurement doesn't account for any extra projections that may be involved with closed stringer flights, but simply measures the total going of the steps themselves.

With the information of how to calculate the critical measurements of a staircase, we can now look at how these figures are used to set out stair stringers - the structural components of a staircase that carry the treads and risers up to the structural opening above. There are two primary types of stringers - cut/open stringers, and closed stringers. Though less common in UK residential construction, cut stringers are easier to understand in concept, being simpler in their construction. We will first look at how cut stringers are marked out and installed - in order to reinforce the information that we’ve just learned. After we’ve looked at cut stringers, we can take a look at closed stringers, which are slightly more complex, though also far more common in the UK.

Cut stringers

Cut stringers are a style of stair construction that utilizes several cut timber stringers as the structural and load bearing components of the stairs and is predominantly suited to US timber frame construction. These stairs still consist of all the same components that we’ve already looked at, with a simpler stringer approach. Whereas closed stringers are routed to enable the treads and risers to be wedged within them, cut stringers, also known as open stringers, are cut from wide timber boards, and facilitate the treads and risers to sit on top of them.

Aside from offering the opportunity for a different finished aesthetic, cut stringers are also more accessible in terms of their layout and creation, enabling them to be cut on site with relative ease. When considering that these stringers are cut from wide 2” boards, typically 10”-12” timbers, these components can be cut and installed during the framing stage, streamlining the process, and eliminating any lead time required for outside staircase manufacture. What’s more, the treads and risers, as well as the cut stringers, are all typically capped at a later date with finished materials during the second fix stage. This means that we can install a functional staircase early in the framing stage, without having to worry about any significant damage occurring to the staircase.

The first step in the installation of a cut stringer staircase is the marking out of the stringer. This process is very much the same as the marking out of closed stringers, with the difference being the underside of the treads and back face of the risers is our cut line, as both of the components sit on the stringer as opposed to being routed into it.

Following the procedure that we have just looked at, the rise and going for the stairs is calculated based on the total rise requirements for the staircase. Using a steel square or tread gauge, the stringer can be set out on the timber. These timbers are regular structural 2” timbers, with a depth that is suitable for the layout of the stringers. The timber should be deep enough that the backing at the minimum depth is at least 90mm thick, to maintain stability within the stringer. The distance of the going and rise can be aligned on the edge of the timber with steel square, as can be seen in the illustration. Stair gauges can be attached to the square to set these measurements, allowing for repeated marking. It is important to use straight timbers here, though the slight crown that will be present should be facing up. Starting from the bottom of the timber, each step can be marked out until the desired number of steps is achieved. In most instances for cut stringers, the top of the stringer sits against some form of apron/retainer at the structural opening, with the step up from the top of the stringer to the finished floor forming the top step. As such, the number of steps that are marked out on the cut stringer will be one less than the total amount of steps required for the calculated rise increments.

In this instance, the total amount of steps that will be marked out on the stringer is 12, as the total amount of steps required is 13, with the transition from the top of the stringer to the next floor forming the 13th step. At the bottom of the stringer, the thickness of a tread must be cut off, parallel to the horizontal tread plane. This accounts for the thickness of tread that will be added again, so that the rise from the finished floor upon which the stringer sits, to the top of the tread, is consistent with the rise of all of the other treads. A 4”x2” notch is then often cut into the bottom of the stringer, as seen in the illustration - the purpose of this will become clear shortly.

Moving up to the top of the stringer, the going is marked out to form the last step within the stringer, at which point the stringer is terminated parallel to the direction of the rise. A similar notch can also be cut to fit over a 2” timber, as we’ll see shortly. Alternatively, a saw kerf can be made in the top of the stringer relative to the position of a supporting hanger, so that some physical restraint can be installed.

Alternatively, sometimes the risers are back bevelled, creating a more unique aesthetic, as well as functionally providing additional tread depth without increasing the going of the stairs. This is achieved by angling the rise markings backwards about an inch at the bottom, once the initial layout has been performed. From there, the stringer can be cut, and the treads and risers are installed as normal. Keep in mind though that by bevelling the risers, the depth of the backing of the stringer is reduced at the minimum point, possibly requiring a deeper timber for use as the stringer. If the risers are bevelled, then the additional distance of the treads needs to be added to the length of the top marked tread, to allow the very top riser enough room to be bevelled backwards, without disrupting the consistent layout of the treads.

Once the stringer is marked out, it can be cut and turned into a template to mark the other stringers, in a similar fashion to how we create a template for joists and rafters. The number of stringers required depends on the width of the staircase. Obviously, we need a stringer on both outside edges of the staircase, with as many stringers in between as required so that they do not sit at more than 16”/400mm centres. A common 850mm width staircase is the maximum size for 3 stringers spaced at 400mm centres. For any staircase wider than 850mm, 4 stringers must be used, with the middle 2 being spaced evenly between the two outer stringers.

With all of the stringers cut, the installation can begin. The first step is to prepare the apron/bulkhead for the installation of the top of the stringers. In this instance, the stringers will be resting against and fixed into the top of the structural stud that also support the structural opening. The 200mm deep joist is not deep enough to provide a full bearing for the top of the stringer, and so additional material must be installed to receive the top of the stringer. In the first example, a plywood apron is fixed to the face of the studwork, deep enough to reach from the top of the opening to the bottom of the top stringer cut. This plywood apron supports the top of the stringers, as well as providing a suitable fixing for the joist hangers that are also employed. This method is utilised in conjunction with the saw cut that is made in the top of the stringer, with the stringer sliding around the joist hanger. This provides additional stability to the structure. Alternatively, specialist angled hangers can be included, though this requirement is typically specified on the drawing. In the second example, a 4”x2” timber is fixed along the face of the studwork at the correct height for the notch at the top of the stringers to fit over it. This supports the top of the stringers and provides an additional fixing.

At the bottom of the staircase, the stringers sit over another 4”x2” timber that is fixed to the finished floor. This provides both an additional solid timber fixing, as well as physically retaining the stringers so that they are unable to move outwards over time.

As the stringers are installed, they are fixed into place top and bottom. If the staircase runs parallel to a wall as most typically do, the inside stranger can also be fixed to the studs, providing additional strength and stability to the staircase. Once all of the stringers are situated, the treads and risers can be cut and installed. The treads and risers are installed in sequence from the bottom upwards. The risers sit on top of the treads and reach the top edge of the stringer cut out. The tread above them then sits on the stringer, with the front edge of the tread coming out to meet the outside edge of the riser. This pattern continues all the way up to the top of the stairs, with the finished floor extending to the outside edge of the top riser. With all of the treads and risers installed, the first stage of the staircase installation is complete. After plastering during the second fix stage, trims, decorative stringer capping, and tread and riser capping are installed alongside the other second fix components.

Whilst we've looked at a straight flight of stairs in this example, the premise and implementation of the cut stringers into other styles of staircase is straightforward, providing that the overarching steps are followed.

Closed Stringers

Closed stringers are a type of stair construction that is far more common in the UK than cut stringers. All of the same layout principles that we’ve looked at with the cut stringers can be applied here with the closed stringer. Whereas the treads and risers are sat on top of the supporting cut stringers, closed stringers are wide timber that extend above and below the treads and risers, with routed slots that house them. The treads and risers’ slot into these housings and are wedged in place in combination with glue and sometimes screws. Due to the added complexity of their construction, they are often manufactured off site, and delivered to site in partially assembled sections, ready for installation within the property. The benefits of this include the minimisation of calculating and cutting that has to be done on site, as well as allowing for refined materials to be employed. Most cut stringers are capped during the second fix stage with higher quality finished materials, whereas the routed closed stringers are already made of fine quality materials. That being said, they must be covered down and protected to a further extent than the cut stringer variety. Without further ado, here is the basic procedure and pertinent points behind the installation of a straight flight closed stringer staircase.

Here we can see a through section of the first floor - 22mm flooring sat on top of a 195mm (8”) joist, with 15mm of plasterboard and skim below to form the ceiling.

As with the previous explanation, the height between the two finished floor surfaces (top of screed and top of floorboard) is 2.6m. To begin, we’ll use the familiar procedure to determine the number of steps, rise height, and tread depth. Once again, the total rise required of the staircase is perfectly divisible by 200mm, resulting in 13 rises. Using the formula 2R+G (2 x rise + 1 going) and adjusting the going incrementally until the pitch of the stairs is acceptable results in a rise of 200mm and going of 223mm, resulting in a pitch of 41.888 degrees.

Stepping out using these new values, we see that we have 12 equal goings of 223mm, and 13 equal rises of 200mm, with a pitch of 41.888 degrees. With all of the rises and goings drawn out we can now also see the total rise and total going illustrated more clearly. The total rise is the distance from the finished floor to the finished floor, with the total going being the horizontal distance from the front of the first riser to the back of the last riser. The steps are marked out onto the stringer in the same fashion as with a cut stringer, though they are located more centrally within the stringer, typically with around 50mm above the nosing of the steps, parallel to the pitch line of the staircase.

With the individual goings and rises drawn out accurately, we can add in the treads and risers and see how they are routed and fixed into the stringer. The wall stringer that we can see in this illustration is a glulam timber that provides stability to the stair flight, as well as a physical recess for the treads and risers to fit into. The treads and risers are then wedged into place in combination with glue to create the flight itself. The wall stringer sits against the wall and is mechanically fastened to it. The stringer on the room side of the flight forms the basis for the additional decorative stair components that we will look at in the second fix section. The tread housing is routed 22mm down from the layout marks, and the risers are allowed 9mm backwards from the riser layout marks. A rounded nosing is extended a minimum of 16mm past the front of the riser on each tread. Specialist jigs can be purchased that are set up for common riser and tread intersection layouts. An additional amount of material is housed out after the thickness of the treads and risers to allow for the installation of the wedges, as can be seen in the illustration. The other illustration shows a through section of the installed treads, risers, and wedges - demonstrating how they all fit together within the housed stringer. An underside shot can also be seen, showing how the wedges look when installed from underneath the staircase.

The top tread is not the full depth of the other treads, instead being around 75mm overall, with a 50mm bearing on the structural beam that forms the stair opening. The flooring, also 22mm, is then able to meet the top tread with a flush surface being created. If we reintroduce the stair pitch line and make a perpendicular mark about 50mm off of the tread nosing, we can establish a line where the top of the stringer is likely to sit. There is no exact measurement requirement in play here, though 50mm is typical.

Again, there are no hard and fast rules about the depth of the stringer, as this is open to specific structural calculations, as well as design choices, though it should be suitably deep for the effective installation of the wedges, as we’ll see shortly. In this scenario, the top and bottom of the stringer are cut down and shaped to match the height of the skirting that will be installed later. The bottom of the stringer is cut down so that the upstand that is left is 100mm, the same height as the skirting will be. The top of the stringer is also cut to a height of 100mm off of the finished floor/top of the top tread, but it also cut with 100mm of extra length past the point where the stringer meets the structural opening beam. This notch out is not strictly load bearing/structural, as the stringer itself will be fixed to the wall using suitable anchors during installation, though the notch itself can help with locating the stringer in place during assembly.

With the stringer cut to shape, we can now turn our attention to the wedges and corresponding slots that are routed into the stringer in order to hold the treads and risers in place. This can be seen in the illustration, with 10-18mm wedges being driven into place behind the risers and under the treads, in combination with glue, to securely fasten these components in place. The risers are deep enough to meet the underside of each tread, allowing for a fixing to be driven through the bottom of the risers and into the back of the tread, aiding in stability as well as securing the bottom of the riser from being kicked in.

Glue blocks are also installed at the internal intersection of the treads and risers. These blocks are cut at 45 degrees and are approximately 100mmx50mm. They are secured in place with glue and small pins and provide additional stability to the joint where the risers meet the tread.

With all of these components in place, we can zoom out to see the bigger picture. The full straight flight of stairs consists of a stringer on each side of the treads and risers, attached to the wall on one side, and supported at the top by the structural opening beam. As is, this type of staircase would be best suited to installation between two walls, with the stringer each side being attached to and supported by these walls. This mitigates the requirement for built in newel posts and handrails.

If we instead look at how this staircase is positioned against 1 wall, we can see that a suitable handrail is missing from the outside stringer of the staircase, as well as from the landing area at the top of the stair. The installation of a handrail above the outer stringer requires a fixing point provided by a newel post at the top and bottom of the stringer. Depending on the length of the handrail required, or the exact shape and style of the stairs, multiple newel posts may be required in different locations to suitably support the handrail. A newel post is a solid timber component, typically around 3-4” in diameter. The posts are notched and mortised at numerous points along their length in order to sit correctly in their desired locations, as well as tying some of the other stair components together.

The primary consideration at this stage is how the stringer and handrail rail are attached to the newel post. Typically, both the stringer and handrail are fixed to the newel post in their respective positions through the use of a drawbored mortise and tenon, as well as the addition of glue to the joint. Section images of these joints can be seen illustrated here. The mortise and tenon for the handrail are typically centred in the width of the newel post and handrail timbers. Sometimes, the mortise and tenon that provide the connection between the newel post and the stringer are offset slightly in the width of the newel post, in order to avoid the routed dados on the inside face of the stringer from breaching the side wall of the mortise. The stringer still sits centrally with the newel post, and this variety of joint is known as a barefaced mortise and tenon, as it lacks a shoulder on one face.

Seeing as both the stringer and handrail are mechanically fastened to the newel posts involving a mortise and tenon, in this instance all of the components must be assembled at the same time. If the stringer is securely fastened to both of the newel posts first, we’ll never be able to get the handrail into place. As such, all of the relevant surfaces should be glued, with all of the components being slotted together first, and then the drawbore dowels being installed.

Before this task takes place though, the newel posts are likely to be cut and routed so that they sit appropriately in their desired positions. As can be seen in the illustrations, the bottom of the newel posts is routed out in a similar fashion to the stringers, so that the ends of the treads and risers can receive into them. These notches are typically made at the factory with the rest of the components, if the stairs are ordered from a specialist manufacturer. If the newel posts are bought separately, then these notches need to be marked out and cut on site.

The top newel post might also have a notch cut into that fits over the structural opening beam. There is no hard and fast rule in play here for how exactly this intersection occurs, as different staircase designs and overall scenarios are going to impact how these components sit together. That being said, it's good practice for at least some of the post to be notched over the beam, allowing for a more secure fixing and overall stability in the post. In the illustration, the top of the staircase sits in so that the back of the top riser is 10mm away from the outside face of the structural beam. This overcomes any deviation in the surface of the beam and allows for a small amount of squaring up to occur. In this instance, the newel post is notched tightly around this beam, with the depth of the notch reaching as far as 10mm behind the back of the riser.

With the staircase assembled with all of the relevant notches made, it can be lifted into place over the structural beam. The primary check to be made at this stage is to ensure that the treads are level when the staircase is sat in place. A spirit level can be used to check any of the treads, as they should all be level. A minor tolerance of a few mm is allowable under dire circumstances, though in reality there is no reason that the staircase shouldn't be installed perfectly level. If the treads are not level on a straight flight like this, the top of the flight can be lifted upwards until the treads are level. The distance between the bottom of the nosing and the top of the beam can then be measured. This is the amount by which the staircase needs to move downwards in order for the treads to be level and the staircase to be situated correctly. This can be caused by both an accumulated error in the layout of the stairs, or a discrepancy in the level of the ground floor finished floor. This distance can be cut off of the bottom step/riser/and stringer to allow for the staircase to move down, providing that the distance is not too much. An allowance of up to 10mm is acceptable here, though not ideal. Anymore and there are larger issues at hand.

The wall stringer is screwed into the wall, and the newel post can be mechanically fastened into the structural beam. A mechanical anchor may also be required at the bottom of the flight of stairs to retain the bottom newel post.

With the flight installed and securely fastened in place, it can be covered down suitably to protect it from the plastering stage. As previously mentioned, the other mouldings, spindles, and half newels can be installed after the plaster has been applied. This prevents these components from the potential of being damaged right up until the second fix stage when the other finished components are installed. We will take a look at how these components are installed in the second fix section.

Quarter turn stairs

Depending on the room that is available for the installation of the stairs, alternative shapes of a staircase may have to be employed. Whilst the rise of the total staircase will remain unchanged within a property, the exact variety and layout of the staircase will alter the total going and footprint that it takes up. Also depending on the shape of the staircase, the functional travel lines can change, altering the way that fluid movement is carried out during use. The first variation that we’ll look at here is the quarter turn staircase. This staircase changes direction by 90 degrees at some point during its rise. At one of the even increments of rise, a large “quarter landing” is installed, providing the basis for the change in direction, and allowing suitable space for fluid travel to take place. The quarter landing may be installed at any point during the rise of the stairs and will accommodate the requirements of the staircase. Typically, they are installed towards the top or bottom of the staircase, with about 2 steps before or after them respectively. When installed at the bottom of the staircase, there is no requirement for the bottom 2 steps to include a newel post and handrail, though they can be installed if desired.

When installed as a closed stringer style, as can be seen in the illustration, the quarter landing is contained within a routed stringer like the rest of the treads and risers. It's common for the upper flight, quarter landing itself, and lower two steps be delivered as individual pieces, allowing them each to be installed sequentially, slotting together as they go. When installing a staircase like this, the upper flight is installed first, with the rest of the components being installed as we work our way down. Importance is placed on ensuring that each separate section is installed correctly and meeting the criteria of plumb and level, so that any discrepancies can be minimised by the time we reach the bottom. Assembling the pieces together can be tricky, with a slow and methodical approach being best. It's hard to give an exact rundown of how these components are installed, as different manufactures will ship them differently, and the exact measurements will differ between staircases. For the most part though, all of the cutting and routing is done at the workshop, and so the only cutting likely will be the notch for the newel post at the top, and possibly a slight adjustment to the depth of the bottom step. The newel post at the corner of the quarter landing will likely reach down to the floor, and this will support the upper flight at the right height during installation. With the upper flight supported at the right height, the stringer can be fastened to the wall. The quarter landing can then be slotted into the appropriate housing slot and wedged into place. The bottom flight can then be installed appropriately. Again, the specifics may differ between staircases, though with all of the routing and cutting already performed, the assembly is relatively straightforward.

If the quarter turn staircase is of the cut stringer variety, then the quarter landing itself can be framed with dwarf stud walls and small joists, topped with flooring, installed at the correct height relative to the increments of rise and in the desired location. This is installed first, with the upper and lower flights being installed like regular cut stringer, supported from the floor to the quarter landing, and then up to the upper floor. In many respects, this is both easier to install and layout than the relatively intricate housings required for the quarter landing of a closed stringer.

Half turn stairs

Much like the quarter turn stairs, the half turn stairs feature a wider “half landing”, with a full 180 degree change in direction of the stairs. Whilst the total footprint of this style of staircase is no different in terms of occupied area to the straight flight staircase, the distance in length required for the installation is effectively halved. Once again, the closed stringer variety is supplied with routed stringer to support the half landing. With that being said, due to the shape of the staircase, it's not uncommon for the half landing to be framed conventionally, with two small straight flight closed stringer staircases being installed. This eliminates a lot of the intricate parts involved with creating the whole flight in a closed stringer variety.

This style of staircase offers a large half landing that can be beneficial in terms of a resting spot halfway down, for the less able-bodied that might struggle to climb the stairs in one go. It also offers the opportunity for the large space underneath the half landing to be framed out and turned into a full under stair cupboard, effectively utilising the otherwise awkward space.

Winder boxes and kite winding stairs

As we’ve just seen, the quarter and half turn staircase can alter the footprint of the staircase and offer more flexibility in terms of the installation of a function staircase. Taking that concept further, we can introduce a winder box, and kite winding steps within the staircase to minimise the footprint of the staircase. When looking at both the quarter and half turn staircases, both landings respectively only rise by 1 increment across their entire surface area. When looking at kite winding stairs, we can achieve multiple increments of rise within the same area that the landings take up, effectively reducing the number of steps that must come after the winder box. With the regulations about kite winding stairs in consideration, and the exact measurements and requirements of the stairs, a half turn kite winding staircase could see as many as 12 full steps implemented within the same area that a single rise half landing would occupy. Whilst it is more common for about 3-4 steps to be implemented within a winder box, it's still easy to see that this style of staircase can help to reduce the overall going of the stairs.

So, what are kite winding stairs? Instead of the conventional quarter or half landing, multiple even “kite winding” stairs are installed symmetrically around the geometric centre of the winder box. The steps themselves are so called due to their kite shape. As we can see in the illustrations of a regular quarter landing, the geometric centre is the point at which the two outside edges of the inner stringers meet. This is the point where the first and last steps before and after the landing begin and end.

For a 2 step winder, as can be seen in the drawing, there are no requirements for the going of the winding stairs, only that the minimum width of the tread towards the newel post must be at least 50mm from the front of the nosing to the riser, and so the winder box itself is simply split in half diagonally, with the two steps formed as such. The steps are routed into the outside stringer and inside faces of the newel post respectively.  

For a 3-step winder - the most commonly seen in UK residential properties - the steps are divided into 3 equal 30 degree segments, with the 2 angled risers coming out of the centre of each face of the newel post. When these 2 lines are extended past the newel post, the point at which the cross is the new geometric centre for the winder box - this is where the first and last regular step before and after the winder box begin and end.  

When we begin to add in more steps than this within the winder box, the process becomes more involved. With each added step, the effective size of the step within the winder box is reduced, and so we must be conscious of the regulations governing the size of the kite winding stairs. Regulations state that the going of the winding stairs must be no less than the going of the regular steps, though they can be more than the going of the regular steps. The measurement of the going for the winding steps is taken through an arc of the centre of the staircase. This can be seen in these illustrations. To draw this initial arc that connects the two centre points of the straight flights of stairs, we must perform a simple calculation. First, we must decide upon the number of steps within the winder box. In this example, we’ll perform the calculation for 5 steps within the winder box. If there are 5 equal divisions within this quarter turn, then there would be 20 divisions within the whole circle when extrapolated. If the central going of each winding step is 250mm (in this example), then the total going of the quarter arc is 1250mm, with the circumference of this circle being 5000mm. We can simplify this step by saying 250x20 =5000mm. To find the centre point of this circle, and the geometric centre of the arc/winder box, we must find the radius of this circle. To do that, we can simply divide the total circumference by 2pi.  

Going x number of steps in a full circle / 2 pi - 6.2832

Resulting value - half width of the staircase = offset from corner of the newel post

250x20 = 5000c

5000/2pi = 796 - radius of the arc/circle

 This looks like so when written out. As we can see, the radius of this circle/arc is 796mm. We can measure backwards and then up from the middle of the winder box where the two centre lines intersect, to find the geometric centre of the winder box. An arc struck from this point between the two centres of the straight flights will form a consistent going arc. It is worth noting here that the actual going of the winder steps is measured centrally between the two extreme-going arcs. This is typically an arc swung around the newel post, and another between the two outside edges of the stringers. This means that the actual effective going centre of the treads is wider than this initially drawn arc, though there is no good way to calculate and draw this, other than through trial and error. That being said, when bearing in mind that the going of the winders must be no less than the going of the regular treads, whilst imperfect, the winder step going will always be more than the regular going of the steps.

Once the geometric centre of the winder box is found, the appropriate divisions can be extrapolated at equal increments. For a 4-step winder box, the steps fall at 22.5-degree increments, and 18-degree increments for a 5-step winder box. This centre once again defines the point at which the first and last steps before and after winder box begin and end. The going is measured through the centre arc of the winding steps for staircase that are less than 1m wide. For those that are wider, the going is measured at 2 points, 270mm in from each inside and outside going boundary. The going values for both must fall within the allowable pitch of 42 degrees and must be not less than the going of the regular treads. 

There are a whole other set of regulations that dictate the installation of commercial and industrial stairs, though here is not the place to cover them.  

Under stair cupboards - this is a combination of studwork and sheathing that we’ve already looked at, to a lesser degree, in order to form a more finished and functional aesthetic under the stairs. If youre gonna have a cupboard nder there, it doesnt really matter if the underside of the stairs is covered, but still an option. If the stairs are going to be open, then unless theyre made decoratively in the first place, then we probably want to cover it. If the plan is to store things under the stairs either way, its probably tidier to box it in. This will close the hallway space off more, making it feel smaller, but it allows all the necessary unsightly things to be put out of sight. A cupboard like this is great for putting laundry baskets, bags of dog food, hoovers/mops/brooms etc. These are all necessary household items, but do we really want to look at them all the time. Out of sight out of mind. 

The bottom is way too tight for any practical use - there are a load of reasons why youd want to frame it out. There are loads of bespoke cupboard manufacturers that could fit fitted cupboards under these stairs - in which case, just leave it as is. If notm we can form the cupboard with studwork .