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Stair design is a critical part of ensuring that it can perform safely, meet building regulations and high standards.
The BWF Stair Scheme aims to help designers and specifiers achieve the design they wish to achieve without sacrificing performance.
We also support our manufacturers, who often play a significant role in design, to help them produce stairs that meet the expectations of clients in terms of a stair’s look, while ensuring they manufacture the highest quality stairs.
We have produced the BWF Stair Design Guide – for architects and specifiers to use to help make their stair to the highest of standards.
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Protecting the students of Liverpool: HOPE STREET STUDENT ACCOMMODATION
JELD-WEN, the leading manufacturer of timber windows, doors and stairs was chosen to supply fire protected timber stairs for a pioneering student accommodation development in Liverpool.
The Hope Street site was a former 1867 hospital which was previously demolished and has now seen one of the biggest development projects delivered in Liverpool’s historic Georgian Quarter.
The site (left) consists of a 339 bedroom, mixed use development of 10,000 sqm. It includes apartments and accessible studios complete with fully fitted kitchens and ensuite bathrooms, all within a purpose built student centre including a gym, bars and restaurants.
The build itself was of particular significance with a volumetric construction system being used, which is not usually available in the UK. Each building was constructed with highly insulated, FSC/PEFC certificated timber frame modules which were manufactured and delivered on site fully fitted, decorated to a high standard and ready wired and plumbed for all services. The stairwells were created by the walls of each module converging to create a rectangular shaft through the building where the stairs could later be installed
The importance of this choice of construction method being that it reduces the build time by 30% compared to traditional methods, which allowed the accommodation to be ready in time for the September 2015 intake of students.
Timber stairs were specified for all residential levels, but it was crucial that these were fire protected communal stairs due to the multi-occupancy nature of the building. JELD-WEN is the first and only volume UK timber stairs manufacturer to be certified by the BRE Loss Prevention Certification Board (LPCB) for fire-protected timber stairs through the BWF Stair Scheme. The LPCB tests and verifies designs, performance, manufacturing process and quality assurance throughout manufacture to establish whether the timber stairs are serviceable and an effective means of escape, even after an extremely hazardous fire.
In addition, JELD-WEN also faced the challenge that the stairs supplied were for a seven storey building which is higher than normally specified for timber stairs.
Roy Anderson, Technical Manager at JELD-WEN stairs said: “Despite the challenging nature of this project, The Hope Street development was a fantastic project to be a part of. Our team at JELD-WEN stairs worked closely with building control to ensure that the stairs we supplied would meet the Building Regulations with flying colours.”
Hannah Mansell, manager of the BWF Stair Scheme, says:
“The specification of BWF Stair Scheme accredited stairs was a wise move in this challenging and innovative build. The scheme promotes effective design and reliable manufacture, developing guidance where standards and regulations are in conflict, and ensuring best practice advice is passed to installers to reassure that such products consistently meet the relevant performance requirements for loading, deflection and fire resistance where needed.
“The standard expected of BWF Stair Scheme members for their stairs is extremely high to ensure quality and safety. There is no straightforward method for Building Control to verify that a stair has been manufactured correctly and complies with the relevant standards and Building Regulations, other than looking for the Stair Scheme badge.
“The increasing use of timber stairs in multi-storey, multi-occupancy buildings such as this student accommodation project brings this into sharp focus. If a stair failed during an emergency evacuation, the consequences would be devastating. The common flight stair may act as one of the routes of escape in the event of fire. So it is vital that it is able to resist the effects of the fire and maintain its integrity. This demands a higher level of accreditation, which JELD-WEN has achieved through rigorous product development and testing.”
Fire Protected Stairs
In medium-rise buildings, the common flight stair may act as one of the routes of escape in the event of fire yielding serious implications of this for the safety of the occupants of the building and the emergency rescue services.
BWF Stair Scheme Member, JELD-WEN, was been awarded Best Internal/Interior Product for its fire-protected stairs at the Housebuilder Product Awards 2013.The inaugural Awards, which showcase and reward excellence and innovation amongst suppliers to the UK housebuilding industry, were presented at a special event at Edgbaston Stadium in Birmingham on Thursday 20 June, by columnist, author and former England Cricketer Ed Smith.
JELD-WEN is the first and only UK timber stairs manufacturer to be certified by the Loss Prevention Certification Board (LPCB) for fire-protected timber stairs through the BWF Stair Scheme.
JELD-WEN developed its LPCB Certified fire-protected stair range by working with the British Woodworking Federation (BWF) and the BRE and undertook an extensive test programme. As a supplier of these products, JELD-WEN is authorised to label its stairs with the instantly recognisable LPCB ‘horseshoe’ mark alongside the new BWF “badge”.
These certifications not only demonstrate that the stair is not consumed in a fire, but also that JELD-WEN’s fire-protected stairs maintain their normal function after a fire event within the stair enclosure. One test requirement, following the actual fire test, is that the stair will still carry a large static load, confirming its functionality as an escape stair.
Tony Baker at the BRE/LPCB said: “This certification is about giving specifiers and developers more confidence about products that meet fire protection requirements. They should be in no doubt now that JELD-WEN’s timber stairs can be specified for low and medium rise blocks, and that they help minimise fire risks in the buildings they are designing, specifying or managing.”
Phil Chimento, JELD-WEN General Manager – Stairs, said: “The Award is fantastic recognition of our efforts to ensure that our stairs meet and exceed regulatory standards. We’re always looking at how we can improve our product range to provide a better service for our customers and this Award is a firm step in the right direction.”
The features of safe stair design
Stair Safety: BWF Technical Director Kevin Underwood summarises the features of good stair design
A timber staircase is an opportunity to show off design flair and innovation, but the desire to create a centre-piece for the home should not surmount consideration given to the safety of the stair. Stairs present a risk of injury through slips, trips and falls and while a home owner may believe that this type of accident would not happen to them the statistics belie this view. In their report Can the home ever be safe? the Royal Society for the Prevention of Accidents (RoSPA) states that every year there are over 300,000 visits to Accident and Emergency following falls on the stairs.
Most serious falls occur in descent a person falls backwards and slips down the stairs, injuring themselves on the nosings of the steps (they pass) or when they hit the floor or other objects at the bottom of the flight. Occasionally, more serious injuries occur when the user falls forward rather than backwards. In ascent, the injuries tend to be less severe as the fall is most usually forward onto the steps above; but again, should the user fall the other way (backwards rather than forwards) much more serious injuries can occur. Carpets can reduce the severity of an injury while hard, sharp edges are likely to cause more serious injuries.
Accidents can be reduced by attending to those characteristics of a staircase that affect a user’s ability to use the stair safely. The geometry of the stair, the rise, the going and the position and shape of the treads can affect the ability of the user to safely place their feet and avoid tripping or slipping on the stair. But if a user does begin to fall, a suitable handrail can allow them to steady themselves and at all times adequate guarding can prevent users falling to the side of the stairs.
Under-step and over-step
Many accidents are caused by an under-step or over-step in both ascent and descent. In ascent, an under-step is where the foot is not placed fully on the next step up and an over-step is when the toes catch the riser of the next step up or catch under the nosing. In descent, an over-step is where the foot lands beyond the tread of the stair and an under-step is where the heel catches the nosing or riser of the step above.
Consistent rise and going
A key cause of under-stepping or over-stepping is when there is inconsistency in the rise and going of a stair. When a person starts to ascend or descend a stair they subconsciously determine the appropriate movements they need to make with their legs and feet based on the first one or two steps they take. This process, known as ‘proprioceptive feedback’, makes the user vulnerable to variations in the rise and going of a stair as they expect to step up or down by the same amount throughout the flight. Variations between steps are unexpected and can lead to the user tripping or slipping. It is, therefore, important to allow only small variations between steps of around 1% of the design dimensions.
When a user places their foot on a step the best support is provided when they can place most, if not all, of their foot on the tread. But when the going falls below 250mm this is not always possible and in order to get adequate support, users begin to turn their feet to the side at each step. 95% of domestic stairs fall into this range, and walking with turned feet has become the expected method of walking on a stair. However, the risk of slipping on nosings is increased when the amount of the foot that overhangs the tread increases; so the user that doesn’t turn their feet is in danger of slipping.
Where stairs are designed to have an open rise the treads should overlap and there should never be horizontal gaps between treads when the stair is viewed on plan. In order to protect children who may use the stair the vertical gaps between treads should be small enough to prevent a 100mm diameter sphere from passing through.
Fewer than expected accidents occur on stairs with winders (stairs change direction without a landing), even though winders are often used in narrow, steeper stairs when space is at a premium. It is possible that users take less care when walking on straight flights and are more cautious on winder flights. Well-designed winders providing an adequate going on the walking line and at least 50mm of tread at the newel can be safe to use. However, winders that cannot provide adequate support at each step can lead to users dropping over 600mm after a slight slip near the newel.
Users of stairs quite often don’t use the handrails provided and may feel they are unnecessary. Where there is adequate going for the user to place their foot comfortably and the rise is not too high, users tend to feel confident and do not use the handrail to steady themselves or to pull themselves up the stair. However, handrails are an essential safety item. When a loss of balance occurs users are able to catch hold of a suitable handrail and stabilise themselves within a fraction of a second. It is, therefore, essential that the handrail is positioned so that the hand can reach it quickly and, as a fall can occur on any part of the stair, the handrail needs to be within easy reach throughout the whole flight.
To adequately protect users from falling from the side of the stair any fall of more than 600m should be protected by guarding. This should be strong enough not to give way when weight is applied to it and it should be tall enough to stop people falling over the top of it in normal use. To protect children who may use the stairs, any gaps in the guarding should be small enough to prevent a 100mm diameter sphere from passing through.
The surface finish or covering to a tread can affect the likelihood of slipping and worn coverings can cause a trip. Where the going of the stair is 300mm users tend not to be affected too much by the slipperiness of the surface but on stairs with treads less than 300mm consideration should be given to a measure of slip resistance at the nosing. This is where first contact is made in descent and a slip resistant surface can help turn a potential slip into a slight loss of balance which can be corrected by gripping the handrail.
The characteristics described above are just representative of the issues affecting the safe use of stairs. There is a wealth of research into how people use and perceive stairs and into what makes stairs both safe and unsafe to use. So while the statistics show that there are a lot of injuries attributed to trips, slips and falls on stairs in the home, stairs should not be considered as inherently unsafe, as the risks associated with stairs can be mitigated through good design.
Article by Kevin Underwood, Technical Manager of the British Woodworking Federation
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1. What are the key parts of a staircase?
The humble staircase can open up a wealth of terminology that can cause confusion. The diagram below helps to demystify some of these terms:
Strings: A span of timber to which treads and risers are attached to support a flight or run of stairs
Tread: The horizontal part of the stair that is stepped on.
Risers: The vertical part of the stair (where no risers are present this would be referred to as “open risers”). The number of steps in a staircase is counted by the number of risers, not the number of treads
Balustrade: A row of balusters (spindles) topped by a handrail serving as a safety guarding and along the edge of a staircase
Handrail: Following the staircase to support and guide during ascending or descending a staircase and an element to grasp in case of a fall
Newel: A large baluster or post acting as a structural element to anchor the balustrade to the floor or stair.
Spandrel: The triangular space underneath a staircase (when there is not another flight underneath)
Winder: A stair that is narrower on one side to enable a turn in the staircase. A series of winders form a circular or spiral stairway. When three steps are used to turn a 90° corner, the middle step is called a kite winder as a kite-shaped quadrilateral
Apron: A facia covering the ends of rough strings, carriage pieces, and the joists of landings.
Other key terms
Flight: An uninterrupted series of steps.
Rise: The height of an individual step (i.e. this differes from the hight of a riser as it refers to the height that must be stepped)
Going: The depth of an individual step
Pitch: The slope of the staircase measured as the ratio between the rise and going
Walkline: The path that an individual would follow up or down a staircase
2. Is it possible to have two steps in a winder flight?
The problem with a two step winder is that the walk-line going can often exceed the limits set by the building regulations. Winders should have a rise that is the same as the other flights forming the staircase and a going that is not less than the going of the other flights.
The going of the winder should also fall within the limits set, for example, by table 1 of Approved Document K. Where the going of a private stair should be between 220mm and 300mm. To stop the going from becoming too long , causing the user to have an uncomfortable stride pattern, the control formula of twice the rise plus the going (2R + G) being between 550 mm and 750 mm should also be applied. If the stair is narrow then the walk line going may not exceed these limits and the stair would comply with the building regulations. However, wider stairs would cause the walk-line going to become too much making the stair non-compliant.
There are two standards which each provide a method to determine the walk-line going;
BS 585-1: 1989, Wood stairs — Part 1: Specification for stairs with closed risers for domestic use, including straight and winder flights and quarter or half landings and
BS 5395-1: 2010, Stairs – Part 1: Code of practice for the design of stairs with straight flights and winders.
3. What is the difference between a split newel and a two part newel?
A split Newel refers to a Newel Post that has been split in length and can form the end of a balustrade when it finishes against a wall. A two-part Newel is formed by a newel base which is often joined to the string and an upper part that is fixed into the newel base (care should be taken when using newels of this type to ensure that they can support sufficient load).
For a full list of standards and regulations for staircases download a copy of the BWF Stair Design Guide