15th November 2016 at 11:52 am #596TimKeymaster
What are the main features of Stair Nosing (Stair Edging)?
There are five main features of Stair Nosing:
III Slip Resistance of Tread material
IV Tread Surface
V Tactile Surfaces
A Stair Nosing should have dimensions of between 50mm and 65mm across the upper tread surface and 30-55mm on the riser. (Earlier these dimensions were stipulated only as being 55mm x 55mm respectively). They are intended to ensure that a good step definition can be achieved. This applies when a suitable colour contrasting with the floor covering material (see next topic) is selected.
The summary above is a compilation of the guidance – sometimes a little confusing – contained within the following documents:
Building Regulation 2010 (Approved Document K 2013 edition)
Section K1.7(a) “For buildings other than dwellings – ‘use a material that will contrast visually, a minimum of 55mm wide, on both the tread and the riser.‘”
Section K1.10(a) “For common access areas in buildings that contain flats – use a material … 50mm to 65mm wide on the tread and 30mm to 55mm on the riser”
Building Regulation 2010 (Approved Document M1/M2 2013 edition)
Section 1:33 ‘All nosings are made apparent by means of a permanently contrasting material 55mm wide on both the tread and the riser.
BS8300:2009+A1:2010 – Section 5.9.5 p26
‘The material should be 50mm to 65mm wide on the tread and 30 to 55mm on the riser’
BS9266:2013 – Sections 6.8 p8 and 8.2 p16
”The material should be 50 mm to 65 mm wide on the tread and 30 mm to 55 mm on the riser, and should contrast visually with the remainder of the tread and riser.”
In the early days of the DDA the guidance was quite restrictive. The dimensions required were declared as being specifically 55mm on both the tread and the riser. This resulted in some rather cumbersome Stair Nosing designs that have never been popular with specifiers. More recently and with the advent of the Equality Act the guidance has allowed specifiers a little more latitude. The 50 to 65mm and 30 to 55mm brackets for Stair Nosing tread and riser dimensions respectively are preferable. They ensure that good design can also go hand in hand with satisfying the regulatory guidance for a safe stair.
This apparent difference in the regulatory guidelines can be reconciled since both sets of guidance are correct. As has been stated, the principle requirement is that the nose of a step is clearly defined. A proprietary Stair Nosing within any of these dimensions can achieve this. Step dimensions and the degree of foot traffic can also influence the choice of Stair Nosing to be installed.
The principle function of a Stair Nosing in this regard is to provide the right dimensions for the visual contrast needed to make a clear definition of a steps nose.
II: Colour: Light Reflectance Value (LRV)
The Light Reflectance Value (LRV) of a colour is a measure* of the amount of visible and usable light that reflects from (or absorbs into) a given coloured (painted) surface. Simply put, LRV measures the percentage of light a (paint) colour reflects. LRV is measured on a scale that ranges from 0 (absolute black, absorbing all light) to 100 percent (pure white, reflecting all light).
*Total quantity of visible light reflected by a surface at all wavelengths and directions when illuminated by a light source – BS 8300:2009
In the context of the creation of a ‘safe stair’ this is perhaps the main Stair Nosing feature. This is because it is the colour difference between the Stair Nosing and the stair floorcovering that creates (BS 9266:2013):
‘a permanently contrasting continuous material for the full width of the stair on both the tread and the riser, to help people with a visual impairment appreciate the extent of the stair and identify individual treads.’
In the early days in the establishment of the DDA, the Joint Mobility Unit (JMU), a division within the RNIB, worked in conjunction with Reading University on Project Rainbow. This was set up to establish a system of colour measurement. The aim of project Rainbow was to give a value to any given colour. The outcome was the grading of colours by the degree of light reflectance from a given surface. A scale was established where black was 0 and white 100. Different colours from different surfaces were then graded between these two parameters.
The JMU then undertook their own empirical trials and concluded that a colour (Light Reflectance Value – LRV) difference of 30 points gave a definable contrast that could be differentiated by the visually impaired. Taking this a stage further, and applying it to the difference of LRV between the Stair Nosings and the surrounding floor covering on a staircase, a ‘ladder effect’ is created which is key to the establishment of a contrast on the steps that makes a staircase safe.
References to the guidelines for LRVs can be found in the following documents:
- Building Regulation 2010 (Approved Document K 2013 edition) – p6 section 1.10 and p51 Appendix A
- Building Regulation 2010 (Approved Document M 2013 amended) – Introduction. pp15 &16
- BS8300:2009+A1:2010 – Annex B1 p183
- BS9266:2013 – Section 8.5 p16
Couple this requirement for a colour difference between a Stair Nosing and the floor covering on a stairway with the Stair Nosing dimensions in Feature 1 and the essential requirements for a Stair Nosing that will satisfy regulatory guidelines are established.
‘The Ladder Effect’ is created by the contrasting band of colour provided by the Stair Nosings if the LRV difference with the floorcovering is 30 points. When viewed from the top or bottom of the stairs the impression should be of clearly identified stepping positions as if they were the rungs of a ladder. This is of particular benefit to the partially sighted. This, along with correctly dimensioned steps and well positioned handrails, contribute to making a staircase safe for all users.
III: Slip-Resistance of Tread Material
The upper surface of a Stair Nosing is designated the tread, as is the horizontal section of each step. On a Stair Nosing the tread needs to offer a slip-resistant surface. This will help prevent the incidence of mishaps when footfall is ascending or descending a stair.
The guidance for the slip-resistance of Stair Nosing tread material is linked to that of the floorcovering on the staircase. The following Documents make reference to the slip-resistance of Stair Nosing tread material. They also give guidelines for their performance in this regard:
- Building Regulation (Document M) – reference refers to BS8300 (see below)
- BS5395.1:2010 – Section 10.6 p14
- BS8300:2009+A1:2010 – Section 9.5 p26 and Annex E.5 p196
- BRE IP15/03 – (13)
In both cases the guidance for the slip-resistance of the Stair Nosing tread is that the material used should have a ‘Rubber Boot – 95’ Pendulum Test Value (PTV) of at least 36 in both dry and wet conditions. The Pendulum test method is a standard system for the measurement of the resistance of floor covering materials. The practical problem however is that once a Stair Nosing is installed, due to the restricted width of a step’s tread, there is insufficient room for the pendulum to be swung on site. Therefore, the guideline measurement can only be achieved in factory conditions prior to any installation. This means that the measurement of used tread material on site is not possible.
(A PTV measurement of the tread material on the top most step of a stair case can be undertaken, and this may give an indication of the tread material on the other Stair Nosings on the flight, but it is no more than that – an indication).
For a used or on-site measurement of Stair Nosing tread slip-resistance an additional means of measurement is with a surface roughness micrometre. The Health and Safety Executive (HSE) has established guidelines in its Slips Assessment Tool (SAT) which is a freely downloadable computer software package that allows an operator to assess the slip potential of pedestrian (walkway) surfaces. It indicates that if a material has a micro roughness reading greater than 20 µm, then it can be classified as being of ‘Low Slip Risk’.
Slip Potential Rz Value1 PT Value1
High Slip Potential below 10 µm 0 – 24
Moderate Slip Potential 10 – 20 Mm 25 – 35
Low Slip Potential 20+ Mm 36+ (minimum requirement)
1 RZV=Surface Roughness Values and PTV=Pendulum Text Values
As a consequence of the limitations inherent in the opportunity to achieve reliable on-site slip-resistance measurements of Stair Nosing tread material, the current ‘best practice’ guidance is a combination of the two methods. It is recommended that specifiers, contractors and end users look to install Stair Nosings with tread material that has been independently laboratory tested to have a PTV greater than 36 and similarly a micro roughness reading of more than 20 µm – both in wet and dry conditions. It is then possible (if necessary) to use a micro roughness metre on site. This can re- measure the µ value and comparisons can be made to give an indication of any changes over time. Due to the variability of site conditions it should be stressed that this is very much only an indication.
The following extract from BS8300:2009+A1:2010 – Annex E.5 p196 sums up the position:
“Where slip resistance is required for nosings and treads, the slip resistance needs to be equivalent to that expected for level surfaces. A PTV greater than 36 is considered to be suitable, as pushing and turning are unlikely on stairs. On existing nosings, the slip resistance of step nosings are generally expressed by their Rz roughness value as PTV is difficult to measure. In such cases a roughness Rz value of 20μm is recommended.”
IV: Tread Surface
Traditionally the Stair Nosing tread material is contained within a shallow channel on the upper surface of the Stair Nosing carrier. The carrier is usually made from aluminium or PVCu. In relatively rare instances it can be made from cast iron, steel, brass or bronze.
More recently (October 2003 – That is Mike Roys’ paper “IP5”) however, work undertaken at the Building Research Establishment has concluded that the tread material should extend right across the upper surface of the Stair Nosing.
This recommendation is contained within BRE IP 15/03 which covers many aspects of stair design with respect to safety. It indicates that, particularly in descent, a person’s foot fall will usually impact at an angle on the very front of the nose (edge) of a step. The shorter the going of the tread the more likely this is to occur.
As a consequence, the improving guidance that comes from the work undertaken at BRE identifies that the most practical and safest format for a Stair Nosing tread material is for it to cover the whole of the upper surface of the Stair Nosing carrier – right up to and over the front edge.
This ensures that footfall, particularly in descent, is onto a slip resistant surface. The importance of this is heightened when the tread going is at the shorter end of the recommended design and construction dimensions.
The relevant statement in BRE IP15/03 (p6) is:
“Slip-resistant nosing: The risk of slipping can be reduced if the proprietary nosing incorporates a material that has slip resistant properties at the point where contact is likely to be made………….. the slip resistant material must continue to the very (front) edge of the tread.”
V: Tactile Surfaces
In addition to the guidelines for the steps on staircases and their respective Stair Nosings there are also recommendations for the surfaces on the approaches to stairways – namely there should be a corduroy tactile surface at the top and bottom of flights of stairs. The purpose of these surfaces is to provide the partially sighted with a specific warning of the presence of a change in level by means of steps.
These recommendations cover the installation of a tactile surface with certain prescribed dimensions at the approaches to a stairway. The guidelines can be found in:
Building Regulation Document M – Section 1.33 c and d p21 & p22
BS8300:2009+A1:2010 – Section 3.10, Section 5.9.6 p27 and Fig 9 p28
BS9266:2013 – Section 6.8.2 p9 and Fig 2 p10
In the case of the stairway approaches the requirement is for a corduroy tactile surface. This is opposed to the blister variety found for example at crossing points on pavements and the edge of railway station platforms.
As can be seen the recommendations for the dimensions and positioning of these surfaces are quite specific, and note should be made that they are not placed on half landings* – only at the top and bottom of a flight.
As experience through use and application has been gained, although the BR and BS guidelines are for stairways in general, the practical installation of these corduroy tactile surfaces has been mainly for external applications. A choice to include an internal installation should be determined by taking into account the safety considerations of the site. The principle decision making process being to ensure a stairway is safe for the volume and type of foot traffic expected.
*The exception being when there is an entrance/exit to/from the half landing.
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