Geoff Wilkinson looks at issues and regulations relating to designing buildings to meet the needs of the visually impaired
World populations are becoming increasingly older, with average life expectancy increasing by 20 years since 1950 and predicted to extend by another 10 years by 2050. With increasing age, adults become more susceptible to eye disorders such as macular degeneration, cataract, glaucoma and diabetic retinopathy. In the UK, the number of blind and partially sighted people is expected to rise from 1.79 million in 2010 to 4 million by 2050.
For the visually impaired, colour contrast in interiors is important. On arrival inside a building, people look around to understand the area they have entered. People with good vision usually do this instantly. Visually impaired people, however, often need to pause to gather information about the space or to adjust to the change of luminance. They often first try to discern the visual contrast at the wall/ceiling junction, usually the least cluttered area of a room, to establish a change of surface area or feature. When they start to move around, they concentrate their vision downwards, within 2m, and scan the area in front of them for contrasts between features.
The main feature of a surface, which appears to be strongly correlated with the ability of visually impaired people to identify differences in colour, is the amount of light a surface reflects, or its light reflectance value (LRV). This is the total quantity of visible light reflected by a surface at all wavelengths and directions when illuminated by a light source. The LRV scale runs from 0, which is a notionally perfectly light-absorbing surface that could be assumed to be totally black, up to 100, a notionally perfectly reflective surface that could be considered to be the purest white. For all practical purposes, black is always greater than 0 and white never equals 100.
Part M of the Building Regulations stipulates a minimum difference in LRV between two adjoining surfaces of 30 points for new-build and major refurbishment projects and BS 8300:2009 says this is best practice for all buildings. While there is considerable confidence in recommending a difference in LRV of 30 points or more, there is also much anecdotal evidence to suggest that a difference of about 20 points may still be acceptable. Differences less than about 20 points may not give adequate contrast for visually impaired people.
It is thought that LRV differences are less important between two large areas, for example between a wall and a floor, than between a small object on a larger background surface: a lever handle on a door, for example.
In addition, there is very little research-based evidence concerning the influence of surface textures – differences in gloss levels of surfaces, for example – on the visual contrast required by visually impaired people. High-gloss finishes should, however, be avoided for large areas such as floors, walls, doors and ceilings.
Currently there is no design tool to help contractors, architects, designers and access consultants evaluate what exactly constitutes good colour contrast in their projects. Furthermore, contrast is virtually impossible to determine at plan assessment stage and relies instead on the often highly subjective view of the building inspector at completion. The BSI committee responsible for BS 8300 is undertaking further work in this area but, in the meantime, what can be done?
Wherever possible, the whole door and architrave should contrast visually with the surrounding surfaces and the leading edge of the door should contrast with the wall in which it is opened. The door, handles and finger plates should be sufficiently different in colour to the door – so chrome on chrome, for example, should be avoided.
Skirting boards should be in a contrasting colour to the floor covering, because a skirting board the same colour as the wall, but different to the floor, will give an accurate indication of the size of the floor. However, if it is in a colour similar to the floor, the focus will be on the top of the skirting and the wall, making the space appear wider than it actually is.
General obstacles and furniture
Projection of obstacles and furniture into the walking space should be minimised. Those that are essential should be contrasted against floor and wall surfaces and other backgrounds against which they may be viewed. A very common mistake is to specify the standard Part M pack in white when using a white, beige or light-grey colour scheme in a toilet. There is an option to use a dark blue pack instead, which helps to create contrast.
Geoff Wilkinson is managing director of Wilkinson Construction Consultants www.thebuildinginspector.org