Stair carpets

Testing can help to identify carpet products suitable for use on staircases in domestic and contract situations.

Carpet on stairs, in both domestic and contract installations, is subject to some of the most severe wear conditions of any carpet application. This is because the forces imposed by a person going up and down stairs are quite different from those imposed by the same person when walking on a flat surface. In addition, many people do not just walk up and down stairs, but run, or take them two at a time.

At the top and bottom of the stairs, there is inevitably a twisting or turning point. However, the most vulnerable part of the stair is generally the nosing, which receives severe physical abrasion in use.

All this means that great care is required when specifying carpets for stair installations.

Testing

There is no single test procedure which will predict the different properties of all carpet types in relation to use on stairs. However, there are a number of tests that can help to identify the most suitable product for either domestic or contract installations, including:

• pile density – this ensures that when carpet is flexed through ninety degrees over a 12.5 mm radius, no 'grinning' occurs, so that the backing is not visible through the pile
• stability – good dimensional stability properties will ensure that the product can withstand the forces to which it is subjected during use
• delamination properties – for secondary and foam backed products
• tuft bind – an important property where tuft loss on stairs is concerned. See table 1 for typical minimum force requirements.

The Lisson Tretrad machine is used to assess the suitability of carpet for stairs by identifying such parameters as:

• wear to backing – partial loss of tufts or loops
• burst loops/loss of yarn, ply twist or fibre crimp
• degree of cobwebbing/hairiness measured in fibre length
• tuft bind – typical minimum force requirements (BS 5229:1975)
• pattern changes at stair edge compared against area exposed to flat treatment under test.

Fitting carpets on stairs

There are a number of practical considerations to ensure the longevity of a carpet on stairs. It is important to ensure it is fitted correctly to achieve satisfactory performance. A good grade of underlay should be used to support the wear life of a carpet, making sure that it is butted tightly to the gripper, and securely fixed over the nosing.

A common problem can be tuft disturbance at the bottom of the riser just above the gripper especially if the underlay has not butted tightly. This can cause a gap behind the carpet and, with the interaction of the foot catching this area, tufts can be dislodged. Foam backed carpets can also cause problems if they are not fully stuck down, or fitted with a prefabricated nosing.

Because of the severity of wear on a stair length it is suggested that extra material is allowed for, to enable periodic moving to equalise wear. Where movement is not feasible, additional material should be retained for subsequent replacement. Both carpet tiles and fibre-bonded products should be installed with prefabricated nosings.

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