You've got a floor to cover, but which material is going to serve your client best – and for the longest – for the least amount of money? Peter Mayer of the Building Performance Group shines the spotlight on the whole-life costs of PVC, linoleum and carpeting
Many floor covering options are now covered by European standards that include a classification based on intensity of use. This is a great benefit to specifiers and consumers, as it means that an informed choice can be made with regard to durability.
The three types of floor covering that are considered here – PVC, carpeting and linoleum – offer an idea of the whole-life costs and issues.
PVC and linoleum – homogenous products for which the same material tends to be used throughout – are described in terms of the thickness of the covering.
Types of PVC floor covering include foam-backed PVC to BS EN 651; semi-flexible PVC to BS EN 654; PVC on jute backing or polyester felt backing to BS EN 650; cushioned PVC to BS EN 653; and PVC with cork backing to BS EN 652. Linoleum options include linoleum on corkment or foam backing to BS EN 687 and BS EN 686, respectively.
<B><font size="+1">Factors affecting durability</font></b>
<B>Specifying for areas of use</b>
Floor coverings should be selected from the appropriate class for the intended location and use. Use classes for resilient coverings are set out in BS EN 685 for domestic, commercial and light industrial use.
In the commercial sector, four levels of use are defined: moderate, general, heavy and very heavy. Heavy commercial (class 33) would be used in areas associated with heavy traffic in corridors, department stores, schools and open-plan offices.
Textile floor coverings – carpets – have domestic and commercial use classes defined in BS EN 1307. In commercial situations, general contract (class 3) indicates a heavy-use intensity. For particularly tough use, heavy contract (class 4) carpets are suitable.
The service lives of floor coverings depend on the appropriate class being selected for the use. Longevity of the covering may be increased by overspecifying – for example, by installing a heavy commercial covering in an area with a moderate use.
<B>Properties of coverings</b>
The wear resistance of carpets is largely a function of the density of the piles. Other properties that influence the resistance to wear include the type of fibre or blend, pile thickness and fibre anchorage. The life expectancy of synthetic fibres can be twice that of natural fibres.
All things being equal, the thicker the linoleum and PVC wearing layer, the longer they last. Typically, linoleum and PVC floor coverings are between 1.8 mm and 3.2 mm in thickness, although the range of wearing layer thickness is much wider – between 0.7 mm and 3.2 mm for a homogenous sheet or tile. Furthermore, PVC coverings can be classified by wear group – T being the most wear-resistant, P, M and F representing decreasing wear resistance.
A suitable adhesive should be used. Where carpet tiles may need to be lifted, consider using a semi–permanent or tackifier adhesive, which will allow tiles to be lifted without damage. This is particularly cost-effective where raised access floors are installed.
Ensure that adhesives are compatible with both the substrate and the covering system.
Locate seams and joints in areas that do not have high wear. Areas at high risk include stairs, doorways, lift entrances and narrow corridors or circulation areas. If necessary, position the joints where a protective cover can be installed.
Removing grit that has been embedded in carpets is the key to long life. This may not be possible through vacuum cleaning alone. In areas of heavy traffic, worn sections of carpet may need replacement after a few years. Scrubbing or use of abrasive cleaners will decrease the life of linoleum and PVC.
<B>Preparation and condition of the subfloor</b>
Solid floors should be damp-proofed. Floor coverings, especially carpets, and many adhesives and smoothing compounds may be adversely affected by moisture. Concreted and screeded floors should be fully dry before covering. For carpets, a relative humidity reading of less than 75% in the BS 5325 dampness test is required before laying.
Suspended timber boarded floors need to be in good condition. Where timber floors are not level, the surface should be covered with an underlay, such as 4 mm plywood nailed at 150 mm centres. In any case, it is necessary to smooth subfloor irregularities with a levelling compound.
<B><font size="+1">Modes of failure</font></b>
<B>Surface wear and deterioration</B>
Cork and linoleum may not be suitable for areas where there is a risk of high-impact loads, such as chair legs and wheeled traffic, although this can be overcome by specifying toughened forms of covering that have improved resistance to point loads.
Surfaces of linoleum and PVC may break down in localised areas of heavy use, especially at entrance doors or doorways where people have to queue.
Coverings may lift as a result of a lack of adhesive or cleaning with excessive amounts of water.
Areas suffering from heavy traffic may become blistered by the unequal pressure of footsteps, which will accelerate local premature failure.
<B>Bubbling, ridging and rippling</b>
Movements in the substrate, moisture or lack of adhesive may cause the covering to ripple, bubble, lift or become detached. This can result in the covering becoming torn. Carpets may also stretch and exhibit ridging in heavily trafficked areas. Some textiles, both synthetic and natural, may shrink as they dry out; typically, backings are affected. Surface distortions may result.
Welded joints may fail due to the shrinkage of PVC flooring or inadequate weld strength.
Pine gel cleaners are known to have caused shrinkage damage to PVC flooring. The phenolic content of the pine softens and loosens the adhesion of polish films, which results in the removal of the protective surface dressing. This leads to increased wear.
Where polyvinyl chloride subfloors or polyvinyl chloride carpet tiles are used it is possible for plasticiser to migrate. If the subfloor shrinks or becomes brittle, softening or weakening of the carpet or adhesive may result.
Large static loads or impact loads may cause indentation to the floor covering.
<b><font size="+1">Durability tips</font></b>
- Ensure the substrate is thoroughly dry before laying any impervious material.
- Protect joints in coverings at heavy traffic areas, such as thresholds with timber mouldings or aluminium extrusions.
- Specify an entrance flooring system to reduce the dirt and grit carried into the building. This will reduce wear to floor coverings within the building.
- Where sheet coverings are being used, keep the number of seams and joints to a minimum. They incur extra costs and increase the number of potential weak areas of an installation, thereby increasing the risk of damage. Where seams are unavoidable, ensure the position of the seam is parallel to the flow of traffic.
- Avoid double-sided adhesive tape fixing for carpets in commercial applications, as the bond is unlikely to withstand heavy use.
- Where chairs with castors are used, ensure that the covering satisfies the castor chair test for continuous use – for carpets this is BS EN 985 or for resilient coverings BS EN 425. Alternatively, consider using an additional mat.
- Substituting tiles in high usage areas with tiles from low usage areas can reduce the whole-life cost of carpet tile installations, as it will delay having to replace tiles.
- Mid-range colours tend to show soiling less than dark or light colours, so cleaning need not be so rigorous for this range, thereby increasing the floor covering's lifespan.
- Maintenance of linoleum and PVC should take into account the principles and guidance of the British Standard on care and maintenance of floor surfaces – BE 6263–2.
- The manufacturer should supply a comprehensive operating and maintenance manual for the floor covering, which should include cleaning requirements. Define a cleaning strategy appropriate to the use of the floors – in other words, only clean when and where it is necessary to do so.