Building Performance Group's guide to building components' lifespans and life costs tackles domestic kitchen units.
Repairable units

Fully repairable kitchen units and worktops complying with National Housing Forum/London Housing Consortium specification (K1 programme). Units tested to BS 6222:Part 2 strength designation H and finishes tested to BS 6222:Part 3. Moisture-resistant chipboard type P5 to BS EN 312. All panels lipped in PVC. All elements of the units individually replaceable without disassembly of the unit.

Capital cost £776/kitchen

Net present vaule for 60-year period £939/kitchen

Service life 30 years

Fully repairable kitchen units and worktops tested to Furniture Industry Research Association Gold standard and/or Kitemarked to BS 6222:Part 2 strength designation H. All finishes tested to BS 6222:Part 3. All elements of the units individually replaceable without disassembly of the unit.

Capital cost £589/kitchen

Net present vaule for 60-year period £939/kitchen

Service life 25 years

Standard Units

Units tested to BS 6222:Part 2 strength designation H. Chipboard to BS EN 312. All finishes tested to BS 6222:Part 3

Capital cost £776/kitchen

Net present vaule for 60-year period £1131/kitchen

Service life 20 years

Units tested to BS 6222:Part 2 strength designation G. Chipboard to BS EN 312. All finishes tested to BS 6222:Part 3.

Capital cost £697/kitchen

Net present vaule for 60-year period £1253/kitchen

Service life 15 years

Factors included in whole-life cost over 60 years

Capital cost; installation cost; replacement of units at the end of their service lives. Costs are discounted at a rate of 6% a year. Costs are based on units for a kitchen with a volume of 2.25 m3 and on a bulk deal of 20 dwellings for a site in north London. Maintenance: none. Costs are derived from quotations supplied by several manufacturers. It should be noted that quoted prices for kitchen units vary considerably and are often driven more by appearance than by the technical specification.

Factors affecting durability

Moisture resistance of particleboard

Swelling of particleboard carcass and door materials is a common cause of failure in domestic kitchen units. Most units are manufactured from grade P3 chipboard to BS EN 312, which has a low moisture resistance and relies on the decorative surface to keep moisture out. Grade P5 chipboard, which has much better moisture resistance, is recommended for heavy-duty applications.

Strength of unit

The British Standard for domestic kitchen units (BS 6222) defines two strength levels: level G (general domestic) and level H (heavy-duty domestic). Level H units are better able to withstand heavy use and abuse, and should be specified for hostels, shared kitchens and other applications where misuse is likely.

Surface protection

Most carcasses are made from melamine-faced chipboard. Doors and drawer fronts may be made from MFC, chipboard or MDF with a decorative facing of melamine laminate, paper, thermoplastic or PVC foil. The surface layer provides the main defence against moisture damage to the board materials. Consequently, any damage or peeling of the surface layer can result in swelling and deterioration of the board. Thicker edge lippings, such as 3 mm PVC strip, are more durable than thinner laminate or paper foil edgings.

Hinges

Hinges, in common with unit carcasses, are available in two strengths. So, 170° opening hinges are less susceptible than 90° hinges to accidental damage because doors are forced open.

Drawers

Drawers are also subject to BS 6222 strength testing.

Repairability

A number of manufacturers have developed "repairable" units in which the carcasses are constructed so individual panels that get damaged can be replaced without having to discard the entire unit.

Modes of failure

Moisture-related damage

Delamination of surface finishes leading to swelling of base materials is a common mode of failure in domestic kitchen units, particularly at worktop and door edges. The risk of damage is minimised by using moisture-resistant chipboard, thicker edge lipping to doors and by selecting worktops with protective sealing to the front edge and underside.

Hinges and drawers

These are particularly vulnerable to damage from accidental overloading (such as users supporting themselves on them when opening cupboards) or misuse. Accidental damage such as the pull-out of hinge fixings because a door is forced is

a common problem, and is best overcome by using 170° hinges. Use of weaker plastic drawers is best avoided in heavy-duty applications, such as shared kitchens or student accommodation.

Heat-related damage

Some surface laminates and door materials are damaged by high temperatures and should not be used next to cookers or other heat sources. Compliance with BS 6222: Part 3 should be checked.

Durability tips

  • Ensure that all exposed edges of carcasses and worktops are properly sealed against moisture, including edges cut on site.

  • Always specify BS 6222 grade H units for hostels and sheltered accommodation where heavy use is anticipated.

  • Units that are Kitemarked to BS 6222 or that have a Furniture Industry Research Association Gold Award have undergone independent performance testing and are likely to be of good quality.

Asphalt roofing clarification

In our previous article on flat roof coverings, asphalt roofing was assigned a net present value of £100/m sq over a 60-year period. This figure assumed that the asphalt was protected with a solar-reflective paint finish that requires recoating every three years. The Mastic Asphalt Council has pointed out that many asphalt roofs are constructed as inverted roofs and require no maintenance. These roofs have a net present value of £28/m sq for standard asphalt and £32/m sq for polymer-modified asphalt, which compares favourably with polymeric and built-up bitumen membrane systems.

Further information

The Housing Association Property Mutual's Component Life Manual, written by Construction Audit, the technical audit arm of Building Performance Group, provides insured lifespan assessments for more than 500 building components. It is updated twice a year to reflect industry feedback and changes to standards and codes of practice. Published by E&FN Spon, it is available in loose-leaf format, price £175, or on CD-ROM, on 01264-332424.

The BPG Building Fabric Component Life Manual is now available from E&FN Spon, in loose-leaf and CD-ROM formats. The BPG Building Service Component Life Manual will be available in spring 2000.

BS Handbook HB 10141: 1997: Buildings – Service Life Planning: Part 1: General Principles is available from the British Standards Institution on 0181-996 9000.

For further information, contact Gary Moss at BPG on 0171-240 8070.