Or, a specifier's guide to the whole-life cost of partitioning systems. Compiled by Peter Mayer of the Building Performance Group
The main options open to a partition specifier are: brickwork and blockwork, concealed or exposed frames with sheet or panel coverings, plasterboard and panel systems. The key variable affecting whole-life costs is the damage caused through the everyday use of the building and the relocation of offices. The complete failure or deterioration of a partition system is unlikely, so cost effectiveness usually depends on whether partitions can be reused, rather then replaced.
Brickwork and blockwork have a lower initial cost but do not offer the same flexibility as relocatable partition options – such choices may be more suitable for fixed areas such as toilets, kitchens and storage spaces.
The relevant British Standard for the specification of partitions is BS 5234 – parts 1 and 2. This covers the design, installation and performance of the systems, and it puts the onus on the building owner to define the service life required from its partitions. There is an expectation that manufacturers will provide predictions of service life.
Good sound insulation will contribute to whole-life costs, particularly where partitions are relocated. Factors to consider include:
- The need for sound insulation barriers in ceiling and floor voids.
- The sealing of gaps at junctions to make them airtight.
- The need for doors to have adequate mass and a good seal with the frame.
Use relevant parts of BS 8233:1999, the code of practice for sound insulation and noise reduction in buildings, for specification of performance and detailing. Clause 8.4.4 refers to partition walls.
On average, one-third of office staff move or change their workstations every year. Not all movements will require the relocation of partitions, but if they do, they may involve a substantial cost. The best estimates for the extent and frequency of relocation of partitions can come from a combination of historic data and an assessment of the future development of the office layout for each organisation.
Paper wallcoverings and emulsion paint finishes are prone to damage by adhesive materials such as sticky tape. Suitable display or noticeboard areas can help discourage informal provision of fixings and consequent damage.
Imperfections are more noticeable on gloss finishes. Specify a matt finish or textured or flecked finishes that are more tolerant of minor imperfections.
In areas where accidental damage is a high risk – say, near the post room – design to minimise the risk or provide additional protection:
- Avoid narrow corridors
- Allow for wide doors
- Include extra protection of corners with corner guards
- Protect partitions from trolleys with buffer rails or protective finishes.
Ensure that partitions have adequate strength for additional loads for example; hooks, wall-hung shelving, handrails, wall-hung units, work surfaces and basins.
Check that the partitions will not delaminate or deteriorate in the temperature and humidity levels of the office.
<B>Factors affecting durability</b>
For all systems, moisture and physical damage are the key considerations – high moisture levels will lead to physical deterioration of the partitions.
Specify a system suited to the anticipated category of duty. If a medium-duty partition is used in a circulation area, its repair and maintenance costs will be increased.
Frequency of relocation – the more a relocatable partition is moved the higher the risk of damage and the less of the system that can be reused.
<B>Modes of failure</b>
For all systems, failure that occurs will be due to dampness, water leakage or mechanical damage.
<font size="+1"><B>Brickwork and blockwork</b></font>
Brickwork or blockwork partitions, with a wet plaster system or drylining, are typical options. Blockwork is the more common choice.
<B>Whole-life cost issues</b>
Fresh blockwork is prone to shrinkage, especially if the blocks have been exposed to moisture while stored on site. The cracking of finishes as a result of shrinkage is common and incurs repair costs.
Where solid partitions are relocated, the whole-life cost model assumes that partitions are demolished and removed, and a new partition built from new materials.
- Use weak mortar, such as 1:1:5 to 1:2:9 cement:lime:sand mixes, which will cope with drying shrinkage and distribute the stresses. Alternatively reinforce bed joints, especially at junctions with steel mesh.
- Use plasterboard on dabs to prevent the finish cracking.
- Autoclaved aerated lightweight blocks are most prone to shrinkage.
- Include movement joints at 6 m centres and within 3 m of returns.
<font size="+1"><B>Concealed frame and sheet</font></b>
Here, the framing structure of the partition is concealed by the sheets or boards. A traditional system comprises timber studs with a lath and two-plaster finish. The tendency for timber to shrink, however, may cause cracking so drylining is preferable.
Light-gauge mild steel-framed partitions are becoming popular. Sheeting options include particleboard, metal-faced panels, plywood and fibreboard.
The maintenance of surface finishes can be a high-cost item as a decorating cycle relating to paint or wall coverings is required.
Costs for the relocation of stud and sheet partitions assume reusing 90% of the framework. The existing plasterboard will be disposed and new materials used.
- Where timber studs are used in kitchens or toilets with a risk of water damage, specify timber to a higher standard of treatment.
- Use regularised timber to give a truer surface for fitting sheets or boards.
- Specify materials, workmanship and installation to the relevant sections of BS 8212 for drylinings.
<B>Exposed frame and sheet</b>
Costs for the relocation of frame and sheet or panel partitions assume reusing 90% of the framework and prefabricated panels. Where plasterboard has been used, this will be disposed of and new materials used.
Two options are available:
- Gypsum wallboard panels comprise two sheets of plasterboard bonded by a lightweight cellular core.
- Laminated plasterboard comprising three or more layers of plasterboard bonded together on site.
- Costs for the relocation of plasterboard partitions assume complete replacement.
Panels are prefabricated "monobloc" structures that allows for efficient relocation without substantial repair. Panels are usually plastic or steel-based. Plastics options includes laminate or a core with a vinyl face. Steel panels are pressed; they may be single or double skin, finishes as for framed panel systems. Strength is provided by the infill, backing material or welded ribs.
Costs for the relocation of panels assume 90% reuse.
Double-skin steel panels may be prone to corrosion if condensation takes place inside them. This can be minimised by treating the inside surfaces with alkyd (plastic-based) paint during manufacture.