13.03 Operating characteristics

Categories: Durability

Introduction
Operating characteristics relate to the effect that usage has on materials and components.  They will determine the life of many components, both static components through mechanisms such as vandalism and moving components as a result of wear.  This Section describes some of the operating characteristics that should be taken into account when designing or assessing the life expectancy of a facade.
 

Impact
Impact may occur as part of the operation of a poorly-adjusted component, for example a stiff door or window which might be struck with the hand to encourage opening or closing.  Impact also occurs if a door or window opens or closes too freely and slams against an end-stop.
 

Vibration
Vibration may occur as a result of some processes within the building, for example machinery which is pushed up against a wall, or could be induced by the wind or other external sources such as traffic.
 

Vandalism
Vandalism can occur as a result of frustration generated by poorly-operating components, but can also occur for other reasons, including ‘because it’s there’.
 

Frequency of operation
The frequency of operation must be appreciated - a door which is designed for frequent use may not receive the required maintenance if used in a location where it is rarely used, and could actually be less durable as a result.  This is an area where the product should be closely matched to the expected use, to properly justify the maintenance costs and so ensure that the maintenance will be carried out.
 

Ease of operation
Hardware which is poorly adjusted and so becomes stiff to operate is likely to wear more rapidly than properly adjusted hardware.
 

Type of usage (building use)
The use of the building has an influence on the durability of components - change of use is also important, but often neglected.
 

Maintenance
Maintenance plays a key role in extending the life of the facade, but can also shorten the life of the facade.  A number of agents are possible as follows.
 

Cleaning materials
Cleaning materials may contain aggressive chemicals or abrasives and should always be used according to the instructions of the facade supplier. Where possible, trials should be carried out in inconspicuous areas before general use. Care should also be taken to ensure that adjacent materials will not be damaged.
(see BRE Digest 280 (1983) Cleaning external surfaces of buildings and BS 6270:Code of practice for cleaning and surface repair of buildings. Part1: 1982: Natural stone, cast stone and clay and calcium silicate brick masonry, Part 2: 1985: Concrete and precast concrete, Part 3: 1991: Metals).
 

Access to facade
Access to the facade is essential if maintenance is to take place.  However, access may be limited by design features, and some forms of access may permit cleaning but not maintenance (for example abseiling is fine for window cleaning but would not be suitable for replacement of a failed glazing unit). Fittings may need to be removed to gain access for inspection, maintenance or cleaning and frequent removal of items may lead to loosening or damage.

The CDM regulations place a duty on the designer to consider safe means of carrying out maintenance work. ( See BS 8200:1985 cl 39).

Access methods are described in Section 03.02.
 

Access to component
Many components are protected by their design, and so cannot be easily accessed for inspection or maintenance.  A typical example is a window incorporated into a curtain wall where the hardware may have been adjusted before installation but once installed the curtain wall frame prevents access to the hardware for inspection and lubrication, even with the window fully open.
 

Damage during maintenance
Damage can occur during inspection, cleaning or maintenance.  Typical examples are impact of cleaning cradles against glass or thin metal surfaces and sharp edged or abrasive tools leading to damage on some parts of the facade.
 

Incomplete or inappropriate repairs
Repairs are often carried out to treat the symptoms of deterioration without treating the cause of the deterioration. This can lead to premature failure of the repairs but can also lead to more severe deterioration of the structure. An example might be the application of a rendering to improve the appearance of a brick wall which then prevents moisture from escaping leading to sulphate attack.
 

Maintenance programme
The way maintenance is planned and carried out (or not carried out) will affect the durability of the façade. Maintenance may either be required on a routine basis such as cleaning and repainting or as a result of the occurrence of defects. Failure to plan for routine maintenance may lead to delays and consequently degradation of the materials. A regular inspection programme may allow defects to be identified at an early stage before serious deterioration has occurred. Failure to carry out maintenance on one material or component may lead to deterioration of other components, for example failure to seal leaks may allow water ingress leading to decay of internal timber.

Routine maintenance may include:

• Cleaning
• Repainting
• Lubrication of moving parts
• Replacement of seals
• Repointing