Once the design is complete and the nature of the work is known you should begin to think about the future for the piece of work and a plan for maintenance should be agreed before fabrication starts. Things to consider at this stage are:
The maintenance requirements for any particular piece will of course vary according to the nature of the materials from which it is made and where it is sited.
A painting or textile might be framed under glass or a small sculpture might be housed in a vitrine in which case only the glass may need cleaning but could be left with its surface exposed in which case cleaning might not be a job for regular cleaning staff.
Specially designed street furniture, railings etc. might be absorbed into regular contract maintenance. A large piece of external sculpture may need more specialist cleaning.
An electronic or installation piece may require maintenance of DVD players, projectors, light bulbs or perhaps computer equipment. A water feature may need to be treated to avoid build up of mineral deposits or algae.
If the work is using manufactured parts then warranties/guarantees should be sought from the manufacturers. It may be worth considering purchasing or commissioning spare parts in advance to ensure you have them in stock.
You can normally expect the artist to provide advice and in some cases even a full maintenance plan. It is good practice where possible to offer the option to the artists to undertake the maintenance but if not, then they may be able to recommend sub-contractors or outline procedures that can be undertaken as part of normal site cleaning and maintenance. Whoever does this work must have the appropriate level of insurance.
Maintenance issues should be considered early on but there is always the chance that you may not know the full picture until the work is installed.