The following are not intended as detailed specifications rather they are to encourage you to think about how you describe what you want.
Rather than getting into very detailed descriptions of equipment it will be preferable to state the level of accuracy required or desired. For example, you may want a car, capable of carrying at least 4 people, with an engine capacity of not less than 2L.
Rather than telling potential suppliers the number of staff and hours of work the specification should outline what is required. For example, the building X is to be cleaned before start of work at 8am Monday - Friday. There will be details of what is expected as part of the cleaning process such as bins emptied, what surfaces are to be dusted, or perhaps laboratory worktops are to be excluded. However, the tenderers would be free to develop proposals where they provide staff to complete the work at stated times between 18.00 in the evening and 08.00 the following morning.
For examples of actual specifications, please refer to Sample Documentation section.