When trying to figure out if a requirement is a service or construction, a good starting point is looking at the definition of construction IAW FAR part 2; Construction means construction, alteration, or repair (including dredging, excavating, and painting) of buildings, structures, or other real property. Definition of a service falls under FAR 37.101, where a contractor is performing an indentifiable task, and includes routine recurring maintenance of real property.
Use the rules in DFARS 222.402-70 if the definitions of construction and service did not answer the question. DFARS 222.402-70, Installation support contract, is a good resource since it is important to know if there is an applicable labor law. This talks to coverage of the Service Contract Labor Standards statue and the Construction Wage Rate Requirements statute. Paragraph (d) is very helpful as it establishes parameters when it is unclear if the work to be performed falls under construction or service. Work of 32 or more work-hours falls under Construction rates and work requiring less than 32 work-hours shall be considered maintenance subject to Service Contract Labor Standards.
Looking at context of all this information, the contracting officer will need to use their business judgement to make the call.