Final answer:
Lift-slab operations involve the lifting and placement of precast concrete slabs to form a structure. They must be designed by a registered professional engineer, include detailed instructions, and should only be implemented by trained professionals.
Step-by-step explanation:
Lift-slab operations refer to a construction method in which precast concrete slabs are lifted and placed in position to form the structure. It is important that the operations are designed and planned by a registered professional engineer with experience in lift-slab construction, ensuring proper safety and structural integrity. Therefore, statement 1 is true.
Contrary to statement 2, lift-slab is a commonly used method for concrete construction, especially for multi-story buildings. It offers speed and efficiency in construction.
Furthermore, detailed instructions and sketches on the method of erection are indeed necessary for lift-slab construction, as stated in statement 3. These plans and designs help ensure the proper execution of the lifting process.
However, statement 4 is false. Only trained professionals who have the expertise and knowledge should implement the lift-slab plans to ensure the safety and quality of the construction.