Per the Engineers and Architects Regulation Act:

The practice of architecture means providing or offering to provide design services in connection with the construction, enlargement, or alteration of a building or group of buildings and the space within and surrounding the buildings. The services may include, but not be limited to, planning, providing studies, designs, drawings, specifications, and other technical submissions, and administering construction contracts. (Neb. Rev. Stat. § 81-3420)

The practice of engineering means any service or creative work that requires engineering education, training, and experience in the application of special knowledge of the mathematical, physical, and engineering sciences. The services may include, but not be limited to, planning, providing studies, designs, drawings, specifications, and other technical submissions, and administering construction contracts. (Neb. Rev. Stat. § 81-3421)

The Board has several resources available to determine if an architect or professional engineer is required. 

For new construction projects, use the New Construction Flow Chart. 

For remodeling projects/one-level additions, use the Renovation/Addition Flow Chart.

You can also find more information here. 

An organization may offer or provide engineering and/or architectural services combined with construction (often referred to as a design-build) services following the conditions set forth in the E&A Regulation Act (Neb. Rev. Stat. §81-3436.01) and Board Rule 7.4. The architect and/or professional engineer must participate substantially in aspects of the services which involve architectural and/or engineering services, respectively.

Yes, professional engineers may practice in disciplines of engineering other than the discipline noted on their seal if they have the education, training and experience to do so. If a licensee’s practice is called into question, the individual may be required to provide the Board with evidence that they are competent to practice other disciplines. If the Board has deemed a licensee not competent in an engineering discipline, they are not allowed to practice engineering in that discipline.

Review Board Rule 5.1 for more information. 

It depends on the project. The E&A Regulation Act requires professional engineers to design electrical installations on all non-exempt projects. Master electricians licensed by the State Electrical Board are authorized to “plan, layout or supervise” the installation of wiring, apparatus, or equipment for projects they are installing.