Steel Portal Frame Design and Drawing

I need a skilled contractor to design and draw a freestanding steel portal frame over my existing dwelling for a second level.

Requirements are as follows:
- Alteration of existing structure to accommodate new frame
- Use of steel as primary material
- Galvanized finish on steel frame
- Options to attach facade features to main frame.
- Also to consist of 1m cantilevered overhang.

Ideal skills and experience:
- Structural engineering knowledge
- Experience with steel construction design and drawing
- Familiarity with galvanization process
- Ability to modify existing structures into workable designs

Please provide examples of similar work and relevant qualifications.