Here is some information about engineering and permits needed to build a patio cover.
In some cities, a building permit is not required for constructing a Patio Cover, check with your Building Department about specific requirements before construction. i.e. a Permit may not be required for a free-standing patio cover if it is at least 6 feet away from another building and the roofing structure (including eaves, gutters etc.) does not cover more than 300 square feet. Also, some departments do not require a permit if using a lattice (non-solid) cover.
In other cases, to obtain a permit, contact your Building Department. The department typically requires: