In my area I need a contractor's license in order to pull a permit. At the discretion of the inspector, they reserve the right (via ordinance) to request engineering drawings, which they usually do for most signs bigger than 4x8s. Wall mount signs often need an engineering drawing specifying the wall conditions and fastening system. Basically, anything big or which cannot be seen (hidden fasteners, below grade foundations) will need an engineer's stamp of approval.
I mitigate the engineering costs by providing my engineer with drawings already spec'd. All he has to do is review them and stamp them. Not for the feint of heart, but saves money if you can do it. You can't just say you're using 1" bolts, you need a reference showing the pull strength and shear strength from a recognized testing lab in addition to demonstrating how the wall is engineered and by what method the load will be transferred to the ground, indicating structural component sizes and dimensions.
In my area, and in many others, this is a new trend. The laws have been on the books, but seldom enforced. When asked by the inspector, I would tell him what I was doing, and we would just use experience and common sense to determine whether it was good enough. Often I would just go a steel tube size up or throw an extra 1/2 yard of concrete in the hole. The advantage of using an engineer is they can save you material costs. The disadvantage is that they can be costly, especially if they need to produce the drawings.
What really sucks is who gets to slide by and who gets nailed every time. It really pays to be nice to your inspector!
