We have general structural certifications for most of our regularly stocked models to give you a realistic idea of the loads of each greenhouse. However, if you are applying for a permit you may need a letter stamped by an engineer certified by your state, or you may need a site specific certification. We do not provide these state or site specific documents, but they are avaialble for a fee. Conversely, we may be able to point you toward an engineer that can assist you with the documentation you need. Keep in mind, each location/state has different load requirements. If you are in a location that has higher load regulations, you may need to purchase additional reinforcements.