If, for whatever reason, your construction is complete but you were not provided a windstorm certificate all is not lost. There is a process that may still allow you to obtain certification on completed construction.
In this case the process is to have an engineer licensed in the state of Texas perform a post-construction inspection on the construction needing certification. This type of inspection is much more difficult for the inspecting engineer because it is much more difficult to verify that all work was done to current specifications. Any information you can provide the inspector will be helpful. Keep all of your invoices showing quantities and types of material purchased or any specification sheets or scope of work sheets provided by the contractor. Photographs documenting the sequence of the construction are also very helpful.
If the engineer/inspector is satisfied that the construction is completed correctly they will submit a form WPI-3 to the Texas Windstorm Insurance Agency (TWIA). Once TWIA is satisfied that the inspection is complete and the construction meets their standards they will issue a form WPI-8-C which is the windstorm certificate you take to your insurance company to obtain windstorm insurance for your property. The process is simple, the difficulty lies in determining the quality of the construction after the fact. It is much easier and more certain to involve the engineer from the beginning than to try to do it after the fact.