Jefferson County Colorado requires a Defensible Space Permit, (wildfire thinning), for all new developments in the Wildfire Overlay Zone District above 6,400 feet in elevation. This permit must be issued before submitting for a building permit. Jeffco Planning and Zoning will provide you with a list of approved Forester contractors that offer the service. They will come to the site and mark the trees to be removed. Once this is done, the homeowner needs to remove the marked trees and set up a second appointment with the Forester for a final inspection. After the final inspection, a notice will be sent to the Zoning Department to close the Defensible Space Permit.
Additions over 400 square feet also require a Defensible Space Permit, unless it is a detached garage with no living space above the structure. Keep in mind, a recreation room, study or private office above a storage space in the garage will be considered living space and will most likely require a Defensible Space Permit if it falls within a Wildfire Overlay Zone District.