Things You'll Need
Deep-scan stud finder
Built to give the roof a sloped design to shed water, trusses are the studs that support the roof sheeting. On older mobile homes, where the roofs are nothing more than a covering of thin sheet metal, the lines of the support beams are clearly visible through the metal. On newer mobile homes, or older homes where the roof has been modified and covered with shingles, the roof trusses are not as easy to detect. (see reference 1 and for all steps)
Place the ladder in a secure position and location against the side of the structure at one end of the roof. Do not let the weight of the ladder rest against unsupported objects such as eve troughs or trough hangers. Check that the feet of the ladder are firmly set on stable and even ground. Wiggle the ladder gently, side-to-side, while observing the legs and feet of the ladder for stability.
Climb the ladder far enough to reach the edge of the roof. Set the stud finder to "deep scan" mode so the finder will be able to read through the shingles and roof sheeting.
Run the head of the stud finder along the top edge of the roof. The end trusses should be located at or near the ends of the roof structure.
Listen for the stud finder to "beep," signaling the location of the first truss. Place a clothes pin on the edge of a shingle, directly over the truss, to mark the location. Trusses run in a straight line from the edge of the roof to the peak.
Move the ladder down the side of the structure approximately 2 feet and locate the next truss with the stud finder. Repeat the procedure until you have located and marked all the trusses.
Wear a safety harness if you climb onto the roof.