Back Button

How to Build a Trailer Roof

Danica Sorber

Doing a “roof-over,” or putting a pitched roof on a trailer which already has a metal roof, may seem odd but it really can be beneficial. Traditional trailer roofs require periodic maintenance and can develop problems in very rainy or snowy areas.

Building a trailer roof is challenging but worth the work.

Being metal, they are loud when it rains, and are often not well insulated, which can be both uncomfortable and expensive. A pitched roof is not only more attractive, it handles the weather better, can save energy dollars and requires comparatively less maintenance.

  1. Make sure that a pitched roof is allowed in your mobile home community.

  2. Obtain necessary construction permits by contacting your county’s building inspection department or building commission.

  3. Learn local building code regulations for the materials you should use. These should also be available at your local building commission office.

  4. Make sure the current trailer roof is clean and level, and that it is in good repair and can therefore support the weight of a new roof.

  5. Measure your home’s roof (length and width).

  6. Draw up plans for your rafters, including measurements. The more specific the plans, the better your project will be.

  7. Nail two-by-fours around the perimeter of the mobile home roof; this is known as a “wall plate.” Make sure your nails will reach through the original roofing material and into the home’s original plate.

  8. Caulk over the nails in your plate to cut the risk of condensation problems.

  9. Build your end rafters on the ground, making sure they are true and level. Your rafters will be triangular with a vertical piece of lumber in the center for support. Remember, each rafter needs to be identical. Use your level to make sure the horizontal pieces are level, and the square to make sure that the angles measure the same. The center, vertical support should be perpendicular (a 90-degree angle) to the bottom of the rafter. The sloping parts of your rafters should all have the same angle of slant.

  10. Attach the two end rafters with stringers to make what is known as a “ridge pole.”

  11. Cut the rest of your rafters on the ground, making sure each is identical to the others. You will need to cut your rafters at an angle that will allow them to rest perfectly on the ridge pole. Cut a notch, known as a “bird’s mouth,” at the point where the rafter meets the wall plate, so that it fits the wall plate perfectly. Allow for approximately 18 inches of overhang to help with rain run-off. The number of rafters you need will depend on the length of your roof and the local building code’s spacing requirements. You can expect to place your rafters every 12 to 14 inches apart.

  12. Hang your rafters using rafter hangers, seismic anchors or the method prescribed by building code. You’ll simply screw the anchor into the rafter using a drill. In some areas you may be required to use two seismic anchors.

  13. Place insulation and vapor barrier following manufacturer's instructions, leaving a few inches between the old and new roof to allow for circulation. Wear gloves, long sleeves, long pants and a face mask when working with insulation.

  14. Nail plywood sheathing to the rafters; cut out spaces for roof and plumbing vents.

  15. Staple roofing felt to sheathing.

  16. Lay the shingles or tiles, beginning at the bottom and overlapping as you go up. Nail on using roofing nails. Make sure that your shingle line is straight before adding the next layer.

  17. Tip

    Roofing is not a one-man job; find some capable friends to help -- the more the better. Budget for this project; remember, home improvements are generally more expensive than you’ve planned. If your home’s original roof is in poor shape, you may need to replace the metal roof before you can add a pitched roof. You can find roofing software online to help with producing plans and calculations. Use cordless power tools.


    If you have no experience with carpentry, hire a contractor or work only with friends who are experienced carpenters. Use all safety equipment and follow safety instructions when using power tools. Wear shoes around the work site and keep children away at all times. Pick up nails, staples, and other construction debris when you are finished.