How to Add a Shingle Roof Over a Metal Mobile Home Roof

A new roof with gable ends can give a mobile home new life
A new roof with gable ends can give a mobile home new life (Image: roof image by Christopher Meder from Fotolia.com)

Older mobile home roofs often develop so many leaks that the only solution is to build an entirely new roof. While challenging, this task is not as daunting as it might seem and can prevent further damage to the home.

Things You'll Need

  • Circular saw
  • Cordless drill with Phillips head and hole saw
  • Level
  • Electronic stud finder
  • Claw hammer
  • Ladder
  • Tin snips
  • Utility knife
  • Chalk line
  • Dimensional lumber for wall plates, rafters, ridge, fascia, soffit and rake
  • Plywood
  • Siding
  • Fasteners (deck screws, roofers and nails both plain and galvanized)
  • Ice barrier
  • Drip edge
  • Shingles
  • Ridge, soffit and gable vents

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Building the roof

Contact the building inspector to obtain a building permit and determine code requirements for framing materials, spacing and roof pitch. The measurements given in this article are intended only as a suggestion and must be adjusted as local codes require.

Next, determine how much material is needed. For the wall plates, measure the length and width of the home and multiply each by two.

Rafter length can be determined using the Pythagorean theorem. A roof pitch that rises 5 inches for every 12 inches of run, for example, makes a right triangle with the third side measuring 13 inches. On a 12-foot-wide mobile home, this formula would yield a rafter length of 78 inches. Add an extra foot to allow for overhang. Building codes determine the amount of space between rafters. Use this to determine the number of rafters needed. Remember, this total must be doubled to account for the other side.

Collar ties are also needed; one-half the house's width is sufficient for each tie. To determine ridge board length, simply measure the length of the house, then add the amount of overhang desired. Fascia is the same length as the ridge, but will be needed on both sides. Rake board length is equal to one rafter's length multiplied by four. For soffit, the same length applies, but lumber width depends on the amount of overhang desired.

The amount of shingles, plywood and ice barrier needed are determined by the square footage of the roof surface, using the length of the ridge and rafters. The surface area of the gable ends is triangular, and can be determined with the formula 1/2 base x height.

Building codes determine the space between gable studs. Use this to determine the number of studs needed. Use the roof's height as the length needed for each stud; this overestimation allows margin for error.

Attach the wall plates by screwing them into the rafters of the existing home, which are located with the stud finder. The plate surface must be level, so wood wedges may be needed to compensate for the existing roof's curvature. Mark the plates to ensure uniform placement for each rafter. The nails or screws used to fasten each rafter to the plates and ridge are also determined by the building code.

The rafters need bird's mouth cuts so a flat surface will rest on the plates. These angles can be determined using the calculator listed in Resources below. Make sure rafters meet the end of the house evenly on each side so the gable siding can wrap over the existing home. Each pair of rafters must also be joined with a collar tie. Cut gable end studs from the remaining lumber and nail them into place.

Fasten plywood using nails or screws, depending on code recommendations. Vertical edges of the plywood sheets should always meet in the center of a rafter. Remember to stop the plywood one inch short of the ridge to allow for ventilation. Now the fascia and rake can be fastened (with galvanized nails for a clean appearance), and the drip edge installed.

Cover the entire surface with ice barrier before shingling. Nail shingles row-by-row from the bottom up. To keep rows even, make a chalk line every several courses by measuring up from the bottom. Once the ridge is reached, the vent can be installed.

Before covering the gable ends, cut an opening in the plywood for the gable vent, the size of which is determined by building codes. Now nail the sheets in place, and the siding and gable vent can be installed.

To provide a surface to which soffit can be fastened, scrap wood must be nailed to the wall parallel with the rafter. Use a chalk line to keep this surface even with the rafter. Drill soffit vent holes, then install the soffit using galvanized nails and add the vents.

Tips & Warnings

  • There may be bends in the lumber used for rafters. If so, crown the rafters upward so gravity will work to straighten them.
  • Important: Dimensions for materials are given only as recommendations and should not be used without first checking local building codes. Codes vary by location and may require different materials or dimensions.
  • This project will require assistance.
  • - This project is only suitable for a mobile home whose walls are resting on a foundation. If the home is resting only on its frame, additional weight on the roof could cause the floor to buckle. In this case, a roof can be built on posts driven into the ground independent of the home itself, but this task is best suited for a professional contractor.

References

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