A roof that slopes in only one direction is called a shed or pent style. It is a common roof on sheds and other outbuildings and is frequently used on carports, patios, porches and small additions to a house. It also is often used on dormers, extensions built on a basic roof to provide more light or space inside. Single-slope roofs are easy to build and are compatible with almost any architectural style. A single-slope roof can be built with many pitches or angles, from almost flat to steep. The key to a good single-slope roof is strong framing underneath.
Use prefabricated mono trusses for the easiest and best framing on a single-slope roof. Measure the outline of the structure to be roofed with a tape measure or get dimensions from a house plan. Select an angle of slope, away from a house, into an area with good drainage and complementary to an existing house or other building. Choose a pitch and order trusses to fit the space.
Mark truss locations on the front and back wall caps of the structure. Get on a ladder with a tape measure, speed square and marker. Measure 1 1/2 inches in from one side and draw a line with the speed square to mark the location for the first mono truss. Measure 23 1/4 inches in and draw another line, for the outside of the second truss. Measure 24 inches from that line, then add 24-inch increments across the roof. Mark wall caps on both front and back.
Erect one truss in place on one side of the roof. Set it plumb with a level and brace it temporarily with boards nailed to the truss chords and to stakes in the ground outside. Fasten its bottom or joist chord, which runs between the roof ends, to the wall caps with 16d framing nails and a hammer. Drive nails diagonally through the truss into the caps, two nails on one side, one on the other.
Set other trusses across the roof and nail them in place. Nail temporary braces between trusses starting with the third truss to stabilize them. Add any required permanent bracing with boards fastened between trusses; most single-slope roofs with modest pitches will not require extra lateral braces. Remove temporary braces.
Install hurricane ties on each end of each truss. Fasten the bottom of these metal brackets to the wall caps with four 8d galvanized nails, then nail the top portions to the truss chords with four more 8d nails.