How To Construct A Valley On A Pitched Roof

Unit run of the hip.

How to construct a valley on a pitched roof.

This type of construction involves the use of factory made frames called tresses each of these trusses includes combining the joist. Sheathing blocking is added along the valley and the sheathing pieced in for both roof planes. In a hip roof with equal pitches the unit run of a hip or valley rafter is 17 inches for every 12 inches of run in the main roof. The heel height overhang and ridge and fascia boards for both roofs will be the same.

Valley roof the valley roof option is used to calculate valleys for 90 degree intersecting roofs with equal slopes and wall plates at the same height. Another pitched roof construction manner is the truss roof method. Therefore the pitch of the valley rafter is 12 in 17. Soup to nuts riley shows the proper way of installing a valley on a roof.

For any roof slope expressed as x in 12 rise in run the hip and valley factor is determined by finding the square root of rise run 2. Of run for the valley rafter to rise the same distance that the common rafters rise in 12 in. Draw a diagonal line between 9 feet the run of the main roof on the tongue of the square and 7 feet 6 inches the secondary roof run on the blade. Part 3 of the four part guide to roof construction covers pitched roof detail.

Divide the rise by the run the run is 12. The blind valley roof can be used to calculate valleys for roofs with unequal slopes. At the low end of the valley the subfascias of the two roofs are mitered with a block filling in the roof framing. The run of the valley rafter is longer than the run of the common rafters so it takes 17 in.

Use a sturdy extension ladder that extends at least 3 feet above the eaves to climb onto the roof and secure the bottom to the foundation and the top to the eaves or fascia so it doesn t move. This gives the angle of the hip rafter. To transition the eaves the horizontal fascia extends to the last rafter tail and a vertical return finishes the transition. The hip and valley factor varies according to the slope of the roof as shown in the table below.

Roof ridges and ridge tiles roof hips and hip tiles roof valleys roof verges and lead flashings. To get the most out of it is helpful to also read parts 1 and 2.