Joining Two Pitched Roofs Together

To transition the eaves the horizontal fascia extends to the last rafter tail and a vertical return finishes the transition.

Joining two pitched roofs together.

Joining two roofs with different pitches is a method that exists in the building and construction world. Joining different flat roofs. To tie both roofs together brace the upright and draw chalk guidelines on the shingles to mark the center line of roof valleys where they both will connect. They form an upside down v with the point at the top of the addition roof.

Slide the right edge of the flashing under the highest roof pitch. Sheathing blocking is added along the valley and the sheathing pieced in for both roof planes. The other is to get the fascias to line up. Joining these two roofs poses two main challenges.

Determine where the two roofs will tie or join together. If they have same pitch then you ll only require one framing type. Position the flashing between the two roof pitches. One is getting the two differently pitched planes to meet at the hip or valley rafter.

The piece that allows us to join the two different slopes is the pitch transition trim. At the low end of the valley the subfascias of the two roofs are mitered with a block filling in the roof framing. Measure carefully to decide how many trusses that you need. We re going to install it over top of the panels that have already been installed on the lower slope.

This technique is beneficial particularly in home expansion. The overhang is 16 inches measured horizontally and the fascia runs at a continuous height around the entire house. This allows water to flow off the upper panels out over the trim onto the lower panels and exits the roof at the eaves. Cut two rafters with a circular saw to the pitch of the addition roof and nail them across the rafters on the old roof.