Well engineered and properly installed two part flashing can handle this movement with no problem.
Flashing 2 roofs together.
Slide the right edge of the flashing under the highest roof pitch.
Two part flashing systems consist of a base flashing often step flashing that is laced into the finished roof material.
This is where joining two pitched roofs together starts.
The base flashing or apron flashing is the bottom piece.
Below are the steps on how to join two roofs together if they have different pitch.
At the low end of the valley the subfascias of the two roofs are mitered with a block filling in the roof framing.
Here on this roof in sheffield one roof is spanish slate and the other is man made slate.
When the roof materials naturally expand and contract with weather changes the two pieces can move so the whole system stays secure.
Now nail this first flashing at both its far ends.
Roofs peel off from the edges so it is critical to hold them tight with the roof deck sealed on the outside we turn to flashing the edges with metal and membranes metal drip edge flashing image details roofing wrb flashing.
Step 6 install the flashing.
Remember to caulk the underside of the flashing with a sealant.
There is another benefit to two part flashing.
A quick video on joining two roofs together.
Joining two roofs with different pitches.
Finish by nailing osb sheathing metal flashing metal drip edge and overlap the new shingles between two joined roofs.
Put the lumber aside.
The flashing materials will continue to be leak proof if they can withstand this movement of the roofing materials.
Next put the flashing between two roof pitches.
Slide the flashing under the highest roof pitch first and followed by the lower pitch.
Sheathing blocking is added along the valley and the sheathing pieced in for both roof planes.
Install valley battens on both ends of the roof valley then attach first flashing 3 4 inches over the roof flange and another 3 4 inches over the fascia if any is present.
Position the flashing between the two roof pitches.
