Install the underlayment as directed by the manufacturer then set the valley flashing on top of it.
Installing flashing on porch roof.
For the valley areas of the roof you will be using valley flashing.
Put on a pair of leather palm gloves to avoid injuries from the sharp edges of the metal flashing.
How to install porch roof flashing step 1.
Install the flashing place the flashing between the joint of the house and the roof.
Cut an angle with tin snips on one side of the flashing piece from an end.
Before you apply the flashing you ll need to lay down a waterproof membrane.
Nail the flashing securely in place using roofing nails.
The flashing on the wall should be flush against it and the porch roof portion should be on top of the shingles.
If you already have faulty flashing installed you.
Lay the cut flashing down at the corner.
How to flash a porch addition 1.
Measure the length of the porch roof joint to determine how much flashing you will need.