Flow Down The Roof

Without it roof runoff flows down the wall and possibly into the wall.
Flow down the roof. Place a piece of standard metal drip edge onto a table or between a pair of sawhorses. To put it in perspective the angle of this slope would be around 30 degrees. The slope of a roof or pitch is determined by how many inches the roof rises over 1 foot or 12 inches. Intake vents located at the lowest part of the roof under the eaves allow cool air to enter the attic.
This is worst when there is a door or a window below and water can seep behind the trim. If it is reduced further the flow boundary will at first be sucked down and will continue to flow along the slope and a change from pressure to suction will occur. The metal roof forms a valley where one roof meets another. Penetrations can include plumbing and roof vents chimneys dormers or anything else that projects through the roof.
Bring a 20 foot sewer auger onto the roof. You might not notice it for years but eventually rot will destroy sheathing and framing. This valley shoots rain in a flume during our frequently heavy downpours. Crank the handle to work the head through the obstruction.
Insert the head into the vent opening and feed it down until you encounter resistance. Also look for a thin stream of water flowing down one of the rafters. Look for potential entry points like roof vents valleys loose nails and mark the area with chalk so you can examine the exterior of your roof after it quits raining. Drip edge is available at hardware stores and it is made.
Look for damp spots on the underside of your roof. They can be several feet above the leak or to the right or left of it. Numerous people have tried ideas but none have worked. This means that the rise of the slope goes up or down 8 inches for every 12 inches.
If the slope of the roof is reduced a point will be reached at which pressure on the windward slope becomes zero. Follow the water uphill till the wood is no longer wet. Turn it upside down so the lip edge faces upwards. An example for a steep sloped roof is 8 12.