Have a roofing expert conduct an inspection of your roof system.
Water leaking from roof through window.
These air channels will eventually cause water to come down through.
In this case you have a problematic window.
Leaks can also occur when rainwater enters through the roof chimney or loose fitting siding.
Missing shingles or a failing roof system might be your culprit.
Dormer walls provide lots of spots where water can dribble down and enter the roof.
Use enough water to mimic heavy rains.
Often wind driven rain comes in from above the roof especially around windows between corner boards and siding and through cracks and knotholes in siding.
7 rarely a leak at an overlying window or vent or a roof leak or a leaking overhead water or hydronic steam heating pipe getting into the wall and running down into the wall till it hits the underlying window running down around the frame and leaking out at the the bottom sill.
If none there then that leaves you with the dormer roof and flashing the window itself or siding above the window which are more likely unless you have a flat topped dormer.
In this case it means that the water is entering your home through an opening in the wall.
Water doesn t always come in at the shingled surface.
The most common way of sealing windows today is with the use of expanding foam.
The water will leak along the window and will pool either at the bottom or top part.
The water oozes into your house from every angle and crevice around the window from top to bottom.
If a main roof or flashing leak running down and exiting at the window you should see water running down the underside of the sheathing and staining.
The leak can also happen at the frame of the window itself.
Roof and or wall leaks window leaks can result from a structural failing elsewhere in the home such as an opening in the roof upper floors or siding.
Begin soaking low on the roof just above where the leak is visible inside the house.
Often the water will follow an unusual path along ceiling joists or wall studs until it reaches a window frame where it can then drip inside.
Run water over the low side of the penetration for several minutes while the helper watches for any water droplets.
The culprit is often old or poorly done window sealant.
In milder cases of this type of leak you may only see water come in from a few spots such as the sides or the bottom.
Sometimes leaking water is finding its way into your through your window sills or frame but is actually coming from your roof.