Astm e1105 and aama 501 2 test methods are good overall methods commonly used to test exterior walls sloped glazing and shallow pitched roofs to help identify leak sources.
How to test existing roof for leakage.
Begin by locating the leak on the inside of the home.
On a nice day have a helper tap on the mark while you re on the roof.
Recaulk the corner flashing if any areas have hardened caulk.
Once you locate the source of the water mark the area.
Also look for a thin stream of water flowing down one of the rafters.
For example soak the downhill side of a chimney first then each side then the top on both sides.
Confirm that the source of the water on the inside of the home is a result of a roof leak and not due to a problem associated with other components of the home.
Water will reflect light so bring a flashlight along.
If you have an attic the easiest way to spot the leak is to up there on a rainy day.
Let the water run for 10 minutes to rule out each component from the bottom up.
Have your helper stay inside the house waiting for the drip to appear.
Start at the lowest point that the water could be entering the roof system.
Other sources of potential leaks in the home include plumbing roof scuppers roof drains hvac and condensation.
The farther you move away from where the leak is showing on the interior the more time you will have to give each component to test for leaking due to the fact that if that component is leaking the water now has to run farther before it shows on the interior.
Have one person look in the attic and one person in the home.
Then do a simple water test.
Start low soaking the area just above where the leak appears in the house.
Look for damp spots on the underside of your roof.
Replace any missing or rotted siding above the step flashing on dormers.
Identifying the true location of roof leaks in the attic.
Have a roofer go on the roof with a running garden hose.
If your roof is leaking right now go into the attic with a flashlight and some chalk to mark with while it s raining.
First have your roofer do a visual inspection for obvious areas where water could enter your home.