I am trying to help an old (84) friend. I'm 75, but in pretty good shape. He has an 8 x 13 roof deck with EPDM underlayment. We had a rogue snowstorm last month with 1.5" of water. A 4" hole appeared in the drywall ceiling below the deck. The deck has one 2" floor drain . Upon inspecting and removing a section of ceiling drywall below, I found this had been leaking for years, as I saw mold on the top side of drywall and stains on the vapor barrier. The stains all pointed to the deck floor drain. Today, with the drywall removed below the drain, I put 25 gallons of water on the EPDM, expecting to see the exact source of the leak. Nothing. Not a drop of water. I am lost. Can anyone help??

 

The problem with roof leaks is that where you see the water leak coming thru the ceiling below is usually not where the leak is. In other words..... you get a leak and the water can travel along a joist and drop off at a low point.

You mentioned vapor barrier. If that's plastic the water can travel even further before it leaks thru the ceiling.

I'm not a roofing pro so I'm not sure what the best way would be to locate a leak.

 

You may need to apply water to one section of the deck roof at a time for maybe 10 minutes and check for the leak. Then move onto another section until you find the area that causes the leak. The drain is a common leak point but with a deck above it's possible the membrane has gotten punctured.

 

I have been thinking about this for a day since my water test. My test did not wet the entire membrane. Due to house settling, it slopes to the SW corner, where 25 gallons pools about an inch deep. That is enough water to reach the drain, which is no longer the low point. I am wondering about simulating Mother Nature with a small lawn sprinkler or not repairing the drywall until we get another snowstorm. I have two areas of ceiling removed, one 48"x'48 where the drywall had sagged about 1-1/4" from water over many years and a second spot that exposes the drain from below. I have inquired on my neighborhood blog if anyone has experience with Boulder roofers on such a problem. No responses yet.

 

Based on the condition of the rubber.....if it's older..... a roofing company may not even offer a repair. They may recommend replacing it.

 

This may be a mystery without any easy solution, I think you are right PJ, this rubber is 43 yrs old and just not worth extensive analysis. It is just one of those things that I thought would be easy, but it is not. How much can 90 sq ft of roof cost?