I currently own a two-story row home that is probably close to 100 years old and was last renovated 15-20 years ago.
My big problem right now is a leak that is coming in through the roof in the back corner of my house, dripping through the wall, and into a closet that is below the leak on the first floor. In the 8 months since I have moved in, this very small leak has caused the ceiling in the closet to cave in, the dry-wall beneath the leak to get wet and disintegrate, and various water stains all around the leak.
Now, it has taken some time and crafty problem-solving but I have located the exact spot of the leak from inside the house. I have done my best to extrapolate where it would be coming in from the outside and done my best to patch up that part of the roof. Well after countless rubber coats and roof sealant in the general area of the leak (I've covered about a 3 foot by 3 foot area in the back corner of the roof above the leak with roof patches), the water is still coming in. After more inspection here is what I think is happening. Whenever the roof was last redone, instead of removing the old roof and completely redoing it, they just put the new roofing on top of the old roof (I can see from the inside of the house when I lift up the drop ceiling panels that the old roofing material is still there). What has started to happen is that the two layers of roof have separated from each other in some spots, specifically directly above where the leak is.
So here is my theory: The roof is old and water is seeping through the top layer in different places throughout the roof (not necessarily directly above the leak and probably very small micro-cracks or holes). The water then seeps through the gap between the roof layers and gravity takes it down to the back corner where it eventually goes through the leak into the house.
1) does this sound like a reasonable theory? I don't know the most about roofing but after racking my brain for months this is my best idea of what is happening and the only explanation for why my gratuitous roof patches have done nothing.
2) I know where the water is coming from the inside. If I seal up the leak from the inside, this will stop water from coming into the house but it doesn't stop the actual cause of the problem (water seeping through roof). Is this a bad idea? Will sealing the leak from the inside cause me more problems down the line?
To clarify, I don't need a permanent, professional fix. I need something that will get me by for the next 1-2 years as I intend to move within that time frame and this is what I think is the most reasonable fix given the situation. Please, if there is a better way to do this, I would love the input.