We have a flat roof (very low slope) made from gravel and tar, it's a little roof over the porch of the house. When it's raining, the water leaks under the soffit on the right corner, where is the less elevated part. There was almost no water that went into the gutter. I removed the loose gravel to see what was going on and I discovered a pothole in the asphalt. I spilled water in it and the water exited by the soffit, it did not overflow over the flashing in the gutter. I noticed that the gravel was loose everywhere in the roof perimeter leaving a clear gap under the flashing and the roof membrane. I started to patch some of the big gaps with plastic cement. I finally applied a non fibrous coating over some part of the joint that has smaller gap thinking that it will do the job. Then,the liquid coating was "swallowed" under the flashing and fell in the gutter making a big mess... So my question is, should the flashing be sealed all along the perimeter, if yes, how should I do that ? Plastic cement seems to have its limits. Am I missing something? Is the water drainage is supposed to be done under the flashing to fall in the gutter and there is a problem somewhere else, like with the fascia and sheating joint ? The roof age is unknown but it is probably due to be redone. My goal is to patch it to last 2 or 3 more years because we will probably demolish this structure anyway to build something else in a near future. In the meanwhile I would like to avoid the structure to collapse or being dangerous since the wood structure may have started to rot.