The weekend didn't result in much home improvement.... though it did result in a great deal of pulled pork from the smoker on Sunday. But, with rain impending, I had to get up on the roof this week to figure out this leaking.
Using the measurements from Google Maps that I had made last Friday, I cut a little hole in the ceiling with a drywall saw and put my hand through. After pushing aside some insulation, I struck the hatch on my first try. Woo hoo! For my Google Maps next trick, I'll be bullseyeing womp rats in Beggar's Canyon. They're not much bigger than two meters.
So in ten minutes I was on the roof. The bitumen roof is definitely getting on in years, but there were no obvious compomised areas (like broken seams) on the surface. But as I moved towards the front of the house the problem became apparent. There is a metal roof covering the front facade where the dormer windows face the street, which joins the rubber roof that covers the much larger flat surface. The rubber had completely separated from the metal, so water was easily going directly under the roofing surface all the way at the front. Roof leaks rarely manifest themselves inside the house at the same place as the leak, because the surface tension of water will cause it to run along slightly sloping horizontal surfaces until something causes it to have nowhere to go but drip. In my case, the roof leaks were mostly apparent towards the back of the house, so most likely water has been going all over the place between the roofing surface and the roof itself. I don't dare look in the attic to see what kind of shape the roofing boards are in...
I shored up the problem for now with wet-patch roof tar and asphalt mesh. Longer term, the roof will probably need replacing, and depending on how much rot has taken place, probably the roofing boards as well. But at the same time, flat roofs can often be kept limping along for years if not decades if they aren't completely falling apart. I think this one falls in the "I can get ten more years out of it" category.
Though the roofing has tiny cracks in many places from long-term sun exposure, it's still basically in one piece. With a liberal application of silver roof paint (truly, a miracle product) and a couple more gallons of roof patch to hold the big seam together, I think it will be fine for the forseeable future.