After that crazy rain and hail storm the other week, we noticed a wet spot on the floor of the rental unit.  Just what we needed right now, a leaky roof!  When we had our home inspection, the inspector did point out a few areas to keep an eye on so we were not completely surprised.  The roof is in decent condition and we have been counting on the fact that we wouldn’t need to do any major work to it for at least 2-3 years.

It looks like at some point there was a skylight in the roof that was removed and capped with a piece of plywood when the asphalt roof surface was last replaced. Unfortunately, the crew didn’t do a great job covering the old skylight. Instead of building inclines and running the complete asphalt sheets over the skylight they cut the sheet and spread flashing cement over the seams created. Over the years the flashing cement on the corners has worn down and now there is a small leak.

Lucky for us our architect came to the rescue.  He is something of a waterproofing dynamo.  On Saturday he and I took a trip to Home Depot to pick up some Karnak Flashing Cement and Cotton Fabric.

The fix was easy enough. Using a trowel we simply spread the Karnak across the top and sides of the skylight cover. We laid down the cotton fabric across all the edges–this just gives it some strength. And finally, we put more flashing cement over the tape. He recommended spreading it out away from the edged areas, “like icing a cake” in his words.

Apparently, over time the flashing cement will get harder but never completely harden. This way it can hold the seal while the building flexes between freeze and thaw cycles.

The long-term fix for this is to weld an aluminum cover for the skylight. That sounded a bit expensive but would probably last 20+ years. In the end, this cost us only about $30, 1 hour of work and it should last a few more years.  Not a bad DIY project.