Finding leaks on tar and gravel roofs is not an exact science. But once you have found them what is the next step? In most cases it is raining out or the roof is wet so you can’t put down a permanent patch. That means you have to put something onto the split or roof hole that will stop the leak and works on wet surfaces. The two most common tricks of the trade are either using a Portland cement or a Bentonite clay mixture. I choose the clay. Here’s why. They both stop the leak initially. But the cement forms and solidifies into a clump that does not change shape. So once it’s formed it stays that way. The problem being is that when it completely dries it releases it’s grip in the roof and becomes separate. Thus the leak or roof deficiency is now open again and prone to further leakage… Except it’s got a clump of cement over top of it! The clay works differently. It too does dry and somewhat release it’s grip on the roof over time but it reactivates with the next rain and turns back into the thick slurry that stopped the leak the first time. Essentially it is reusable on the same leak. But to be completely honest… you need to get that roof leak upgraded to a permanent patch as soon as possible. Don’t leave the temp patch on too long and test it’s performance abilities. We dropped some clay on a roof leak in Richmond and also in Burnaby today. This is what it looked like.