If you're looking for shingle installation tips, you've come to the right place. But first a true story … 17 years ago, I worked for a small roofing company in Cape Coral, Florida. The boss had sold a new flat roof to a homeowner who had a leak on his lanai. The flat roof was very old and obviously needed replacement. But after one of our crews installed a new flat roof, the irritated homeowner reported that his roof still leaked in the same place.
The boss sent me out to take a look. The leak was showing up at a back corner of the flat roof, right at the base of a valley in the shingle roof. As soon as I saw it, I just knew it was a valley leak. I had seen that very same situation many times before.
Based on the location, I could not believe the boss had not sold a valley replacement along with the flat roof. I figured we would probably be stuck replacing the valley for free. But the Boss was the kind of guy who could sell ice cubes to Eskimos. He actually got the homeowner to pay for the new valley. I did the work and found that the valley metal had holes rusted all the way through it. Obviously, we had found the leak … Or so I thought. Next rain, the irate homeowner calls again. Same leak. Same place.
I went back for another look. The only other thing I see is a little dip in the shingle installation at the flat roof transition. The guys had not tapered out the floors of flat roofing very well. The shingle roof was only about 3:12 slope and I could see how a little dip like that could hold water and leak. So I reported to the boss that we had to redo the transition on our brand new flat roof. Since there was no way the homeowner was going to pay for that, we were going to have to eat that cost. So now both the boss and the homeowner were irate. That was until I did the work and it rained again. Same leak. Same place. They were not just irate any more … It had turned to rage.
The official term for leaks like that is a "head-scratcher". Over the years I've become somewhat philosophical about them. I figure they exist to teach me patience … and keep me humble! Back then, though, I was more upset than the boss and the homeowner put together. In fact, I decided that if I could not find that dumb leak, I was going to quit roofing altogether. I went back over to the house one more time and sat down on the flat roof trying to figure out where the water was getting in. We had fixed everything it could possibly be.
That's when I noticed a nail sticking out of the shingles. It was several feet over from the top of the valley … but it was right in line with the leak. The rusty nail was the same color as the shingles and automatically impossible to see when standing up. It was also so loose I could pull it out with my fingers. It only took a few minutes to repair the nail hole … and it stopped the leak. The homeowner needed a new flat roof and valley, but it was the dang nail that caused the leak.
The lesson here is that protruding nails (or "nail-pops" as they are usually called) cause leaks. In fact, they are one of the most common shingle installation problems. They typically occur when the roofer is using a nail gun and a nail fails to seat all the way. Over a period of time, the protruding nail pokes right through the shingle above it, eventually causing a leak.
To prevent it, make a habit of glancing at the nails you just installed. Keep a hammer handy and smack down any that are sticking up. Also, take a look at the roof about a month after the shingleles are laid. That will give time for the shingles to lay nice and flat. From the ground it's easy to see any shingles that are sticking up a little. Those are nail-pops. Just pop the shingle loose first thing in the morning when the shingles are cool and pound the protruding nails down.