The Installation Mistakes That Cause Roofs To Fail After One Season

There’s nothing quite like the peace of mind that comes from investing in a brand-new roof. It looks clean, it holds up during storms, and for a little while, it feels like the house is invincible. But fast-forward a few months, maybe a year, and things can start to unravel. Shingles go missing, water finds its way in, and suddenly that top-dollar roof job isn’t holding up the way it should. And while the materials might have been top-notch, it’s the installation itself that often turns out to be the weak link.

A roof doesn’t fail in one season because of bad luck. It fails because of mistakes—some hidden beneath the surface, some barely visible but just as costly. The real problem? Most homeowners don’t spot these issues until it’s way too late.

Where Flashing Goes Wrong

Flashing may not be the flashiest part of a roof, but it’s one of the most important. This thin layer of metal—usually tucked around chimneys, valleys, and vent pipes—is there to keep water from slipping into joints and crevices. When it’s installed correctly, it guides water away from the most vulnerable parts of your roof. When it’s done poorly, though, you might as well leave the door wide open for leaks.

The trouble starts when roofers rush through the flashing work. They might skip sealing edges, use the wrong type of flashing, or fail to tuck it properly under shingles. In some cases, they’ll reuse old flashing to save a buck. It might hold for a season or two, but after that, the deterioration starts—and water’s relentless. One small gap is enough for rain to trickle in, rotting wood underneath and staining ceilings inside. What makes matters worse is how sneaky these leaks are. By the time they show up indoors, the damage behind the walls or under the decking has already done its job.

Nail Placement That Spells Trouble

Roofing isn’t just about laying down shingles and calling it a day. Every nail plays a role. You’d think it would be straightforward—hit the nail in the right spot, drive it to the right depth—but this is where a lot of installation shortcuts come back to bite.

When nails are driven too high or too shallow, or worse, placed inconsistently across the roof, they compromise the entire system. Shingles rely on precise nailing patterns to stay secure in wind and rain. Misplaced nails can let shingles lift or blow off entirely, especially after a season of freeze-thaw cycles and gusty storms. Overdriven nails might punch through the shingle itself, weakening the bond. Underdriven ones won’t anchor anything properly, and they can pop up, puncturing the shingles above them.

A properly nailed roof feels solid, like a single piece. But when the nailing is sloppy, the whole system becomes vulnerable. One strong storm or prolonged wet season is often all it takes to start peeling things back.

The Hidden Danger Of Weak Decking

Underneath the pretty exterior of a new roof is the roof decking—the foundation of the entire structure. It’s what the shingles and underlayment rest on, and it’s supposed to provide a stable, sturdy surface. But if that wood is soft, warped, or rotting, no amount of high-end shingles can make up for it.

This is a common trap during roof replacements. Contractors may focus on the visible surface and avoid checking or replacing the decking. In some cases, they might spot weak sections and choose to ignore them to cut down on time and cost. After all, the shingles will cover it up, and things might look great for a while.

The problem comes when that soft decking starts to sag under pressure. Shingles don’t sit right on warped wood, and that can lead to pooling water, more leaks, and premature aging of the entire system. The roof becomes a ticking time bomb. It’s frustrating because this is something that should be caught during installation—but isn’t.

Poor Planning, Poor Performance

Sometimes, it’s not one glaring error that causes a roof to fail early—it’s a mix of small oversights and bad decisions. Maybe the installer skipped ice and water shield in key areas, or they didn’t properly ventilate the attic space, leading to trapped moisture. Maybe the valleys weren’t reinforced properly, or the drip edge was installed backward or not at all.

These things don’t seem like much during the install, especially to someone not in the industry. But they snowball quickly. A roof is a system. When one part isn’t doing its job, the others have to work harder, and they usually can’t keep up. Even the best materials in the world can’t perform the way they should if the installation cuts corners.

This is why roofs that should last 20 or 30 years can start falling apart in 12 months. It's not about product failure—it’s about human error, misjudgments, and rushing a job that should be done with patience and precision.

Catching Problems Before They Cost You

There’s no denying it—most roof problems start the moment the installation is done wrong. You won’t see the issues right away, and that’s the hardest part. Everything looks polished from the outside. But the real trouble is what you can’t see until water starts dripping or shingles start shifting.

That’s where Sherlock Home Inspection Service comes in. We look past the surface to find what’s hidden—whether it’s flashing that wasn’t sealed right, decking that’s too soft to support the structure, or nail work that’s destined to fail under pressure. We know how to spot the little things that turn into big repairs, and we make sure our clients understand what they’re really dealing with.

If you're wondering whether your roof installation was done right—or you're just getting started and want to be sure it will hold up for more than just a season—it's time to contact us. Sherlock Home Inspection Service is here to help you make informed decisions before costly problems show up. Let’s get ahead of the issues together.