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5 Causes of Improper Roof Installation

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To the untrained eye, it can be difficult to determine whether your roof was installed correctly. After all, we hire professionals because we put our trust in their ability to properly install our roofs. 

Unfortunately, not all roofing professionals take the necessary steps to ensure that roof installations are completed in a way that will extend the life of your roof. Some roofers cut corners to save time and help keep their invoices low. However, when the improper installation fails, those low prices can cost homeowners substantially more than they “saved” up-front. 

In our 30 years of repairing leaky or improperly installed roofs, we’ve seen that not all roofing jobs are done equally. Some of these improper installations can cause weakened shingles, water damage to the structural integrity of your roof, loose or missing shingles, and increased susceptibility to storm damage.

Issues tend to arise when a roofing contractor doesn’t have the necessary experience or skills to install your roof. We know it can be difficult to spot an improper installation, so let’s go over five common causes to help you identify a poor roofing job before it’s too late.

1. Poor Workmanship

Poor workmanship is one of the leading causes of improperly installed roofs. If your roofer used shortcuts to save time or didn’t install all of the roofing components, accessories, and materials according to the manufacturer’s installation guidelines, you could end up with a low-quality roof.

Here are some common signs of poor workmanship:

  • No starter shingles- When roofers don’t use starter shingles and install the first course of shingles directly onto the eave or rake, water channels can form across where the first course of shingles align. Moisture can then come into direct contact with the roof deck. Shingles farther up the roof are protected by the courses beneath them, which catch and divert any water that happens to drip between the edges. The first course of shingles needs the same defense from the elements.
  • Non-uniform appearance- This is something that even the average person can see. If the appearance of the roof seems off, there’s a good chance that the roofing job was done poorly. Look for awkward alignment of materials, bumps and ripples, and mismatched colors and textures. The presence of any of these things may mean that the roofer was poorly trained, inexperienced entirely, or attempting to cut corners.
  • Missing drip edge- Drip edge is a metal flashing that directs water away from the edge of the roof and helps to prevent water from getting behind the soffit edge or your home’s siding. Shingles should be installed over the drip edge at both the eave and rake edge. Without drip edge, water can work its way under the shingles and cause a leak, which can eventually cause your roof decking to rot. It can also cause water stains on your siding, soil erosion around your foundation, and the potential for a flooded basement.

You could choose a top-of-the-line roofing system and materials, yet your roof is only going to be as good as your roofer’s workmanship. If a contractor installs your roof poorly, it’s only a matter of time before you start seeing problems. Read this article to learn more about how working with a low-quality contractor could put your roof at risk.

2. Insufficient Attic Ventilation & Insulation

A diagram showing the correct way to ventilate an attic

As the uppermost part of your home, your attic is sandwiched between indoor and outdoor temperatures. When these elements clash, condensation and moisture are bound to follow. Proper attic ventilation can help you avoid this problem.

If your attic isn’t properly ventilated, your roof could fail in as little as two years. The damage caused by large fluctuations in temperature could cause leaks and other damage that could drastically shorten your roof’s life.

Proper attic insulation is also vital for roof health. For example, homeowners who live in colder climates are at risk for ice dam formation if their homes aren’t well insulated. 

Ice dams form because of the continuous melting and freezing of snow caused by heat escaping from your home. As the snow melts, water runs down the eaves until it reaches the unheated bottom edge or soffit area of your roof. Once this melted water refreezes, it becomes an ice dam.

The water that builds up behind an ice dam can cause shingle deterioration, decking decay, and water leaks in your attic and exterior walls. This damage can be avoided by simply making sure your attic is properly insulated. 

3. Improper Nailing Techniques


One of the biggest errors we find with asphalt shingle installation is improper nailing. Roofing manufacturers give specific instructions on how to fasten shingles. Unfortunately for some contractors, following those instructions seems to be a difficult thing to do. 

The two most common nailing defects we find are improper nail placement and overdriven nails:

  • Incorrect placement- When a nail is installed above the nail line on a shingle, it’s considered a high nail. High nails are hard to detect because they’re typically covered by an adjoining row of shingles, but they can cause big problems. When a shingle is nailed too high, the nail won’t penetrate the shingle below it.
  • Overdriven nails- Roofing nails have to be driven straight with the right amount of pressure to hold shingles firm. If they aren’t, water could get under the shingles and cause a leak. If it looks like your shingles have lifted, the nails might’ve been improperly installed.

4. inclement Weather

Believe it or not, weather conditions on the day of your installation can affect the outcome of your roof. If temperatures are below 40° F, it is too cold to roof a home. Roof installation and replacement require adhesive products that need the sun's heat for activation. 

However, if you live in North Carolina or a state with warmer weather, you could potentially replace your roof in the winter. While you might wake up to 20° F weather in the morning, by noon it could be 45°F+.

Two roofers on a snowy winter roof

Rain, on the other hand, is a different story. The roofing deck below the shingles is made of plywood. If the shingles are removed and the deck is exposed to rain, it will absorb water and swell. Shingles will not adhere properly to a wet deck. If shingles are placed on the deck before it’s dried completely, moisture could get trapped underneath and cause the wood to rot.

When roof decking is subject to wet weather, the deck itself can also grow mold and mildew. This growth can cause the deck’s wood to lose its shape and decrease the life of your roof. 

5. Failing to Replace Vital Components

A simulated roof with a full GAF roofing system, including underlayment, leak barrier, starter shingles, and drip edge


Some low-quality roofers will reuse components from your old roof to save time on your replacement. This is not a good practice and can lead to premature roof failure.

Not every roof is built the same. Some have unique roof-to-wall intersections and/or areas with sharp corners that are difficult to flash. Although it can be tricky, your roof’s metal flashing must be replaced during your replacement. If old flashing is reused, it’ll most likely be just a few more years before you need a new roof.

Replacing all box vents and roof boots during your replacement is equally as important. Box vents are used to help remove warm, moist air from inside your attic. During a replacement, they need to be examined for signs of rot or rust. If old vents are reused without being checked, your roof could suffer.

If your roofer isn’t replacing your flashing and box vents, chances are they’re also not replacing these vital components:

  • Ice and water shield- This is a self-adhering, rubberized membrane that protects your roof from leaks caused by heavy storms, wind-driven rain, and ice dams. It works by creating a watertight seal between shingles and the roof deck to prevent water penetration.
  • Roofing underlayment- This is a water-resistant material that lays directly on top of the roof deck. Rain and snow can get trapped under your shingles, exposing your deck and the interior of your home to moisture damage, leaks, mold, and rot. Underlayment provides an additional layer of protection that shingles alone can’t offer.

How Can I get my Roof Properly Installed?

Now that we’ve gone over what causes an improperly installed roof, you may be wondering how you can avoid an improperly installed roof. 

If you want to make sure your roof is properly installed, here’s our advice: hire a seasoned roofing contractor! With years of experience under their belt and reviews from homeowners just like you, an experienced contractor will know the best practices for a safe, long-lasting roof repair or replacement. Read this article to learn more about the benefits of working with an experienced roofing contractor. 

If you live in Raleigh and need a repair or replacement, don’t hesitate to contact us for an inspection, a free estimate, or to even ask us about our roofing techniques! With over 750 roofs worked on each year, we know how to provide the high-quality roofing service that homeowners, like you, are looking for.

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