Learn These 7 Rookie Roofing Mistakes Before Tackling Your Roof Project

Scott Dylan Westerlund
Reviewed by Ami Feller
Updated March 1, 2022
Gray house on green lawn
Photo: Iriana Shiyan / Adobe Stock


  • Sourcing quality, new roofing materials is essential

  • DIY roofing missteps can be dangerous and costly

  • It’s worth it to check your attic's ventilation

  • Don’t neglect your flashing

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While it may be tempting to take on a DIY roofing project, a botched roof job can really wreak havoc on your home. A roof gone wrong can really wreck your house. Roofing mistakes can lead to leaks, mold, mildew, higher electrical bills, and blown-off shingles. Before embarking on a roofing project, learn these seven rookie roofing mistakes to avoid.

1. Scrounging for Shingles

While you may think you're getting a deal by reusing shingles or buying from second-hand sellers, you're actually setting your roofing project up for big problems.

Asphalt roofing is manufactured in batches. As a result, failing to use a consistent dealer will leave you with mismatched shingles that create an odd-looking roof. You may also miss out on manufacturer warranties if you aren't installing a coherent roofing system as intended.

“If you are doing a simple repair, getting a matching shingle can be tricky,” says Ami Feller, owner of Roofer Chicks in New Braunfels, TX. “If you are doing it yourself, you can take a sample of what you have to a local supply house. Even then, it probably will not be an exact match.”

It’s also worth remembering that shingles can dry out and become brittle over time. So a pack of shingles that’s been hanging out in your garage for the past 10 years might not be the best choice.

2. Layering New Shingles Over Old Shingles

Don’t install new asphalt roofing over old asphalt roofing. While there are some roofing systems that can be applied over an existing roof, this isn't the default.

It's actually illegal in some places to install a new asphalt roof without removing your old one. The problem with just laying new shingles over old ones is that you could be covering up a problem without even realizing it.

It’s wise to bring in a roofing inspector to spot weak points or fragile areas during that opportune time when the shingles are off.

Another big issue with layering shingles is that they can add unnecessary weight to your home that can actually compromise your roof structure and walls.

3. DIY Without Proper Knowledge

Nobody wants to create new roofing problems with uninformed or improper installation. There's a reason why roofing contractors go through training, apprenticeships, and certifications before they're allowed to touch your roof. Roof installation is hard, complicated work that impacts the integrity of your home's structure.

Each roofing manufacturer uses very specific regulations regarding how their roofs should be installed. Roofing pros know about warranty information, correct flashing techniques, the right number of nails per shingle, and other necessary installation details.

Installing a roof on your own doesn't guarantee that you're actually installing a roofing system to reach its maximum lifespan. There's also a chance that your warranty will be voided if you've failed to follow manufacturer guidelines to perfection. 

Before you decide whether to take on a roofing project on your own, it’s smart to get a quote from a roofing contractor near you.

4. Neglecting Your Attic

Check in with your attic when you install a new roof. Good attic ventilation is one of the keys to prolonging the life of your new roof. Poor ventilation causes shingles to wear out prematurely. It's easy to have a ventilation expert come in to run a test to let you know how your attic is performing.

5. Assuming You Don’t Need Permits

Most cities and towns require a permit for all roofing jobs. Most people don't think about permits when doing DIY jobs because they're used to contractors taking care of that detail. You may be stuck with ramifications like fines, removal of your newly installed roof, or a loss of home insurance if you fail to pull the proper permit.

6. Forgetting Contractor Insurance

Worker installing shingles on roof
Photo: brizmaker / Adobe Stock

The perk of doing your homework to find a reputable roofing company is that the crew will show up with documentation of an insurance policy that gives you peace of mind. When proper contractor insurance isn't in place, you could be responsible for paying for property damage that occurs during your project.

7. Using Recycled Flashing

Flashing accounts for just a small sliver of a total roofing project. However, its importance is immense. Bad flashing is one of the biggest causes of water damage in homes.

Don't assume that flashing is good for a second round just because it looks fresh. When possible, contractors should always install new flashing to ensure that it will last as long as all of the other new roofing materials that are being applied during a roofing job.

“However, if the flashing is behind the siding or rock work on the home, replacing it might be cost inhibitive and even detract from your home’s aesthetics,” says Feller. “This is a great conversation to have with your contractor—ask them how they are going to handle the flashings, especially on sidewalls, headwalls, chimneys, and skylights.”

Flashing is a metal that's used as a protective barrier for your roof against water intrusion. It is the defensive line between your roof and serious water damage caused by leaks that leads to rot and mold. Flashing works by suspending the flow of water away from your home to keep it from absorbing into your roofing and underlayment.

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