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Damage Control: Avoid Common Roofing Mistakes

Cutting corners may save you time, but when you or your subcontractors stray from the rules of rooftop installation, the consequences of negligence can be pricey. Even minor oversights can cause leakage; and if your customer experiences problems later on, you could get stuck with the repair bill.

“The repair [of an improperly installed roof] can require the total replacement of the roof and cost thousands of dollars,” says Mark Graham, the associate executive director of technical services for the National Roofing Contractors Association (NRCA) in Rosemont, Ill. 

Proper installation techniques vary depending on the materials you must install and type of building you’re working on. To protect your company against costly mistakes, always familiarize yourself and your employees with the material manufacturer’s installation instructions, rooftop safety guidelines and equipment, and the correct use of all tools. 

Step One: Follow Minimum Slope Guidelines 

First, it’s crucial to pay attention to the various slopes of the roof, particularly where there are changes in grading. “A valley is one of the most susceptible areas to leakage because it sees the most runoff water,” Graham says. Valleys are also tricky because the wrong material won’t adhere properly in those areas.

To avoid problems, be sure to familiarize yourself with the roof’s slope before selecting materials. For example, if you’re installing asphalt, use a minimum slope of 4 and 12 — 4 units of rise for every 12 units of run, Graham says. “The NRCA also recommends a 4:12 minimum roof slope for tile, slate wood shakes and shingles, synthetic/fiber cement, and architectural metal panels,” he says.

Step Two: Proper Installation of All Materials

Diane Ausavich, manager of the National Association of the Remodeling Industry (NARI) Milwaukee and president of Milwaukee-based Carl Krueger Construction, says flashing issues can lead to roof water damage. She points to two common errors related to flashing, the sheet metal shaped specifically for strength and weatherproofing:

  • Improper installation: Flashing should be installed with the U-shape facing toward the valley. Also, be sure it’s layered underneath shingles rather than on top of them.
  • Insufficient securing material: If people don’t use enough caulking or fasteners when securing roofs, it can cause the valley flashing to buckle and eventually cause leaks.

Step Three: Prevent Climate Problems Like Ice Damming

Every region has its weather-related issues, particularly in northern climates where a roof can buckle under heavy ice and snow. The most common problem occurs when melted snow refreezes at the roof overhang, because it can trap water under shingles or other roof finishing layers, causing leaks through the roof deck joints and nail holes. 

To avoid ice damming, Graham recommends installing an under-layment in the roof at a projected line of three feet inside the exterior wall of the building. That will add an extra layer of protection to keep water from seeping in as it melts.

Step Four: Avoid Warranty Pitfalls 

No builder should get stuck with the bill when faulty tiles are to blame, but warranties are a fact of life for roofers. Graham offers three tips for staying within warranty:

1. Can you prove a leak wasn’t your fault? Product instructions that require nailing accuracy within 3/16ths of an inch may not be realistic, Graham says. If you’re concerned about unreasonable instructions, one way around this is to pick products that leave less margin of error, such as a slate or tile product with pre-punched holes.

2. Build relationships with manufacturers. Some builders switch manufacturers just to save a few cents per square foot of material. But building a relationship with your manufacturer can safeguard your business and save more money in the long run. 

“Some manufacturers are much more realistic in their claims handling than others,” Graham says. “Builders should be looking for manufacturers that have a track record of dealing with problems by working with customers and contractors.” 

3. Remind homeowners to inspect their roof every six months. Leaks can grow and lead to more problems if left unchecked. The sooner your customers catch problems, the less likely your workmanship will be questioned down the road.

Routine inspections could lead to more work for your business in the long run.


Be sure to join the Lowe’s ProServices LinkedIn Group to read additional content and interact with other Construction/Trade and MRO professionals.

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