How do shingles work?

 The humble shingle is one of the most common roof materials in the United States. It can be seen everywhere from sunny California to the chilly Maine coast, from the baked desert of Arizona to the rainy forests of the Pacific Northwest.

But what makes it actually work?

When you look at a shingle roof, it doesn’t look like it would shed rain and keep out the elements well. After all, it’s not one single, continuous surface—there are plenty of places for water to leak down into the cracks.

The reason it doesn’t is the secret of a shingle roof: it’s not just the shingles. A well-made roof is a system, not just one material. Here’s how it works.

The three parts of a shingle roof

A shingle roof is made up of three distinct systems, each of which provides a crucial part of the overall structure.

1. Decking. The decking is the material that goes on top of the rafters or trusses of the home and provides a stable foundation for the roof. It holds the roof together and supports the underlayment and shingles. Most modern homes use plywood or OSB as decking, but on older homes 1×6 and 1×8 boards are a more common choice.

2. Underlayment. The underlayment, sometimes called roofing felt, is a strong, water-resistant layer that goes directly on top of the decking and is tacked to it. On older roofs, “tarpaper” was used—felt that was treated with asphalt for waterproofing. Modern underlayment is much more durable than older felt formulations, and it’s more resistant to temperature extremes and weather. This underlayment sheds any water that makes its way through the shingles.

3. Shingles. The shingles are the layer that goes on top. Most shingles are made primarily of asphalt, with granules embedded in the upper surface to help keep the sun off the asphalt. Like any asphalt surface, the UV light of the sun can break down shingles over time and cause holes and erosion.

These three systems work together to create a cohesive, weather-resistant whole.

Shingle types

Shingles themselves have a few different types and grades of quality.

  • Three-tab. The simplest type of shingle, three-tab shingles are a single layer nailed to the decking over the underlayment. They’re the cheapest, thinnest, and least durable option, but they do provide some protection.
  • Laminated/architectural. These shingles are made up of multiple layers laminated together for more weight and durability. They’re a mid-tier option and have a longer manufacturer’s warranty than three-tab shingles.
  • Class 4 impact-resistant. This shingle subclass is a thicker, impact-resistant shingle that’s particularly helpful in areas that are prone to hail. They’re the best option for durability, and in some areas, certain insurance companies will offer a break on homeowner’s insurance if you install these shingles. Almost all of these are laminated shingles.

No matter what shingle actually ends up going on the roof, the final factor of the roof is the most important: the installation. A well-installed roof will keep your home safe for years, while a badly installed roof won’t do nearly as good a job. 

If you’re looking to get a roof replaced, reach out to us for a quote. We’ll make sure to get the job done right.

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