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Why does my asphalt shingle roof look discolored?

Explaining Petroleum Discoloration In Asphalt Roofing Shingles

One of my goals as a local roofing contractor is to educate my clients and consumers by addressing common questions or concerns that come up during the re-roof process. One of the common issues I have seen in recent years with asphalt roofing shingles is what is called “petroleum discoloration.” This is where a certain number of shingles might look darker than others on a roof. This can create a very blotchy look which is unappealing and a definite concern for a home owner that just spent their hard earned money on a new roof. The question that comes up in this situation is “will my roof always look like this?.” Let me take a moment to explain this common occurrence and hopefully relieve you of your concern.

How Asphalt Shingles Are Made 

Explaining Petroleum Discoloration In Asphalt Roofing ShinglesAsphalt shingles have 3 basic layers including a fiberglass mat, a coating of asphalt and special colored granules which provide aesthetic appeal and waterproofing properties. As you likely know, the asphalt that covers the fiberglass mat is a crude oil or petroleum based product. While most major roofing manufactures have a very precise and scientific process of creating their shingles with incredible technology, petroleum viscosity can at times still create “spotting” on the shingles. Viscosity is the thickness and density of the petroleum. If the oil utilized on a particular run of shingles varies slightly in viscosity then those shingles that have the heavier oil can appear to be darker than others. This is often evident when the roof is installed and can be seen pretty easily from the ground.

What Should I Do?

The first reaction when a client sees this issue is to file a claim with the manufacturer based on “discoloration” of the shingles. While this is a common concern for home owners, there really is not that much reason to worry. Time is always the very best indicator of how temporary or permanent a problem is. It is proven that over time the oil will evaporate and the discoloration or blotchiness will fade out, and the shingles will match and have consistent coloring.

Technical Documentation To Support This Report 

GAF Roofing Corporation recently released a technical data bulletin on this top which can be found on their website. This document clearly explains the topic and shows how the oil staining will disappear.

About Us

Chase Construction Northwest, Inc. is a GAF Master Elite (steep slope) and Master (low slope) roofing contractor serving the Puget Sound. We have been installing quality roofing systems for more than 15 years. You will not find better roofing services in the area. We install asphalt shingles, metal roofing, torchdown, TPO. PVC and more. Our service areas encompasses Seattle, Tacoma, Gig Harbor and all the surrounding Puget Sound cities. Schedule a free roofing estimate today by calling us at (253) 544-3651 or filling out our free estimate form.

Explaining Petroleum Discoloration In Asphalt Roofing Shingles

1 thought on “Why does my asphalt shingle roof look discolored?”

  1. My roof is discolored but I do think it’s because the roof is in need of repair. As you said, the discoloration should fade out, but mine hasn’t. Do you think it would be a good idea to have my roof reshingled?

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