How high winds damage roofs.
This blog is taken from a letter to an insurance company defending a client who had severe roof damage from a tornado, with ongoing subsequent leaks. The insurance company took the position that the wind damage was "wear and tear," that the leaking was "coincidental to and not because of the tornado," and denied her claim. This homeowner contacted her home inspector!
Any roof can leak at any time depending on the direction and force of rain. That is an axiom that you can take to the bank.
In April 2017 we experienced a tornado that caused severe damage to our roof shingles.
This is a photo of one aspect of my roof. You can see a section of shingles on the lower left and lower right which were removed. Other shingles were shredded.
Leaking happened immediately from two skylights and at the lower right in this photo where the roof meets the corner of the siding. These thermal images above are from inside my house just under that siding corner.
The leaking continued until the roof was replaced. A black and white image is the best way to demonstrate leaking, but clients (and insurance companies) want sexier images, so a color palette was chosen to best describe the leaking locations.
When wind hits a roof its effect is not uniform over the entirety of the surface. Some spots will experience higher and other spots lower wind pressures. For that reason damage can be more or less severe.
The direction and force of rain can change during the course of a tornado, which usually doesn't affect a house for a very long period of time.
Windward and leeward, some areas of the roof can experience positive pressures at the same time that others are experiencing negative pressures. The photo above is on the windward side of the tornado's approach - meaning the direction from which the wind was blowing.
Positive pressures lift shingles through pushing; negative pressures lift shingles through suction.
That is why on the windward side photo above the shingles are both shredded through pushing and removed through suction. The same kind of damage happened on the leeward side of my house.
Leaks happen because of material movement. Where shingles move even a little the wind will get under it and drive water to those spots. And leaking can happen even where tar paper is still present.
Damage starts as a small spot, and then with continued rains the damage worsens and leaks become more and more pronounced. Leaking is not "coincidental" to a tornado, or wind damage. It is "incidental." Coincidental means there is no causal relationship, things just happen. Incidental is best defined as something that happens as a consequence of something else. On both my roof, and my client's roof, the damage and leaking were incidental. So when an insurance company takes the position that leaking after a tornado is "coincidental," that position cannot hold up to the science of tornadic roof damage and leaking.
My recommendation: a roof is a fickle place. It can and will react to all kinds of weather. Newer shingles, the architectural shingles that look like a textured layer of roofing, are designed to handle winds as high as 140 mph. They are thicker and more solid, and have better glues to stick them together. Some newer shingles are called "forever shingles." While they aren't really able to last forever, they will probably last a long time, even 30 - 35 years.
Note: following my letter to the insurance company my client's roof claim was approved. She was elated and her home inspector gets a Gold Star. Aw, shucks.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560