Wood Roofing: Cosmetic vs. Performance Damage

Wood shingles and shakes comprise a small, but significant, portion of the steep-sloped roofing market. These wood roofing products seem to show up in more and more hail claims. What is performance-reducing damage and what is simply cosmetic damage?

Properties of Wood Roofing

In general, wood roofing is very fragile as it ages due to normal seasonal weather and exposure to ultraviolet (UV) radiation. Some types of wood roofing materials are more fragile than others. Longevity and physical properties of wood roofs vary between species of wood and even within a species depending on the age of the lumber when it was harvested. Foot fall splits and broken ridge shingles are very common deficiencies found on wood roofing. It can be very difficult to differentiate between hail impact damage and foot fall splits.

Categories of wood roofing damage:

1. Cosmetic damage comes in the form of dents in lighter gauge metal and spatter marks on the roof shingles/shakes. Although these two conditions would not be considered performance-reducing damage, the observation of this “collateral damage” indicates the roof has experienced a hail event which could have damaged the roof. This typically does not call for the replacement of the items unless the damage is to the extent that it becomes performance reducing.
2. Performance-reducing damage comes in the form of a hail strike which is directly over a fresh split or adjacent to a fresh split where the hail struck an unsupported section of the shingle/shakes. If the shake is new and still retains much of its original thickness, it would typically take hail over 2-inches in size to cause a split. Badly weathered shakes can split and crack with 0.75-inch hail. This situation may call for the replacement of the roof cover.

Inspection/Evaluation Tips

Before determining the extent of the storm damage, observe the condition of the roof beyond any storm damage including quality of shingle, age, installation defects, etc. Wood roofs drain in a different way than do asphalt shingle roofs. While rain on an asphalt shingle roof flows off as a sheet of water, on a wood roof (particularly shakes) the water finds the path of least resistance causing some of the shakes to be exposed to more water than others. This causes premature erosion to a wood product in certain areas which can sometimes give the appearance of hail damage. Although this natural weathering is not related to a single storm event, it can make a roof more susceptible to damage by hail or wind, and could cause damage which can be misinterpreted as storm damage. Examples of this are presented below.

Identifying Damage Types:

Spatter/Splatter marks – Spatter marks are areas where the natural oxidation and dirt, which have accumulated over time, is removed by the cleaning effect of the hail impact. Spatter marks are seen by owners on fences and other surfaces which are subject to oxidation. These spatter mark observations typically make owners believe their roof was damaged during the hail event. Spatter marks are cosmetic in nature and are not performance-reducing damage. Splatter marks typically do not require roof replacement. They usually disappear in one to two years. They do not affect the water shedding ability of the roof, nor do they affect its remaining service life.

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Spatter marks on wood fencing-cosmetic damage | Spatter marks on wood roofing-cosmetic damage

Splits:

Spatter marks on wood roofing-cosmetic damage.

Foot fall splits can be very difficult to differentiate from hail impact splits. “Foot fall splits” are splits in the shingle or shakes that are caused by people walking on the roof. This could be the owner, contractor, or an insurance adjuster. As part of the evaluation, one must rule out splitting, which occurred naturally during the aging of the shingle/shakes. Natural splitting will be apparent by the aged look of the wood within the split. Fresh splits are recently caused and can be determined by the lack of weathering within the split and the ability to push the split together so the split seems to disappear. Following the determination of which splits are fresh, the splits which have a direct impact mark on the split line are considered performance-reducing damage caused by hail. See photos below:

Note: Impact mark directly over split. Split appears fresh with unweathered wood within the split

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Some of the shakes may have a fresh split but no impact is observable on the split. There may be an impact mark which occurred over an unsupported area of the shingle causing the shingle to flex and then split. Check each shingle carefully. The reason these splits are considered performance-reducing damage is because the shingle may have a portion of itself that is no longer secured by nails therefore it could come loose and expose the underlying layers of the roof. Other clues to foot fall splits, such as footprints or other mechanical damage are also sometimes visible

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Impact on unsupported shake caused fresh split. This is performance damage.

Puncture:

A puncture is a hailstone impact that punctures through a shake or shingle. This takes a very large hailstone on a deteriorated roof surface. The puncture exposes the underlying layers, sometimes puncturing through several layers, reducing the remaining service life of the roof, therefore could require replacement of the roof cover.  Erosion can easily be mistaken for punctures.

This article was originally published by Property Loss Research Bureau (PLRB). Reproduced by permission from PLRB.