Asphalt shingles diagonal cracks
Asphalt shingles diagonal cracks
(OP)
I saw an unusual problem and I'm wondering if anyone else has. On hail damaged asphalt shingle roof, diagonal cracks at 3 foot spacings can be seen in the shingles. See attached photo. When on the roof, there are more cracks than can be seen in the photo. The cracks aren't due to hail damage, so what cause them. To me the logical cause is due to torsional loads (wind)on the building, but why did the shingles crack and not the sheetrock ceiling? There are cracks in all 4 roof sides, and they change directions indicting a circular pattern. One interesting point is on one roof side the cracks run one direction at one end and the opposite direction at the other. It's possible the ceiling could have been fixed. I'm questioning if the cracks are the result of a manufacturing defect or cheap shingles? It's a smaller wood framed building, 50' x 61' x 9', with slab-on-grade construction built in the early 1990's. The roof is a hipped roof with a 5:12 slope, pre-manufactured trusses @ 24" c-c w/ 2x6 top & bottom chords and 4' overhang. It has 5/8" cdx roof sheathing. Over all the building looks petty solid, but fastener type and spacing for wall or roof sheathing is unknown. This isn't a complex building or an expensive problem, but I haven't seen it before and I find it interesting and thought other engineers might also. Thanks,






RE: Asphalt shingles diagonal cracks
I have installed many 'a roof myself over the years.
It appears that the cracks are on the third tab of a three-tab shingle.
I think this is directly related to the installation technique.
Although it is not recommended by most manufactures, some roofers will lay the shingles straight up the roof in 3 foot wide passes rather than "pyramiding" the shingles.
This causes the roofer to lift up the last shingle on the end as he makes his way up the roof with each successive coursein order to slip the next shingle underneath.
RE: Asphalt shingles diagonal cracks
RE: Asphalt shingles diagonal cracks
I generally agree that it is most likely an installer caused problem. But, they do not all appear to be on the right or third tab. Could these corners be flexing over a high nail head below?
RE: Asphalt shingles diagonal cracks
If it was built in the early 1990's, it is about time for a re-roof. The striations in the shingle indicate a loss of granules on the areas that were likely bent up during installation as TJ noted.
RE: Asphalt shingles diagonal cracks
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Asphalt shingles diagonal cracks
RE: Asphalt shingles diagonal cracks
Also, while unsightly, these cracks will not cause a leak because of their location.
That roof has already seen the better part of its life. Most shingles of that time were 20 yr warranty and the high end 25 years.
Ron can probably verify the previous statement.
Ron also may have more input, but I have been called to some "hail damaged" shingle roofs (sister is an insurance agent). They were all after local storms widely covered by local media. It amazed me that nearly every single one of these "hail damaged" roofs was already 10 yrs past the time when it should have been replaced, in a terrible neighborhood, and owned by a customer a few months behind on their insurance premium.....I'm just saying
RE: Asphalt shingles diagonal cracks
Agree also that his has nothing to do with the structure, structural movement or wind loading.
RE: Asphalt shingles diagonal cracks