New roof-Shingles buckling

This roof was installed last October on OSB sheeting (it was an original cedar shake roof).

I’ve not seen this issue before; any thoughts on whats happening here?Windsor roof

OSB as a sheathing for a roof is bad stuff. When it gets wet/moist it will expand more than a typical plywood. If the roofer did not leave enough spacing between the sheets, you may get buckling at the seams. Were you able to look at those areas from the attic?

No the access into the attic was not possible, due to the confined space.

Why was it confined? anyway… it’s due to the sheathing expanding and buckling at the seams due to improper OSB spacing/nailing schedule and or fastener type, but attic access is needed to inspect the installation of the sheathing and to see if the roof is leaking, wetting the OSB. Also, I see no gutters.

Internal gutter system, EDPM lined.

That’s rare roof gopher trails. unlicensed, contractor gopher labor doing a side deal
“cause i work for a real roofer”.


Those look like issues with the underlayment. Some of the wrinkles are obviously wrinkles in the underlayment. The long horizontal lines (longer than a sheathing panel), in my experience, are typically caused by installing a row of underlayment, then shingling up to the top of it and installing the next strip of underlayment and repeating. This leaves the lower edge of the underlayment sandwiched between two courses of shingle, which prevents the entire row of shingles from bonding. No manufacturer that I am aware of supports this installation practice.

I always either walked or tried to reach the first seam from the eave to lift the tabs and verify that the underlayment was between the shingles. There were multiple new roof installations that were entirely torn off and reinstalled as a result of my reporting this.

Here’s how I used to document the installation issue. Anyone feel free to use or adapt as suits you, but I urge you to verify before making such a definitive statement.

Noted improper installation of felt underlayment at several locations (possibly more) of the roof. The installation does not comply with any manufacturer’s installation standards. Felt underlayment should be laid over the roof surface and shingles installed over top of it. In the areas observed, the underlayment has been interleaved with the shingles (i.e., the lower edge of the felt lays between two consecutive courses of shingles and separates them). This condition often appears as one or more clearly defined horizontal lines in the roof surface. Shingles are designed so that each consecutive course bonds to the one below it. This is essential for resistance to wind lift and damage during high winds. When the felt underlayment is between courses of shingles, they cannot bond to one another as intended. The only proper repair for this defect requires removal and replacement of the roof covering. This is a builder / installer defect and is not covered by the manufacturer’s warranty.

For the run-of-the mill wrinkles in the underlayment I would use a variant of the following (again, feel free to use or adapt)

Ridges observed on multiple locations on multiple areas of the roof surface. This is an indication that the roof sheathing or underlayment is not properly installed. Buckling can negatively affect shingle life and is not covered under shingle manufacturers warranties. Shingles that are do not lie flat cannot properly bond to the shingles below, making them vulnerable to wind lift. Needs repair to ensure that all shingles are properly bonded. (Ref: IRC Section R905.2.7 Underlayment application). … Distortions in the underlayment shall not interfere with the ability of the shingles to seal…


Excess moisture in the underlying wood sheathing and felt paper can lead to buckling. A comprehensive inspection by a qualified roofing contractor is called for.

Not that it really matters, but was there a permit pulled for the re-roof? If not, you could assume an unlicensed contractor did the work…at the least, inexperienced. Those horizontal ridges appear to be uniform in spacing - I’d be inclined to agree with Mr. Evans’ assessment. I’ve never seen this before, but that makes sense. Regardless, it needs more evaluation to determine if it’s leaking, and a lot of work to repair…Of course, any issues like improper installation will detract from the useful life of the shingle, and would have an adverse effect on the value of the home for a buyer, so it should be correctly reported.

Here is a guide from the Asphalt Roofing Manufacturers Association I’ve sent to clients after new construction shingles buckled after my inspection.

I’ve always attributed it to wet decking during installation. Not something observable during inspection. I would pursue the installers.

Hard to tell from one photo but if the buckling followed the pattern of joints in the roof sheathing, it can be caused by installing shingles over sheathing before it has had time to reach moisture equilibrium with the homesite environment.
If shingles are installed over OSB with 6% moisture content (or 4% for plywood) in a humid environment and space is left between the panels, panels will swell as they absorb moisture from the air. Shingles will buckle above joints. Like this:

Buckled shingles 1

34_Sheathing-buckled_shingles_2 copy

If it doesn’t follow that pattern, then Chuck is probably right about it being underlayment related.

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I have observed this type of buckling where the carport supports of the house has been subjected to settling and upheaval- and also where the carport supports have rotted and were subsequently replaced.