A:It is possible, and this is assuming you are using the term 'professional' in the most liberal sense, that the shingles were stretched vertically as they were laid from the eave edge to the peak of the slope. This would be done to cut down on the amount of material used and should have been used for a proper application. I have run into this situation with both 3-tab and architectural shingles. This will compromise the integrity of the roof and may lead to premature leaks.
