We had our roof completely redone approximately 10 years ago. We just found out that our shingles, which were CertainTeed Horizon have cracks in all of them. These were 25 year shingles and we purchased them because we wanted the best shingle on the market. These were highly recommended to us at the time. We have since found out that these shingles were defective. Now we are faced with having our roof redone. My questions is what shingle out there is a GOOD shingle? We want to use a dimensional or architectural shingle. We have been told by several contractors that we can shingle over our existing one layer and others said that we should do a complete tear-off. We need help and advise. Thanks!