I'm trying to troubleshoot a 2 year old t-lock roof on a 3/12 leaking in the field. Had a couple of roofers out and one guy thought it was the old 1x12 sheathing with shrinkage gaps that allowed some of the nails to puncture the shingle. That and the 3/12 not shedding water as well as a steeper pitch is causing about 4 or 5 leaks in the field. The leaks seem to be in a straight horizontal line. The closest valley or chimney etc. is about 3 houses away. I thought this roofer probably had the best explaination and we'll probably let him put the new laminate roof on but wanted to check for input from you guys first. Also we were thinking of leaving the old roof on to help bridge the gaps and save some money. RT