This roof was originally a 3 tab shingle with two layers on parts of it. In this project we had to redeck parts of the roof. We changed out the exhaust vents and put in new ridge vents. The chimney didn't have a cricket, which is used to divert water away from the base of the chimney. When we replaced the roof we installed a new cricket as well. The new shingle installed was a Certainteed landmark.