I’ve inspeced many homes in our area and many of the 70+ year old homes originally had a cedar shake roof. I always explain to our clients that the gaps in the lap boards were very important to ventilate the attic and allow the shingles to dry out.
Ususally, when there is a re-roof, I see three different methods. Some roofers will do a tear-off and leave the cedar shingles, lay down tar paper, and install the composit shingles over the top. Other times, I will see a full tear-off and 1x’s will be nailed to the rafters ro fill the gaps and then the new roof installed. Lastly, I will see a full tear-off and OSB installed over the oringinal deck and then installation of composite shingles (the best IMO).
Please take a look at the pictures attached. I would like to know if this is a defect or not. The roof is approx 3 yrs old but I think the workmanship is very poor. There was a full tear off but the roofer did not fill the spaces in the original roof deck (built around 1900). What do you think?