Damaged Composition Roof Shingles
This is a good example of damaged composition roof
shingles, where someone installed them over a wood shingle roof, without
using any roofing paper. The roofing paper should have been installed
over the wood shingles and then the composition shingles would be
installed over the roofing paper.
This is another example of you get what you pay for. I doubt if a professional roofer, who was licensed in your area, would have ever done something like this.
There is a good chance that this roof doesn't leak. However, there could be mold or fungus growing on top of the wood shingles and even inside the attic. Usually extreme temperatures, will cause a roof like this to deteriorate sooner than normal.
If you live in an area where snow accumulates on your roof, the moisture could actually be seeping through the first layer of composition roofing and absorbing into the wood shingles. Once this starts to happen, and the wood shingles can't dry out properly. Your roof could soon start to suffer from mold, fungus and dry rot.