What's on the roof now is tarpaper over 1x12 wood roof boards. Can I install the cedar shingle directly over 1x12 boards? I would remove the tarpaper, nail the shingles directly to the board with 7" exposure, and afterwards cover the shingles with Thompson's wood sealer.
I have build a shed roof like this 5 years ago and the shingles seem to be holding out fine, so I'm not sure if it is absolutely necessary to have the air space under the roof shingle. The shingles are expensive and I would not want them to fail after 5 years. Thanks,