Bought my first house in 1979. It was a lakefront cottage in Lewisboro, NY. - sub- maybe even exurban NYC. While installing a wood-burning flue through, the roof, I counted seven… yes seven layers of asphalt shingles! I can’t imagine the weight!
And the structure itself had 2x4s as rafters, 24” on center. Scared the hell out of me. But the rafters were solid black walnut. House built in about 1918. No official records, just some old photos 1915-ish no house, and 1920-ish there’s the house.
The next winter we had a large slushy snowstorm, 18” of snow heavy as lead. I paced back and forth knowing something was wrong, but what was it?
Finally it dawned on me…. The normal creaks and groans from the house in normal times were completely gone! I concluded that the weight of about 18” of slush stuff on the roof had compressed everything up there down so that there was no room left for squeaks and groans to propagate.
So I had some dinner, poured myself three fingers of Scotch, and went to bed.
OP didn’t mention how many layers of shingles were already up there. Maybe local codes would permit one more?
Soon thereafter I married, had a little girl, and as soon as she took her first step, the house magically shrunk and we moved to a more kid friendly house in a more kid friendly neighborhood. It was surely fun while it lasted.
Last I heard, the house was still standing.
-Skip