Live in a 1920 built home in Watertown, NY. No sheathing on roof–just 1x boards with paper and shingles–three layers as of last count and job done by previous owner. Attic is not vented in any way. Insulation is okay but could be a better. Multiple feet of snow on roof now from big lake effect snowfall we’ve gotten recently. Many leaks have appeared in interior of house along perimeter walls and ceilings, to include window trim.
Is this leakage a result of ice damming? And even if so, would a perfectly built roof leak as well? Is there any sure way to put on a new roof and not ever worry about ice damming, short of installing a heating cable?
If, and more likely when, I put on a new roof, I would intend to install a proper layer of plywood sheathing. I would think that leaving the original 1x boards on the rafters is okay (unless wet or rotten). What thickness of plywood is the best for a steeper pitch roof and the likelyhood of a great deal of weight in the winter months? (I am leaning towards 5/8", but I do not know if this is needless overkill)
What would the best type of venting be on this home, given that the volume of snow in the winter can possibly block a ridge vent?