Ice damming

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?

More than likely that is from ice damning. A home without any ventilation will have this problem on a large scale. With all the snow that you are having up there i could not see what else it could be.

Normally the home has ice and water shield installed with a new roof and that can give relief to that problem but not eliminate it. Proper ventilation and insulation will only remove lets say 90% of it. There always will be some form of ice on a roof from the freeze and thaw and that is natural. A heat tape style of solution will only make the ice go farther up the roof and cause the same problems but just in a different place.

WIth three layers up there you will have to tear the existing roof off and start from scrach and that will be a good thing when that snow gets off your roof. If i had some pictures so i know what style and type of home you have along with legnth and width dimensions i can give you a detailed explaination of what you can do to ventilate the roof. Since you said you are basically not a fan of ridge vents and on those types of homes i never suggest this unless there are soffit vents already in the home. If you would like you can email me your phone number and i can call and help you understand some things and also help you make an educated decision on what your next steps are. There is a link for my email address just below the post of mine. If you are having problems with emailing me just leave your email address here and i will contact you that way. Hope i could help and have a great day.

i would leave the 1x wood on the roof and go over it with 1/2" the 1x should give you the support you need and the plywood is basically only there to give a nice smooth substrate. we would need pics of the outside of your house and probably the inside of your attic to give ventilation advice. based on your extreme climate (im between rochester & syracuse so i am very familiar with your weather) i would probably go with extra ice & water barrier. code calls for ice & water barrier to go 24 inches inside of a warm wall but i would go 60 inches because you probably have a very large ice build up due to your consistant sub zero temps.

ditto marshall