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  • #46
    Once again I am late in responding (I binge read this forum and PM so I am frequently a couple of weeks behind on either forum).

    My first house, now rental and site of my workshop garage, suffered occasionally from an ice dam located over the kitchen. This house is unique in that it is a log house with 7 ft high exterior walls, originally no ceilings except for bath and kitchen. In the early '60s the 2nd owner had ceilings installed at 8 ft high, running into the sloped ceiling/log rafters along the perimeter walls along with installing minimal insulation, as was common back then, but there was no ability to add soffit vents. When I bought the house in '85 I added cellulose insulation over the existing thin batts. My first reroof on this house was in '94, with no change in attic ventilation.

    Before reroofing this house again, I did a lot of research on how to properly be able to vent a roof, especially with the limitations of this house's construction. I reroofed this house in '18 and replace the few can vents with shingle over eave vents and ridge vents. To be able to get functional eave ventilation, I removed the decking from the perimeter wall to about 3 ft upslope, I added pour in insulation as needed and then installed insulation baffels before reinstalling the (old growth redwood) tongue and groove decking. Images attached - I don't have an image of just the shingle over eave vent installed. The image of the installed eave vent already has the ice shield installed over it. Final image of the house roof, taken from the roof of my workshop garage, shows the eave vent on the roof section on the left. The eave vent projects up about 1 inch - same step up as a ridge vent. Oh, and where I had the ice dam over the kitchen - there was a cavity with no insulation above a upper cabinet soffit - I would never have found the lack insulation without removing the decking. This house has 24 inch soffits/overhangs so the shingle over eave vent is about 30 inches in/upslope from the faceboard.

    BTW, there is a world of difference in ice and water shield brands. Most brands just meet the ASTM standard. And then there is Grace brand ice shield. Many roofers dislike working with Grace. It costs about double and it is much more pliable and gummy when warm/hot. Where it touches the roof is frequently where it will stay, whether that is where you intended to install it or not. The Grace flows around nail shanks. Typical failure (water leakage past a properly installed ice and water shield) is when the nail head rusts off and water wicks past the ice shield - that is typically not the case with Grace until the shank rusts away. I have reroofed half a dozen houses in the past 27 years (since I was first required to use ice shield) and this was the first on where I used Grace - usually I just bought the cheap house brand ice shield . On this house there is a vaulted ceiling over the living room where I was unable to vent many of the cavities between rafters due to a wide chimney, large skylight and a valley. Here I ran the ice shield up much higher than required with an 18 inch overlap (doubled - Grace allows this for "difficult" roofs) and used stainless steel roofing nails. A bit more pricey in material cost, I did the labor, but I am counting on this new roof lasting beyond my lifetime. And if you want to accuse me of being a Grace fanboy - so be it.

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    Last edited by aribert; 03-12-2021, 02:37 PM.
    Metro Detroit


    • #47
      I don't remember the brand of ice & water that the roofers used. But that wasn't the reason for the backup and leaking.
      Before they came out with ice & water they used starter strip which was basically a roll of shingle material. They would stick the first 12" or so of it down with mastic along the drip edge. At the time that was state of the art.