Ice damming — Low-slope roof — Resolvable or hopeless?
[ SUMMARY ]
I own an older home in Ontario Canada that may have been built between the 1920s to 1950s. It originally had knob & tube wiring.
Each winter I have to deal with ice damming along 2 sides of the roof, no where else. The areas in question are a Low-Slope roof (3/12 pitch, east & west side of the ridge) and a Cathedral style roof (8/12 pitch — inside the home there is a sloping ceiling that is covered by drywall). See a photo of the home: http://imgur.com/sXUzfzG.
My goal is to stop the ice damming.
[ ROOF MEASUREMENT ]
While standing on the roof, the measurements are as follows:
** See a bird’s eye photo: http://imgur.com/uTBMOK7
* Low Slope (West) – Pitch: 3/12 || Dimensions: 12′(from eave to ridge) x 34′(from North to South)
* Low Slope (East) = Pitch: 3/12 || Dimensions: 12′(from eave to ridge) x 20′(from North to South)
* Cathedral = Pitch: 8/12 || Dimensions: 10′ (from eave to ridge) x 14′ (from North to South)
[ ATTIC DETAILS]
The attic is beneath the Low Slope (East) & Low Slope (West) regions. The Cathedral, of course, has cavities which lead up into this attic opening. Access into the attic is only threw a tiny hatch on the upper floor in the home. Within the attic I’d say there’s about 36″ from the ridge to the attic floor and so one can only crawl threw it. At the moment the attic is filled with old cellulose (came with the house) and new cellulose (i had a crew add more overtop). In total it is perhaps 12″ thick but I can’t confirm if it is evenly distributed throughout the attic space.
The home has your typical Home Depot perforated 4-panel soffit vents along its exterior perimeter. However, I’m fairly confident most, if not all, soffts are obstructed by wood and/or cellulose; air intake is almost nil within the attic. There are two Maximum Ventilation (model #301) exhaust vents at the top of the roof. There is a bricked chimney running threw the attic up to the roof, along with 2 bathroom vents (non-insulated flexible hoses) and a vent stack. Though i can’t confirm i’m sure there are some open stud cavities hiding in the darkness of the attic. Lastly, the roof decking is barn-board NOT OSB or plywood.
[ PROBLEMS & SUGGESTIONS ]
I’m experiencing some serious ice damming along the Low Slope East and West regions and the Cathedral. The photo above, showcasing some ice damming, doesnt do the problem justice as it was early in the winter at the time. Within the attic you can see several black colored wood — rafters or the barn-board sheathing (i suspect moisture has been collecting up here for years).
I’ve asked several local roofing companies on how to resolve this issue. On top of opening all soffit vents and adding the generic pink baffles between every rafter, they’ve suggested some of the following:
* Dont use shingles, go with metal roofing
* Cold Roofing = a new decking overtop the existing but with an air gap in between decks
* Remove all existing attic insulation, air seal the attic floor, then blow in new insulation
* Remove the existing low slope and cathedral roof and replace it with a steeper pitch new roof
[ MY THOUGHTS ]
At the moment i’m leaning toward having the following performed:
- Remove the roof’s barn board sheathing to expose the attic
- Remove all the existing attic insulation to expose the attic floor
- Air seal all the visibly obvious problem areas (chimney, vent stack, bathroom flex hoses, open stud cavities, etc)
- Open all soffits between every rafter and add standard pink baffles between every rafter
- Blow in new cellulose onto the attic floor to a height of 18″ to 20″, no more than that leaving at least 16″ air gap from the ridge to the top of the new cellulose for cold / warm air exchange.
- With the old barn board sheathing already removed lay down new OSB sheathing for the entire decking.
- Install a ridge vent running from North to South (34′ run).
- On the new sheathing place quality ice and water shield from eave to ridge protecting the entire deck.
- Install new shingles.
WHAT ARE YOUR SUGGESTIONS TO ELIMINATE MY ICE DAMMING PROBLEM?? I’m hoping for a guaranteed solution.
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