Ice Dams and Toledo Roofs
Every winter the same conversation happens: someone buys heat cable for the eave. It treats the symptom of a problem that starts in the attic.
The sequence
Extending ice and water shield further up the slope during a Toledo reroof costs $250-800, which is small against a $9,500-16,500 roof.
- Warm air escapes from the living space into the attic - through the attic hatch, recessed lights, plumbing penetrations and gaps in the top plate.
- It warms the underside of the roof deck.
- The bottom of the snowpack melts even in freezing weather.
- Meltwater runs down to the eave, which overhangs unheated space and stays cold.
- It refreezes there, building a ridge of ice.
- Later meltwater pools behind that ridge, finds the shingle laps, and goes under them.
Notice what is missing from that sequence: the roof covering. Shingles are designed to shed water running downhill, not to hold back a pond. A perfectly good roof will leak under an ice dam, which is why 'we just had a new roof' is no protection at all if the attic was never addressed.
What each fix actually does
| Fix | Typical cost | What it does |
|---|---|---|
| Air sealing the attic floor | $600-2,500 | Removes the heat that starts the whole thing |
| Adding insulation to depth | $1,200-3,500 | Keeps the deck cold |
| Correcting soffit intake and ridge vent | $600-1,800 | Flushes residual heat out |
| Ice and water shield further up the slope | $250-800 at reroof | Does not stop the dam, stops the leak |
| Heat cable at the eave | $300-900 | Melts a channel. Treats the symptom, uses power every winter |
The first three items address the cause; the fourth limits the damage; the fifth manages the symptom. Most homeowners buy the fifth first because it is the cheapest and the most visible.
If you are reroofing anyway, extending the ice barrier further up the slope than the code minimum costs a few hundred dollars and is the single easiest thing to add to the scope.
The ventilation trap
Ridge vent is exhaust. Air leaving at the ridge has to be replaced by air entering at the soffit. If the soffit intake is blocked - and blown-in insulation pushed into the eaves is the usual culprit - the ridge vent instead pulls conditioned air out of the house, which makes the attic warmer and the ice dam worse.
Baffles fitted at the eaves keep an air channel open above the insulation. They cost very little and they are the difference between a ventilation system that works and one that is decorative. Ask any roofer whether they are installing them.
Common questions
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Get the roof and attic looked at together
Tell us whether you have had ice at the eaves or staining on a top-floor ceiling. A contractor who looks at both will give you a more useful answer than one who only quotes shingles. No charge, no obligation.
Or call (419) 567-8805