Prevent Ice Dams from Forming on Your Roof

When temperatures plummet and snow

starts falling, many of us reach for the shovel

or snow blower. Smart homeowners,

though, remember to look up too — and

check their roofs for ice. Ice dams are accumulations

of ice on the edge of the roof —

and they mean Big Trouble for you and

your home, so be on the lookout.

What’s the big deal, you ask? Ice dams

result in water seepage, which can rot roofs,

destroy insulation, flood attics and ruin

gutters. Moisture damage can extend far

inside the home, damaging ceilings, paintwork

and belongings. The dampness encourages

mold, too, which can trigger nasty

allergies.

You may have heard that gutters cause

ice dams by providing a place for water to

collect. Wrong! You may also have heard

that installing heating cables along the gutter

line is the best way to prevent ice dams.

Wrong again! Yep, there’s a lot of misinformation

out there. Let’s look at where ice

dams really come from.

How Ice Dams are Born

In poorly insulated homes, warm air escapes

through the ceiling and into the attic.

If ventilation inside the attic is also inadequate,

all that warm air has nowhere to go.

Result: the roof’s temperature starts to

creep up higher than the outdoors air temperature,

causing accumulated snow on the

roof to begin melting.

Water then trickles down the slope of the

roof until it once again hits a cold patch,

usually the gutter. There it refreezes, gradually

forming a dam that prevents runoff.

Additional melting snow, having nowhere

to go, starts seeping inside the house — and

that’s where the homeowner’s headaches

begin.

A Cool Solution: Insulation and

Ventilation

The only way to permanently eradicate

ice dams is not to warm your roof up (with

heating cables) but to cool it down with

better insulation and attic ventilation. Until

then, you’ll go right on experiencing ice

dams in severe weather. Any other strategy

will provide a temporary fix, at best.

In northern states, attic insulation

should be at least 12 inches deep. Make

sure it is installed correctly, without any

gaps between sections, and in conjunction

with a vapor barrier. While you’re at it,

check that attic heating ducts are located as

far as possible from the roof.

Also check around light fixtures, chimneys,

bathroom fans and anywhere else

heat might escape upwards. If you discover

small holes, seal them up with caulk, spray

foam or weather-stripping.

Next, evaluate your attic’s ventilation

system. Are there adequate inlet and outlet

vents? If not, look into installing a continuous

soffit and ridge ventilation system.

Here’s how it works: a vent is installed that

runs the entire length of the roof at its apex.

We all know hot air rises, right? In this

case, the hot air now has somewhere to go,

naturally flowing up and out through this

new attic vent.

Meanwhile, that draught of air upwards

and outwards creates a vacuum, sucking

cold outdoors air into the attic via soffit

vents, further cooling down your trouble

zone. The beauty part is there are no fans or

wires or anything else to be maintained.

Nature does all the work for you!

Help! There’s An Ice Dam on My

Roof. Now What?

Your best strategy is to sit tight and wait

for the ice to melt away. Later you should

focus on preventing future dams by making

the improvements described above.

Before you decide to manually chip away

at an ice dam, know that it’s not recommended,

and best left to a professional. For

one thing, you could seriously injure your-

self. (Never, ever climb up on an icy roof. If

you must inspect the ice dam up close, use

a ladder and beware of falling debris.) Second,

forcibly dislodging chunks of ice could

easily damage your roof and gutters, worsening

your leakage problem.

If you really, really can’t stand just waiting

it out, here’s an ice-melting tip courtesy of

This Old House: Cut the legs off a pair of

pantyhose, fill with calcium chloride ice

melt and lie them down the slope of the

roof so that each leg crosses a section of ice

and the toes dangle over the edge of the

gutter. This should melt small channels in

the ice, allowing runoff to occur.