After a second huge ice storm since I moved here (Iowa), I again have
water coming in the house, due to a giant ice dam that has formed in
one of the valleys of my roof.
I had Servpro come out to chip away the ice and handle the water
damage. They told me they thought the water/ice was flowing off the
upper roof onto the lower roof and freezing in the valley. They
suggested I get gutters on my upper roof to fix the problem in the
future, but looking at the gutters on my lower roof, I can't imagine
they would help much.. They are completely frozen over. They did say
that we have had two of the biggest ice storms in 7 years and that it
shouldn't happen all the time. The problem was that there was so much
ice, it built up higher than the moisture barrier that runs up the
side of the house from under the shingles.
Does anyone have any advice on how I can prevent this problem in the
Agree that lack of insulation/ventilation is your core problem. The
bandaid approach is to install heat cables. The only way a gutter
will work in this situation is if it has heat cables in it. Cables
are a PITA since they don't last forever and potentially present a
fire hazard, but they will work. Trouble is, it might be too late
this winter to get them installed.
Ice dams may "usually" be caused by poorly insulated attic etc. but the
storm lagman is talking about is producing "unusual" ice dams.
I've been in the same ice storms as lagman. The liquid water is coming
primarily from the sky (freezing rain) NOT from snow melt on the roof
due to "poorly insulated [or ventilated] attic". The gutters are clogged
NOT because of poor pitch but because they were filled with sleet by a
previous storm and, due to temps, were never allowed to melt so there
are blockages in sections.
lagman, you mentioned your ice dam was at a roof valley and the build up
was higher than the moisture barrier (ice and water shield) extended.
The ice and water shield should go all the way up the valley, centered,
so it's 1 1/2 feet on either side of the valley and, on the eaves, at
least 2 feet uproof from where the wall intersects with the roof.
One thing you might check is that the gutters are tilted so that, when
they are filled up, they dump runoff away from the house -- that would
be the "roll" of the gutters as opposed to the "pitch". So, in
situations like we've had in the last 2 weeks, when the gutters are
clogged, the freezing rain is dumped away from the house and is not
trapped between the gutter and roof edge to form a dam. That way, you
may get water closer to your foundation than you'd want (do you have
drain tiles and a sump pump?) but you're less likely to get an ice dam.
Thanks for the reply. I will try tilting the gutters as you
suggested, but just for piece of mind, I'd like to have some type of
melting mechanism in place in the valley. I have heard mixed results
from using heat tape. One person suggested using something called
"Ice Viper". Its basically a long bag filled with melting agent that
you put on your roof (it claims to contain chemicals that will not
harm your roof or siding).
In either case, what is the best configuration to use? Should I lay
the Ice Viper/heat tape straight down the valley line? You said the
moisture barrier will run centered along the valley with 1 1/2 ft on
each side.. So maybe I should put them a foot or so on each side of
Is the 1 1/2 ft on each side of the valley and 2 feet extended up the
wall pretty much standard for a house built in '93? It would make
sense.. The ice dam spanned about 3-4 feet across when the water was
I had a similar problem in my previous home, also with a valley. It happened
rarely. I got on a ladder and tossed large amounts of rock salt onto the
area twice a day for a few days until it all melted. Unless the same strange
weather pattern reoccurred, the damming would be gone for the rest of the
winter. And, the salt didn't hurt the roof. Might've been calcium chloride.
Dan, I'm not sure that "Ice Viper" offers any more advantage in dealing
with an existing ice dam than the homemade "calcium chloride in panty
hose". For a description of that see:
Here's what it says:
"If you live in a cold, snowy region, you already know about the
damaging effects of ice dams. The gutters clog up with ice, then water
runoff from the roof gets trapped by the dam and eventually backs up the
roof, travels under the shingles, and leaks into the house.
"While a permanent fix for ice dams usually requires increasing the
insulation, sealing, and ventilation in the attic, there is a simple way
to diminish the damage after the dam has formed.
"Fill the leg of discarded pair of panty hose with a calcium chloride
ice melter. Lay the hose onto the roof so it crosses the ice dam and
overhangs the gutter. If necessary, use a long-handled garden rake or
hoe to push it into position.
"The calcium chloride will eventually melt through the snow and ice and
create a channel for water to flow down into the gutters or off the
Note that you should put the filled hose leg "so it crosses the ice
dam", i.e. perpendicular to the dam so you create a channel for the
liquid water to run off the roof.
As far as where you want to put the melting agent (chemicals or heat):
Remember, you do NOT want to create MORE liquid water above the
potential ice dam; you want to either 1) inhibit such liquid from
forming (for example, more attic insulation and ventilation to inhibit
roof snow melt) or 2) as in your present case, if you are unable to
prevent the liquid water (rain), give it a path to quickly run off your
So, with an EXISTING ice dam, I'd be VERY skeptical about putting
something like the "Ice Viper" above the dam -- you don't need MORE
liquid water running down the valley.
As a PREVENTIVE, either the heat tape (I have ZERO experience with heat
tape/cable) or the pantyhose/"Ice Viper" down the length of the roof
valley, I don't know but I'd want to do a LOT more research on both
safety (for example, risk fire and/or damage to roofing materials)and
effectiveness before I'd do that.
By the way, as far as "tilting the gutters" goes: I didn't mean to imply
that you can make the necessary adjustment (if it's needed) now with all
the snow and ice filling them. If you find that they do need to be
tilted so that any overflow goes away from the house, I'd call a gutter
installation/repair company to find out when they could be corrected
Best of luck, Dan. Believe me, I feel your discomfort. :)
I finally broke down and had a roofer come out and give me an
estimate. I asked him to evaluate the problem I have already had and
tell me if there is anything I can do to the roof.
He said he could pull some shingles off and put a good moisture
barrier up there, then where the roof meets the edge of the house,
extend the water barrier up the side of the house. He said he could
do both for $800 to $1000., or just the moisture barrier under the
shingles for $400-$500. He of course suggested I do both He will not
offer me a guarantee the roof won't leak again higher up, but claims
this is something that should be done given the design of my roof.
Does this sound reasonable, or are they just trying to take advantage
of someone who is desparately looking for a solution?
What he's suggesting certainly wouldn't hurt. But, what about insulation and
ventilation? Is there enough insulation in the attic to keep it nice & cold?
What about vents in the eaves? The idea is to keep the snow from turning
into ice. Keep it fluffy.
Hi, Dan. I'm not sure what you mean by "where the roof meets the edge of
the house, EXTEND THE WATER BARRIER UP THE SIDE OF THE HOUSE". Are you
talking about under flashing? I assume you're talking about using
something like Grace Ice & Water Shield or Certainteed WinterGuard;
those products are UNDERlayments and not supposed to be exposed for any
length of time to sunlight -- they are applied to roof decking under
shingles or under flashing or behind gutters or behind drip edge, etc..
Additionally, they require DRY decking (or whatever substrate) and
TEMPERATURES well above freezing (at least 40 degrees F) when they are
applied. Read about WinterGuard at:
Here's info on the Grace Ice & Water Shield:
Is the roofer planning to do the work now with winter temps and
conditions? If so, how? Did he talk about the likely need to replace
some of the decking; if so, how much and how -- particularly since your
problem involves valleys?
As far as the cost, as a mere homeowner (not a roofer), depending on HOW
the roofer intends to do the job, it doesn't seem outrageous. In fact,
depending on how the work SHOULD be done, it seems to me that it may be
low; so I'd want to be sure that what the roofer intends to do is "good
practice" and likely to be effective.
Dan, I'm afraid I don't have the expertise to properly answer your
question but I can suggest where you might find some experienced roofers
who may be willing to suggest possible options -- but don't expect them
to be very "precise" as far as what roofers should charge -- highly
variable due to location, weather, etc. I recommend you register and
post your question(s) at Roofing/Construction Questions forum at:
Best of luck, Dan.
When I say "Where the roof meets the house", There is a room on our
second floor that "juts" out from the roof. Here is a (small) picture
of our house:
The problem area is where the garage roof meets the side of the house
(there is about a 45 degree angle between the garage roof and the
house, this is where the ice dam formed and where the water leaked
As I understand it, here is what he plans to do:
-Take off original shingles all along the valley.
-Put Winterguard all down the valley. He said the stuff is 3 feet
-I remember him mentioning something about step flashing. I think he
wants to add some down the slope of the roof where the roof meets the
- He mentioned using some sort of roofer's tape to tape off the top of
the flashing so ice can't get in back of it.
- I think he said something about adding a special piece of siding
- Match the shingles and replace.
He didn't say anything about replacing any of the decking, just making
what is up there water tight.
Those were the main things, and I have a written estimate. He did say
he would be able to do it in January unless we keep getting snow.
Dan - What you say the roofer is proposing sounds reasonable to me --
but, as I said, I'm a homeowner (with 2 valleys on a more simple roof
than yours), not a roofer. Again, I encourage you to post a description
of your problem and the roofer's proposal on the Roofing/Construction
Questions forum at:
The roofers there seem knowledgeable and helpful to homeowners.
I WOULD be concerned about the weather and temperature conditions under
which the roofer intends to do the work. To properly seal (and that's
the whole point of WinterGuard) it must be put on a dry deck above 40
degrees F. If it were me, I'd talk to the roofer about that before
giving him the go-ahead.
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