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New Roof and Ice Dam Prevention - One Family's
[Update: the winter of 2004 was another ice dam year. I
received several inquiries so I added
an update section. In 2019 I came across a
1977 U of Minnesota Extension booklet on ice dams. Very
little has changed since then!]
In the winter of 1997 we experienced severe ice dams and
considerable interior water
damage. We had three things going against us: a severe freeze thaw
cycle, a finished attic
with inadequate knee-wall insulation, and no ice-water shielding
on the roof.
In the spring of 1997 we attempted to eliminate the problems we
could control. We
thought we chose contractors carefully. We did not take the low
bid, in fact the bid we
accepted was moderately high. Despite that, we had a number of
problems. This snippet
describes lessons learned and what we would do differently in the
future. It first
describes the steps we took to reduce future ice dams. After
reviewing what's done for ice
dams I don't think there's much real data to support most
measures. I think a metal roof
(as in French Canada) or a Scandinavian dual-roof system are
probably the only things that
really work. In fact, as of Feb1998, we again had ice dams.
Fortunately the weather was
less severe, and the ice and water shields (see below) were in
Parenthetically, I think there's a vast fortune to be made by an
establishes a national high quality, high tech, roofing solution
- In 1997 expert opinion was that stopping warm air flow to roof
areas and insulating would solve ice dam problems. In 2004 the
experts are more realistic. Some roofs and houses are so prone
to ice dams that, under the "right" conditions, ice dams will
form no matter the interventions. Old houses with complex roofs
and an attic turned into a living space are ice dam magnets.
- If you have a problem house you need to watch for early ice
dam formation, or heavy snow accumulation, and hire someone to
shovel your roof. This will cost you from $0 to $1000 a winter
depending on your roof, weather, etc; I expect it will reduce
our roof's life expectancy by 3-8 years. You can try a roof
rake, but if your roof gets ice dams chances are it will be hard
to clear by roof rake. Don't try to shovel your own
roof unless your life is worth less than $1000. Try
to phone before the shovelers are swamped with calls. If the
newspapers start talking about ice dams it's too late to find
anyone. Ideally you should ask for proof of insurance -- shoving
roofs is hard and dangerous work. Expect to pay real
- I see so little use of warming systems and wires that I
suspect they don't work -- or that it would be almost impossible
to find anyone to properly install and maintain them.
- With the preventive steps we took in 1997 (below) we end up
needing to hire roof shovelers once every 2-3 years. The real
cost is the injury to our shingles. We may tear off the top half
of our home and put in a true second story with well designed
ridge vent and soffet structures. We need the space and that
will resolve the problem. Other than tearing off a finished
attic the alternatives is probably a metal roof. Metal roofs are
getting much more popular, in the past their main weakness has
been noise, hail damage popping seams and rivets, difficulty
finding trustworth and experienced installers, and cost.
Ice Dam Prevention Steps
- Professional insulators opened up the knee wall floor boards
and blew in insulation, then covered the floor boards with
further insulation. They also installed vents in each knee wall
compartment (they entered some of the knee walls through the
roof!). I'd wanted to install a ridge vent, and have passive air
flow from a lower compartment vent up through the ridge vent.
The way the attic was finished did not allow this. (poor
design). We also considered forced air electrical vents, but
no-one here was comfortable putting those in.
- Ice and water shields 9 feet up. (Weatherwatch)
- I wanted to install a WaterFall Gutter Guard system. I'd read
that it can keep snow out of the gutters in heavy falls,
preserving a drainage area during freeze-thaw cycles.
Unfortunately our gutter installers put the gutters so close to
the shingles there was no way to install this. (May have been
limited by apron use, see below.)
- I installed new steel gutters with an apron that went under
the ice shield and shingles atop the apron. The goal was to
reduce ice flow moving up from the gutter and under the
shingles. Not sure if this will help.
- I noted ice moved up underneath our valley liner overlaps last
year. I tried to get those sealed. I don't think this was done
properly. The roofers we dealt with didn't know how to do this.
- I wanted heating tape for the valleys and gutters. The roofers
had so much trouble with the basics I gave up on this.
Lessons Learned and What I Wish I'd Done Differently
- We called a local well-known "roofer of the rich" for an
estimate. That company employs its roofers. They sent their
estimating company, which recommended another related company
for which they did the estimate. That company shares ownership
with the high end roofer, but it turned out it had few
employees. It is basically a shell company. The "supervisor"
gathered roofers and put them to work. Before signing a
contract, I should have understood the relationship of the
people doing the work to the people who ran the company.
- The supervisor had too many jobs, and was rarely available. He
was an adequate supervisor when he was available, but the crew
needed more supervsion. They had many questions no-one could
answer. Ask Who will be the on-site supervisor? How many hours a
day will he be on site? Get it in the contract!
- Ask who will do the actual work? It may not be the experienced
people you speak with, but rather people who've never been on a
roof before. You will speak with the helpful salesperson only at
the time of sale.
- Find out how problems and issues will be handled.
- Make sure everyone has in writing what contractors will do
what. Try to establish a sequence: roof, then insulation, then
indoor repairs.. Our insulation people thankfully took over vent
placement from the roofers.
- Get timelines, but be clear on what happens if they run over.
Consider a penalty clause for late completion in the contract.
Beware artificial timeline (2-3 days for "small job")
- The roofers ended up cutting our shakes to put in flashing,
and left instead an ugly insert. Be clear in the contract how
shakes and flashings will be handled.
- Read several small roofing books. (Of course we did this too
- Don't be deceived by quality of the estimator and
salespersons. May have no bearing on work quality. I'm not even
sure there's a relationship between price and quality.
- Communication can be a big problem between contractors,
workers, etc. Messages often lost or misplaced. Try to get
things written out as much as possible.
- Get full names of all salespersons, contractor, supervisor,
local supervisor. Who owns the roofing company?
- Call the National Roofing Contractors Association. Ask for a
copy of their pamphlet and a list of local members.
847-299-9070, fax 847-299-1183. This can take a while to arrive!
See about an express shipment or fax the list of local members
- Lastly, there's not much science that I can see behind what
contractors usually do. There is experience, but there aren't
the randomized controlled trials that are needed to settle
opposing views that are well argued and based on equal
experience. Opinion and experience only goes so far; this field
needs a bit of science!
Last Revised: 2/1/98. Author: John G. Faughnan.
Disclaimer: The views and opinions expressed in this page are
strictly those of the page author. The contents of this page have
not been approved by the University of Minnesota.
Confidence (1 to 3): 2. Date Created: 6/19/97. Last
Revised: 2/1/98. Expires: .
Language: english. Domain: .us. ID: 13. Topic: world. Subtopic: .
Keywords: roof; house;
home; ice dam; contractor; problems; gutter.