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5Jan/11Off

Dam, an ice dam

Source: The Daily Apple

We must have had just the right weather in Minneapolis because icicles have started to form all over houses in our neighborhood.  As pretty as they are, they pose a pretty big threat  - ice dams.  An ice dam forms when snow melts off a warm roof but freezes as it reaches the eave (overhang).  The ice builds up and the melting snow forms a little lake behind the ice.  It's not a lot of water but it's enough to creep back up under the shingles and eventually run down into the walls and ceiling.  This image from homeconstructionimprovement.com illustrates an ice dam.

There's evidence of water damage from ice dams in the past in our living room and foyer.

Water spot around the crown molding
The wall is bowed from water above the front door and window

We hadn't seen any problems until just last weekend.  The temperature was above freezing and we were greeted by drips of water coming from the window frame and door frame.  Yikes!

Icicles on the inside of our door frame :(
Ice in the bottom of our door - which froze shut

Our neighbors told us that previous owners in the 90s spent a lot of time trying to figure out a water problem coming from the roof.  Supposedly they fixed the problem but clearly there's still water coming in by this door.

How to fix Ice Dams

If both the roof and eave are cold, the snow stays frozen and doesn't cause a problem.  If both the roof and eaves are warm (like in the spring) then the snow melts but runs right off the roof.   What you don't want is a warm roof and cold eaves.  To fix this you either need to make your roof colder, your eaves warmer, beef up your roof's defense against water, or get rid of the snow all together so there's nothing to melt.

Keep your roof colder
The reason the roof is warm is because there's not enough insulation  - or none at all.  If you look around your neighborhood and see snow on your neighbor's roofs but not on yours, you probably don't have insulation.  If you have snow on your roof except for a few patches where it's melted, those patches are the places you don't have enough insulation.  Better roof ventilation can also solve this problem by allowing cold air to circulate through the attic and keep the roof cold.  We have pretty good insulation,so when there's snow on the ground, there's still snow on our roof.  Our insulation compares well against neighboring houses so it's not our inside heat that's melting the snow on our roof and causing the excess water.

How ventilation keep the roof cold. 
Source: bellseamlessgutters.com

Keeping your eaves warmer
Another remedy is to keep your eaves warmer so the melting snow doesn't turn to ice.  You can buy heated de-icing cables that run along the edge of your roof and down the gutter.  It keeps that section of roof warm and keeps ice from forming.

source: unitedhomeexperts.com

These might work but they don't solve the bigger problem - heat is escaping your house through your roof.  It's a bummer if you're paying for heat that's floating out the roof but it's a bigger bummer to pay for more heat to keep the eaves warm.  Since we're not loosing a lot of heat from our roof, we might try to install these this summer in some key spots to see if this helps next year.

Beef up your roof's defense against water
There's a product called "Ice and Water Shield" that you can have installed when you're having your roof replaced.  It's a thick, sticky, waterproof barrier that makes the bottom few rows of shingles totally water proof.  You can have standing water backed up from an ice dam and nothing will get into your walls and ceiling.  We mentioned our previous owners did something to fix the water damage, I'm hoping this is what they installed.  Unfortunately, if they did not, we probably won't be doing this any time soon since the roof is new enough that we don't want to mess with it.

source: homerestorationsmd.com

Get rid of the snow all together so there's nothing to melt
Finally, if there's no snow to melt, there's no possibility of water freezing.  You can buy long (like 20 feet) shovels that are designed to pull snow off your roof.  We found one in the garage after moving in (yay for free stuff!) so I broke it out.  Our roof is well insulated so we shouldn't have major problems with ice dams... fingers crossed. Our best line of defense right now is just to minimize the amount of snow on the roof.

The culprits
My what long... shovels you have.
"Reach for the sky!"
Avalanche!

Even with these defenses there are times when the weather is just right for making ice dams.  On a 32° day with lots of sun it's almost inevitable. We'll see how many water problems we have when spring hits.  Our plan for now is to keep shoveling the roof (only in Minnesota would you hear that...) to minimize the amount of snow that can melt and cause problems.  We've discovered that the tree in the front yard which we already don't like (blocks light and pathway to the front door and is kinda overgrown and ugly) makes this shoveling process extra difficult.  Looks like we have another project for the spring!  Oh the joys of owning a home.

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  1. I found last year that putting nylons full of ice melt/salt in our gutters really helped stop our ice dam issue. We have multiple roofs on our 100+ year old house and can't reach the roof over the main part of the house (2 stories). So to try and stop my husband from punching more holes in the shingles with the screwdriver every time he decided to chip the ice dams out I filled up the nylons and placed them over the ice in the gutter and boy did that help. We didn't get them up there until the end of January last year and since we had such an early Spring in WI last year we never did have to refill them. I have been trying to get him to put them back for this year but so far he is fighting me, apparently he thinks that money to replace the roof is going to come out of my butt or something. ;) Love your blog by the way.

  2. That's a great idea! I used a shovel to throw ice melt out our upstairs window onto the ice but that felt reayll ghetto! Call my crazy but I think nylons full of salt is the better option :)

  3. I hear you our house had major ice dam issues! Every single room had water stains on the ceilings and they were 2' wide in one room! The previous owners had went with cheap 10 year shingles and they were over 80% nail pops on one side of the house. (The nail pops come from the ice damns.) When we bought the house we worked out that she would pay to put on a new roof and I speced out the shingles and ice & water shield. The ice and water shield should be 7' up past the exterior wall (not including the overhang which should also have it). Also a ridge vent can significantly help with even air flow. We had side vents and it was easy to convert it when we had the new roof put on.

    But insulation is the best thing you can do. Our home was only an R-10 and we re-insulated it to an R-48. We haven't had any ice daming issues since. You live near the twin cities right? According to ASHRAE Standard 90.1 you should have a min of R-38 in your attic. I have a list of insulation types and their R-values on my blog:
    http://threeacres.wordpress.com/2009/11/13/going-geothermal-part-3-calculating-residential-heating-and-cooling-loads/

    Adding some more insulation (if it can fit) doesn't cost much, will help you be more green, save on heating and cooling bills, and reduce your chance of ice dams happening in the future. Plus attic insulation has the shortest return on investment according to many studies.

  4. Thanks Robin! That's really helpful info. I don't have access to any attic space since we have a story-and-a-half. I can say that the roof is insulated enough that snow doesn't melt unless it's above freesing outside. If we have major problems with water in the spring we'll have to open up the ceiling to add venting and more insulation.

  5. Hi! I just came across your blog by way of Hip House Girl. I am not sure what exactly made me click on your name….but it turns out you're fellow Minnesotans, so I am glad I found you guys. I must have been able to sense how incredibly cool you were…or I am just a chronic linker. We started our blog (check it out!) right after we got engaged. We're in the throws of a DIY wedding so I really enjoyed reading about your wedding projects. Best of luck with that roof shoveling. We're renters for now and it's at times like this that I am rather thankful for that. ;) But I nanny for a family in Mpls and they have had great luck with the nylon ice melt combo.


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