Reuben's Home Inspection Blog

How to prevent ice dams from the exterior

By In Ice Dams - How To Prevent On March 4, 2013


I’ve written about how to prevent ice dams by fixing attic air leaks and insulation, as well as several hack methods showing how to remove ice dams, but I still get a lot of questions about ice dam prevention.  For homeowners with a one-and-one-half story house or a house with a vaulted ceiling and no true attic space, correcting attic air leaks and insulation can be an extremely expensive project.

In these cases, it’s not always cost effective to fix the problems that are causing the ice dams – the ‘repairs’ might outweigh the costs of controlling the ice dams, and even if the repairs make economic sense, it’s not always in the homeowner’s budget.  In those cases, I recommend ice dam control from the exterior.

Remove The Snow

Roof RakePulling snow off the roof with a roof rake will keep ice dams to a minimum. This becomes a constant chore, but it’s better than dealing with water leaking in to the house.  Just raking the first several feet of snow from the eaves is typically enough to prevent the formation of ice dams, but in some cases, this will cause ice dams to form higher up on the roof.  The trick is to get the shingles exposed to the sun; once that happens, the sun will warm the shingles enough to prevent ice from accumulating.

Raking snow off the roof with a roof rake is a safe way of removing snow, as long as you don’t get too close to your overhead power lines.  In theory, a roof rake could cause some premature wearing of shingles by removing the aggregate, but I’ve never seen any real life evidence of this.  Some roof rakes have little wheels at the bottom that prevent the rake head from actually rubbing on the shingles.

Roof Rake

While the roof rake pictured above is the most common type, there are many other variations of this designed to make the work easier – one such version is the MinnSnowta Roof Razor®.

Removing snow from the eaves is an effective way to prevent ice dams, but it won’t work 100% of the time.  Two years ago, I inspected several houses with ice dams forming right where the snow stopped being removed.  This is not typical, but it can happen during especially cold, snowy winters. When this happens, people start to get depressed and wonder why they live in Minnesota.

Second Ice Dam

The fix for this is to have all of the snow removed.

For two-story homes where using a roof rake from the ground isn’t practical or possible, the options are to risk your life getting up on an icy roof to shovel the snow off, hire someone else to risk their life, or install roof de-icing cables as a preventative measure.

Shoveling snow off roof

De-Icing Cables

Roof de-icing cables, also known as heat cables or heat tape, should be considered a last resort when it comes to preventing roof leaks from ice dams.  De-icing cables themselves aren’t cheap, it costs money to have them professionally installed, and they’ll cost money to operate – between five and eight watts per foot.  I’ve also heard that they can damage shingles, but I’ve never seen any evidence of this.

Roof De-Icing Cables

On the flip side, de-icing cables are very effective.  When de-icing cables are properly installed and operational, ice dams won’t cause leakage.   De-icing cables won’t prevent the formation of ice at the eaves, but they’ll keep enough ice melted to create drainage channels for water.

If you choose to install roof de-icing cables yourself, here are a few tips:

  • Measure the areas where you need to install your de-icing cables first, and buy appropriately sized cables.  For a simple 15′ section of roof with no overhang, a gutter, and one downspout with an extension, you will need a 60′ heating cable.
  • The cables should extend 6″ up the roof past the exterior wall line, through the gutters and downspouts, and 2/3 of the way up the valleys.
  • Don’t bother removing the snow from your roof; you could damage your cables, and you could potentially create another ice dam higher up on the roof, defeating the purpose of the heating cables.
  • Don’t expect the snow and ice to melt the way it does in the promotional photo above.  It’s like comparing a photo of a fast-food burger to the burger that actually comes in the fast-food bag.

If fixing the causes of ice dams isn’t a possibility and safe removal of snow isn’t possible, de-icing cables or de-icing panels may be a good choice.  Sometimes this is the most cost-effective way to prevent roof leakage from ice dams.

Author: Reuben Saltzman, Structure Tech Home Inspections  Google Profile

          


About the Author

Reuben

Reuben is a second generation home inspector with a passion for his work. He grew up remodeling homes and learning about carpentry since he was old enough to hold a hammer. Reuben has worked for Structure Tech since it was purchased by Neil in 1997, and is now co-owner of the company. Reuben’s favorite customers are the ones who have a lot of questions; he grew up thinking he was going to be a school teacher because he enjoyed teaching others so much. In a sense, that’s a lot of what home inspections are about, so Reuben truly does what he loves. Reuben has an A.A. degree in liberal arts and has attended most of the Building Inspection Technology classes at North Hennepin Community College. Reuben and his wife are the proud parents of two young childen, Cy Alexander and Lucy Nicole, and have a German Shepherd named Stanley. With two young children Reuben doesn’t have much free time, but he still tries to play disc golf as often as possible during the summer. Reuben lives in Maple Grove, MN. Professional Qualifications / Memberships: *ASHI Certified Inspector *President, ASHI Heartland Chapter *Member, Minnesota Society of Housing Inspectors (MSHI) *Licensed Minneapolis Truth-in-Sale of Housing Evaluator *Licensed Saint Paul Truth-in-Sale of Housing Evaluator *Licensed Maplewood Truth-in-Sale of Housing Evaluator *Licensed Hopkins Truth-in-Housing Evaluator *Licensed Robbinsdale Point of Sale Evaluator *Affiliate Member, Southern Twin Cities Association of Realtors

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1 Comment

  • Jennifer 2 YEARS AGO

    I appreciate this post, as it is so detrimental to home owners to properly remove snow and ice from their homes. This is obviously more important in some areas then in others, but your techniques look safe, and gets the job done. I like that you posed pictures with your instructions as I am a visual learner. Thanks again!