Category Archives: House

Preventing Ice Dams (Part I)

So, after last year’s ice dams, I’m working to try and avoid them with pre-emptive actions to take care of the problems. Some of these will be inside the house, and others outside.

Inside, one of the things I need to do is empty the four rafter cavities that are over our son’s bedroom closet (below the attic floor) of the blown-in insulation, and try to use some rigid poly insulation that will allow air to come up from the eaves under the roof. This will go along with replacing the plaster and lathe with drywall, to take care of the water damage we had there.

The other thing I need to do is patch the places where the previous owner had the ‘master’ bathroom replaced. In order to run some electrical wires, the contractors they used put a big hole in the back corner of the plaster of the room, which they covered with a soffit over the shower. The thing about this hole, and the hole I assume is at the bottom of the wall, is that warm air from the house goes right up behind the shower and up under the base of the valley on the back of the house where we had the worst ice build-up. I’m still debating the best way to fix this problem, either from the attic above, or from getting into the soffit from the bathroom.

Outside, I’ve worked up a plan to run heating tape/wire along the eaves, gutters, and valleys where we had problems (and in the front where we also get ice build-up). This involves running wire to outlets to the exterior in the areas the tape will be located, and installing GFI plugs in these. Luckily, the finished room in the attic contained a 20amp, 240 outlet which we never used. I say luckily, as it was wired incorrectly for a 240 outlet (no return line other than the ground!), but after disconnecting it in the breaker box, it was a nice dedicated 12 gauge 110 line available in the attic, with enough extra line up there to install a junction box.

From the junction box, I need to run two lines, one to behind the valley over the shower, and the other to the front of the house. Each of these will be placed under the eaves of the roof, which will allow for the plugs to be protected from the weather, and to give a ‘drip loop’ to the wires which will insure that if water IS running down the wire, the lowest point of the wire will be below the plug/outlet.

The back area has two problem spots, and covers 137 feet of eaves, three valleys, a skylight, a small 4’x4′ first-story roof, and three downspouts. The eaves come out about 16-18” and have a split-slope, where the two feet of roof closes to the eaves is a more gentle slope than the rest of the roof. In dealing with that, I planned for 24-28” of coverage of the eaves, full gutter coverage, and six feet (or so) of coverage up the valleys with the heat tape/wire.

Frost King has a formula for figuring out how long of a wire you need for your task, and a couple of minutes of work made it an easy spreadsheet. Not surprisingly, I needed more than one length of wire for this set-up. Frost King offers wire lengths from 250′ to 50′, so I ended up with a combination of one 200′ length and two 60′ lengths, with one 60′ length dedicated to most of the gutters and two downspouts, the other 60′ length dedicated to the short section of roof (over our son’s closet), one of the valleys, the rest of the gutter and the last downspout, and the 200′ length to cover the rest of the eaves, the skylight and the other two valleys.

In the front, there is only one little section of eaves, and a long, winding gutter with a feed from the first story roof over the entryway, so a 60′ length will take care of the area, with a loop making sure the entryway roof outflow is clear.  And all of these will need the self-regulating, temperature sensitive plugs so that they’re only on when they need to be.

 

 

(Actual installation information in Part II)

Ice Dams

An ice dam is an occurrence where a ridge of ice forms along the edge of a roof such that melting water under the snow is blocked form leaving the roof by the ridge of ice.

Anatomy of a simple ice dam.
Anatomy of a simple ice dam.

 

Our roof has an area where ice dams form in a valley of the roof where water is channeled, which when it rains, is just fine. But in a longer, colder, snowier winter like we’re having this year, snow that is heated by heat from the house, or by the sun’s meager heat, melts and then refreezes as the cold gets to it.  In most places on our roof (even other valleys), this isn’t a problem, and the water refreezes as icicles.

 

Small icicles are a result of small amounts of melting where the water flows under the snow, and freezes where it reaches the colder edge of the roof or gutters.  But with an ice dam, the water sits behind the ridge of ice at the edge of the roof and freezes there, raising the height of the ridge, and producing a shelf of ice that goes back along the roof.  If this goes on long and far enough, the melted water backing up behind the ridge/shelf of ice gets up in under the shingles, and the heat of the house can keep this liquid and allow it to flow in under the shingles, through the roofing materials and into your walls.

 

Ours is bad due t several factors.  First, the valley is a place where you are more likely to get a larger amount of water.  Second, our house is old (built in 1898), and wasn’t designed to be heat efficient, so heat gets to the roof more (though, if we had some serious coal heat, it would probably melt all the snow as it fell …).  And third, the people who owned the house before we did had the bathroom just under the valley redone, and the contractors took out a bunch of the plaster, leaving an open space for hot air to go right up in under the roof and heat the snow just on the outside so the water flows down to the colder roof and freezes.

 

The major way to deal with an ice dam is to carve a channel through the ice to allow the backed up water to escape.  The first step toward doing this is to clear the snow away from the dam and as far up the roof from it as you can, because snow not only can melt to make more water, but also provides a layer of insulation that allows your roof to be warmer which can also lead to more water.

 

The second step is to cut the channel.  A relatively quick and easy way to do this is with a steam-cleaner.  I used our Wagner 915, and it worked well, though with 8-10” of ice, it took several tankfulls of steam to cut channels and remove a large section of ice in the valley.

 While this might seem slow, it is really safe for the roof, unlike trying to use a propane torch, heat gun/paint stripper, or even a hammer or hatchet.

 

Another option is to use calcium chloride (which melts ice at -25 degrees F), magnesium chloride (which melts ice at 0 degrees F), or rock salt (which melts ice at +25 degrees F) as a melting agent that is laid on the ice in a line to melt a channel. An easy way to insure that you have enough in the right place is to fill am old stocking or one leg of an old pair of pantyhose with the melting agent, and lay it so that it crosses the entire ice dam from the roof above the dam to where it can just hang over the edge.  This will ensure that you melt a nice channel down through the dam, and if you have enough of a melting agent in the stocking, it can keep the channel open even after further snowfall and melting.

 

These channels, once opened up, allow the new melt-water to make it over the edge of the roof, perhaps giving you icicles, but keeping it from building up and causing damage inside the house.

 

There are some preventative options.  Home Depot offers some calcium chloride bricks that you put up on your roof where you normally get ice dams before it snows and they will melt the snowfall and keep it liquid as it runs off the roof.  They are supposedly good for 12″ of snow before needing to be replaced, but realize that that’s about an inch of rain, if you are in a location that might go back and forth between liquid and solid forms of precipitation.

 

Another option would be to get a ‘heat tape’ or ‘heat line’ to run along your roof and gutters.

  Most all of these are ON as soon as you plug them in, so there are some temperature-based controllers that will turn them on when the temperature drops below a certain threshold, and turn them off when the temperature warms up enough, thus saving you on electricity costs, and from overheating your roofing. 

These lines are clipped to your shingles and are usually run in a zig-zag along the eaves to provide channels over the cooler overhang parts of the roof.