Ice Dams and Snow loads

I do the same here on our ranch... about 3-4 feet up. Yup, when the sun's out and warm enough, it clears that area down to dry shingles. Our gutters are dark colored on the inside and usually warm up too. Have had a few small icicles but not bad. Gutters on the back, don't get the sun so any water melted down creates ice in the gutters. I don't have heat tape in them but I do keep the snow raked off.

 

Got some work done today... Dug out the patio set and moved it so I could snowblow the patio making room to get more snow offh te roof. Widened all the pathways...dug a new path to the front so I could clear that roof.

Tomorrow I have to do a lot more roof clearing and put more rock salt stockings up on the worst dams. Water in attic but nothing coming through the ceiling thankfully.

My shoulder is on fire!

 

A lotta work isn't it? Looks good...

 

Most folks in my parts, they're heads are still spinning. We have a storm sat pm into sun then another one true into wed. Spring can't get here fast enough

 

I know some of you guys were talking about how the sun melts some of the lower snow on the roof and the ice dams are not caused by heat loss. In a case where the roof is truly cold and there are no gutters to build up any ice, why would I see ice dams forming from the bottom row of shingles if the daytime meltwater drips off the roof and doesn't get caught up in any gutters or valleys?

 

There's heat from sumthin. For sure. If it's an overcast day, temps are around 28-30, and ice is building, it's gotta be getting heat from under the eaves. So many ways for heat to get to those eaves in older homes too. Can drive ya nuts.

 

Yes, I meant that guys garage, but I have seen it in other cases as well on homes without gutters.

I believe it has to do with the way water flows through the snow. Snow holds water like a sponge, and if you think of how a sponge hold water it doesn't hold it evenly, most of the water will flow to the lowest part of a sponge and if the sponge is thick enough the top portion can actually dry out and the bottom portion will be soaking wet. The same happens with snow on a roof, as the sun warms the snow the water will flow through the snow towards the lowest portion of the roof and the snow at the lowest point will become saturated with water. Some may drip off, but if it gets cold again before much of it melts it will freeze solid and turn to ice. Next time the sun warms the snow it will begin to melt and flow down again, but this time it will hit the denser icy part, which doesn't melt as fast as the snow, and the water can't flow through the denser icy part like it can flow through snow and it gets blocked, and so the dam begins. The more of these freeze thaw cycles the denser and thicker the dam gets.
So ice dams can form without an attic heat source, but an attic heat source can create a dam without any other heat source and it can make it worse because it is more of a constant localized heat source right above the dam area, so it won't help heat or melt the dam away at all, but it will melt the snow above the dam causing water to pool and leach up under the shingles.

 

That's a great point. Water sure does work it's way down in a snow pack over time. Over time, that sure would create hard pack/ice under a snow load against a stone cold roof...

 

I just got down from shoveling a small porch roof (flat) and a slightly pitched kitchen roof. Both had some ice buildup into the gutters. The only difference being, the porch roof is a cold roof and I saw no icicles, just ice buildup in the gutter. The pitched roof looked as bad as all the rest.

 

Here are some more for you. Spent 3 more hours out there today and got more done. Took snow off the unheated garage just because its somewhat under framed and I'm concerned about the load with another foot. Spent a lot of time with the blower moving it away from the house in stages to make room for more.

The front of the house was real difficult. Melt cycles from sun had turned the top 3 inches into an icy crust that was hard to break through.

Also piles from what I raked yesterday froze solid overnight in -10 temps and I had to cop them up with a shovel before the snowblower would budge.

 

At work we have well insulated vented attics. I used a laser thermometer on the siding on one of our buildings in full sun yesterday afternoon. It registered 75 degrees. We have most ice dam issues on south facing roofs. Between roof melt-off and the siding warming the soffits and gutters, therein lies our problem. We pieced down this 12 foot icicle yesterday that was about 12" in diameter. You can see in the pic that the deck spaces has vented soffit above it. So all that warming siding is letting heat up into the attic.

The icicles around here are incredible. There are plenty that are two stories high from gutter to ground. It seems like every few houses has the pantyhose/icemelt thing at the lower rooflines.



We used a DeWalt sawzall with a short demo blade on a few ice dams, not this one. A few heavy hammer strokes to fracture the ice, and the blade just got in the crevices and shattered the ice. This saw saved a ton of labor. We are going to try a hammer drill with tile drill bit next time. The sawzall worked surprisingly well.

 

Posted in another thread before seeing this one......

got up this morning and saw some water stains on the ceiling in the living room. This is the last place I was expecting as its on the 1st floor and no plumbing anywhere above it. But it is toward front of the house which is a cape with shed dormers. Sure enough a corner of one of the dormers is right above the area with an ice dam where the upper part or the dormer meets the angled roof. I cleared whatever snow I could around it with the rake this morning but mother nature will have to take care of the ice....sometime. Hopefully its doesn't leak much any further as I will keep the area as clear as I can and the next bright sunny day try to carefully break the ice, but cant push that process.

 

I took a reading of the siding at work in the full sun under an ice dam. I think this is part of the reason we are having icing issues. That heat is working up into the vented soffit and warming the underside of the roofs.

 

Yep, just another circumstance where you can have ice damming that has nothing to do with poor ventilation in the attic or heat escaping through the ceiling.
I expect that was also at least part of the problem on the garage roof I posted about earlier in this thread.

 

Does the wind blow the snow off your roof? When it stays on the roof is when it becomes an issue.

 

That is a good question. It is pretty widespread out here.