Ice dams

Jack

I've written of this before, but in light of what you poor folks are going through in the frozen north I thought I'd share it again. My last winter in MA was '11. I was closing on the sale of my home the end of Feb. we had one big storm a week for 5 weeks. There was no where to put it then, but I think not as bad as it is now. Anyway, for the first time in the 19 yrs I owned that home I had ice dam/water damage issues. Once I repaired the insulation the contractor removed, I knew I had to deal with the snow load as well as the ice. I shoveled off the roof and had at least a 12" tall iceberg across the roof and gutters. Everyone in town was looking for anyone who would get up there and beat the H*** out of the ice. In the process they damaged gutters and shingle tabs. I had to do something as I was afraid the new gutters we're going to carry away.

I grabbed 100' of garden hose, hooked it up to my R85 tankless service valves with a nozzle that gave a shower head type pattern ( max contact with the ice), began at the downspout end and cut 18-24" " bread loaves" from the outside in (so the water wouldn't pool). Once that was done the length of that pitch the rest was easy getting the remaining ice melted. I ran hot water for 3 1/2 hours and never ran out of hot water. The run-off melted most of the ice in the driveway. When I was done that roof looked like a summer day and no damage.

The neighbors we like, "what's he up to now?"

Snowmelt

Nice story, how high was the roof, I had a costomer who had about two inches of ice on his driveway last year. I fixed his water heater and then he used it to unmelt his driveway. I don't know how it turned out but hey it worked.

Jack

Two story on the front, three on the back...but hey, if I fell I was going to land in about 6' of snow. Fact is, I've always been comfortable at heights. Having done a lot of rock climbing, I know how to tie myself off. Also, on power houses, refineries, etc I always volunteered to go up top.

I take it as an act of kindness that you, Snowmelt, would be first to respond to this thread;)

Snowmelt

Your welcome.

icesailor

Jack did a fine thing.

For others, be extremely aware with spraying hot water on roofs to get the snow off. If you do it, start at the bottom and melt up. Water weighs 8.33 per gallon and if you spray the water up in to the snow, and it isn't immediately running out, it will be held by the snow and you can collapse a roof. Easily.

Cold water works almost as well as hot water. Its just slower and cheaper. Do it as a inverted "V" with the point up. That way, the water has a larger area to run out of.

If you look and notice, Northern Tier houses often have black mold growing on the underside of plywood roof sheathing above the wall plate because of the heat flowing out of the ceiling and through the insulation. The dew point and temperature warms the first 4' of sheathing causing condensation. The closer to the edge of the room, the worse it is. Its what makes ice dams.

Gordy

Ice dams are not always an indicator of poor design, or insulation. Weather patterns, and solar influence can promote ice daming well.

Abracadabra

icesailor said:

.....
If you look and notice, Northern Tier houses often have black mold growing on the underside of plywood roof sheathing above the wall plate because of the heat flowing out of the ceiling and through the insulation. The dew point and temperature warms the first 4' of sheathing causing condensation. The closer to the edge of the room, the worse it is. Its what makes ice dams.

I thought ice dams were due to snow melting on the roof and then refreezing above the eave? Which is exacerbated when the attic has poor ventilation and insufficient insulation, leading to a warmer attic and more melting snow to refreeze above the eave.

Gordy

Abracadabra said:

I thought ice dams were due to snow melting on the roof and then refreezing above the eave? Which is exacerbated when the attic has poor ventilation and insufficient insulation, leading to a warmer attic and more melting snow to refreeze above the eave.

Not always. When you start seeing long stalagmites off the gutters there is an insulation issue deffinetly.

You really need a poor insulation detail to promote that. What Ice is saying is true though the lower the roof pitch the more the effect because the roof is closer to the ceiling insulation in that 4' area by the exterior wall. The warmer air does not get cooled by lower temp attic air before it hits the backside of the roof. Of course poor soffit ventilation would have an effect too.

icesailor

Abracadabra said:

icesailor said:

.....
If you look and notice, Northern Tier houses often have black mold growing on the underside of plywood roof sheathing above the wall plate because of the heat flowing out of the ceiling and through the insulation. The dew point and temperature warms the first 4' of sheathing causing condensation. The closer to the edge of the room, the worse it is. Its what makes ice dams.

I thought ice dams were due to snow melting on the roof and then refreezing above the eave? Which is exacerbated when the attic has poor ventilation and insufficient insulation, leading to a warmer attic and more melting snow to refreeze above the eave.

It does. And something that can foretell ice damming is the black mold on the underside of roof sheathing at wall/plate points. There's enough heat given off that ice or moisture will form on the underside of the roof. Soffit vents are supposed to help with this. It doesn't always.

Gordy

Gutter gaurds depending on the design can have a profound effect under the right conditions also. They are great for keeping the crap out of the gutters, but can cause issues when freeze thaw cycles plug the gutter gaurds up.

BobC

The problem I see is a collection of housing that is approaching a 100 years old with questionable insulation that has been subjected to 8 ft of snow in under a month. Add to that it has not been above freezing for several weeks. Many homes are surrounded by seven or eight foot berms of snow so accessing the roof is almost impossible.

This is the worst I've seen in over 60 years. Spring will come but I hope it does so carefully or our basements will all be full of snowmelt.

Bob

Jack

Have had trouble with this link, but go to U-tube "snow rake & slide" Very cool.

BobC

That's really cool.

Bob

Gordy

Steep pitches I hope on those 100 plus year old dwellings.

KC_Jones

Gordy said:

Steep pitches I hope on those 100 plus year old dwellings.

In the area I live most of them are steep 10 /12 to 12/12 is quite common. I have often wondered if this was done for weather related issues. Snow loading and more effective shedding of the rain.

Gordy

Yes steep roof pitches have that ability by design. A frames were designed for function not achieving a look. All though they do look pretty cool.

MikeG

I agree with Gordy that ice dams are not necessarily a design or poor insulation issue. I have a gambel style roof on my unfinished garage in NW Ohio. Roof faces north and south. Dark brown shingles. Vented soffits. No insulation. Full floored upstairs, no heat, roof vents, basically totaly open to outside temps. The snow will cover the roof, more on the upper low pitch section and the very bottom 3 foot wide section. 0 degrees with full sun last Sunday and the snow was melting on the steep section and some on the upper section, running down and refreezing. The gutters were a solid block of ice. A perfect recipe for ice damming, but definitly not a heat loss issue. I just reroofed the garage and house last October after 29 years on an 25 year roof. No water damage or issue with the plywood. That roof only had the standard (at the time) of 15# felt dripe edge and asphalt singles. So this time I put ice guard 3' wide along the eves and 18" along the rakes and synthetic underlayment with a 30 year fiberglass shingle. Should never have an issue and should lastg my lifetime. I do hope to insulate the garage this summer since it is attached to the house. It wont be heated though.

icesailor

You can buy Frostex electric heat wire and flop it in the gutter. Turn it on and it will melt the ice. Part of Ice Damming is the gutters filling up with water and the ends of the drip edges end up in the ice. Frostex is cool. You put your own (provided) plug on the end and it comes in a roll. After cold weather, just roll it up for next year.

Also, the old Yankee woodpecker/roofers always put a "Water Table" lap on the first course where the roof singles overhang whatever the starter strip is. So that the water drips off the end of the roof shingles and doesn't use the "Drip Edge" to be where the water drips from. That lets the water run back through capillary attraction. It runs back like solder into a joint.

hot_rod

An issue we had in then mountains when we had big snow years was the un-equal loading on the roofs. Even though they were designed for high snow loads, wind would often blow one side clear and load several feet on the opposite side.

That presents some really biased loads on the framing and structure.
The building department would issue warnings about clearing your roof when we had big dumps and windy conditions.
I lived in Little Cottonwood canyon for a number of years in the 70's, average snowfall was just under 500" in those years. I got a lot of roof shoveling and cornice busting experience.

One of the few places the building departments allow entry doors on commercial and public buildings to swing in.