Question about snow on roofs

[FTL_Ian]

Anyone know how cold it should be outside before one does this?

depends on the situation

you could post pictures of your roof for guys to guess what is going on. Do you have any leaking inside the roof? Do icicles cause problems? I like getting snow of the roof if it is easy ... why not? In most cases I doubt you need to. Your house has been ok so far. Some old guys in NH have nothing better to do than pull snow off ... it might not be important.

You're probably right.  We made it through last year okay.  That said, it does appear that I have some ice dams...

[alohamonkey]

me too . . . i thought they would melt like they did last year but it looks like the ice just keeps building up.  i was trying to toss some de-icer up there this morning but there has to be a better way to take care of them.  any suggestions?  my friend told me to just get on a ladder and start whacking them with a hammer. 

[Nat F]

me too . . . i thought they would melt like they did last year but it looks like the ice just keeps building up.  i was trying to toss some de-icer up there this morning but there has to be a better way to take care of them.  any suggestions?  my friend told me to just get on a ladder and start whacking them with a hammer. 

If it's a question of damaging your roof through ice dams or removing the ice then go ahead and whack it.  However be aware of the chance of damage to the roof and shingles by doing so.  Shingles can be torn or damaged either by the hammer itself or by the shingle sticking to the ice and being removed with the ice.

You should also consider removing the snow on your roof since so much has fallen so early in the season.  First it will melt and contribute to the water and ice dams, and second if it rains while the temp is just above freezing and drop below freezing again the weight of the snow/rain/ice combination can cause your roof to collapse.  It's not normally an issue but this has been a heavy snow season so far and rain followed by freezing temperatures is forecast for Sunday & Monday.

-Nat

[alohamonkey]

thanks . . . and i'm leaving on vaca tomorrow morning . . . might just have to cross my fingers

[Bald Eagle]

Lloyd and I had to remove shingles from a house in Grafton so we could install an exhaust for the hot water heater and a vent pipe for the plumbing.

We just pounded on the ice dams with a hammer and they eventually crumbled away.

We've got some very flat roofs that extend out over the porch, and they built up nearly 2 feet of snow.
You can just do what Tom Sawyer said and leave a wall around the edge - worked for me.
http://newhampshireunderground.com/forum/index.php?topic=12540.0

The faster you uncover some of the black shingles, the faster heat will be absorbed and melt some of the ice & snow off the roof.  If you're going to use a shovel, I'd recommend one without the metal edge along the front, and shovel downwards and with the shingles, not upwards in case you catch the edge of one.

It would be an interesting construction feature to be able to use the used warm/hot water from laundry/dishwasher/shower to melt or rinse the accumulated snow off the roof...  Maybe just run it through an open drain pipe under the roof to transfer heat - the pipe is never full of standing water, so it won't freeze and build up pressure.  Kind of like solar water heating pipes, but in reverse.

[KBCraig]

http://www.unionleader.com/article.aspx?headline=Rain+may+threaten+roofs%2c+roads&articleId=5c0ea106-7d6f-4eb1-87c0-f5db29986813

Rain may threaten roofs, roads

By STEPHEN FROTHINGHAM
The Associated Press

CONCORD – State safety officials are concerned that rain forecast for tomorrow -- coming on top of several feet of snow that's fallen in parts of the state in the last week -- could lead to collapsed roofs, road flooding and black ice on highways.

They are urging residents and officials to take precautions before the rain arrives.

The National Weather Service was forecasting anywhere from a tenth of an inch to three-quarters of an inch of rain tomorrow. In some areas, it will be frozen rain.

When the rain soaks into the snow and then freezes, it will create an icy concrete that homeowners may have to live with until spring.

If the frozen layer is allowed to build up on roofs now, later snowfall will be difficult to remove and could collapse roofs, said Rob Farley, the state's deputy fire marshal.

Officials recommend using roof rakes to clear roofs from ground level.

Farley recommends home and business owners and municipal crews get out today to clear around fire hydrants, fire lanes, drainage ditches and culverts. Homeowners should clear all exit paths from their homes.

"It's easier to do it now than after this added weight is added to the existing snow," Farley said.

After the week's snow was cleared from travel lanes, highway crews started "winging back" the snow banks to improve visibility and leave room for the next storm, state highways spokesman Bill Boynton said.

"Where we put snow is starting to become an issue," Boynton said. He urged drivers to use caution at intersections and at highway onramps, where high snow banks reduce visibility.

Crews also are preparing for the rain, he said. "They are punching holes in snow banks to create drainage possibilities," before the rain arrives.

Looking forward to next week's Christmas vacation, safety officials also are warning parents to make sure kids are well away from roads when sledding or building snow forts and tunnels.

And Fish and Game Department officials warn that ice conditions are still unpredictable on lakes, ponds and rivers, in part because recent snows have insulated ice, preventing it from thickening as fast.

Fish and Game Maj. Tim Acerno says at least 6 inches of solid ice are needed to support walkers. Eight to 10 inches are needed for snowmobiling. People venturing out on ice should check it carefully.

"Don't assume a snowmobile track going across water is safe just because it's there," Acerno said.

Everyone should stay off ponds and lakes whose water levels fluctuate because of dams, Acerno said. Ice on Andover's Highland Lake, where a dam is being repaired, should be avoided, he said.

[John Edward Mercier]

me too . . . i thought they would melt like they did last year but it looks like the ice just keeps building up.  i was trying to toss some de-icer up there this morning but there has to be a better way to take care of them.  any suggestions?  my friend told me to just get on a ladder and start whacking them with a hammer. 

The de-icer (which is probably calcium chloride) will do the job. A modern roof will have an ice shield membrane under the shingles to prevent water damage.

[Riddler]

There's a short description of this in the NH Underground Moving Guide:

If your roof is poorly insulated or poorly ventilated, it will tend to form ice dams. What happens is the heat flowing to the shingles melts the snow, and flows down to the edge. At the edge, it contacts the open air and freezes, forming an ice dam. This dam backs the water that is still flowing down up under the shingles, and can soak into the roof interior, ruining insulation, sheet rock, etc. This snow will melt a lot around chimneys, sky lights, and above where can lighting is mounted in the ceiling of the top floor.

If this happens, you need to get a snow rake with long extendable handles and rake the snow off the roof.

Also, remove the gutters in the fall, as they will tend to fill up with ice and exacerbate the problem.

Related to potential house damage from snow, they also said:

Yes, if you live in a house with plumbing through outside walls, or with poor insulation, you should leave your faucets open a crack to drip. This isn't to keep the water flowing, it is to allow any ice building up to have some place to push the water. Ice forming in the pipe will take up more space than the water it is made from, so it will expand linearly along the pipe and cause water pressure to build up if you don't give that trapped water some place to flow. It isn't the ice that breaks the pipes, it is the pressurized water.

what crack-smoker came up w/ this?
copper water piping can handle several HUNDRED psi....
it IS the expansion of frozen water that splits piping...
been there/done that 24+ years (professionally)

[alohamonkey]

Lloyd and I had to remove shingles from a house in Grafton so we could install an exhaust for the hot water heater and a vent pipe for the plumbing.

We just pounded on the ice dams with a hammer and they eventually crumbled away.

We've got some very flat roofs that extend out over the porch, and they built up nearly 2 feet of snow.
You can just do what Tom Sawyer said and leave a wall around the edge - worked for me.
http://newhampshireunderground.com/forum/index.php?topic=12540.0

The faster you uncover some of the black shingles, the faster heat will be absorbed and melt some of the ice & snow off the roof.  If you're going to use a shovel, I'd recommend one without the metal edge along the front, and shovel downwards and with the shingles, not upwards in case you catch the edge of one.

It would be an interesting construction feature to be able to use the used warm/hot water from laundry/dishwasher/shower to melt or rinse the accumulated snow off the roof...  Maybe just run it through an open drain pipe under the roof to transfer heat - the pipe is never full of standing water, so it won't freeze and build up pressure.  Kind of like solar water heating pipes, but in reverse.

Thanks for the advice.  Luckily Mother Nature helped me out while I was out of town.  Most of the ice jams melted.  I've been trying to melt some of the snow/ice in my backyard and I thought of another interesting construction feature.  I've built a fire in my back yard and thrown ice and snow around it but it didn't melt it nearly as well as the exhaust from our dryer.  The air pumped out of my dryer vent has helped me melt pounds and pounds of ice and snow in the last two-three days.  I wonder if there would be any easy way to redirect dryer vents to the lower portion of a roof to take care of ice jams.  Or would it lose its heat too quickly.  I'm pretty clueless about construction as this is my first house but it was just something I thought about. 

[srqrebel]

Luckily Mother Nature helped me out while I was out of town.  Most of the ice jams melted.

Nice... I take a vacation to Florida, and it warms up in New Hampshire.

This morning I spoke with a lady who had just gotten back from visiting NH, and she told me it was 50 degrees there on Sunday!

[alohamonkey]

Yeah . . . I was outside working on the house in only a long-sleeve t-shirt today.  I thought about my idea that i posted earlier and realized that would require extensive duct work.  I'm thinking about jerry-rigging something to the outside of my house going from my dryer vent up to the area that gets the biggest ice jams.  It won't look pretty buy maybe it would help. 

[kola]

invest in metal roofs.

[Lloyd Danforth]

Agreed!  Some of the metal roofs aren't too ugly, either. Another alternative is to cut out the first couple of feet of shingles above the eves(gutter line) and install flashing along the bottom of the roof.

[Riddler]

Yeah . . . I was outside working on the house in only a long-sleeve t-shirt today.  I thought about my idea that i posted earlier and realized that would require extensive duct work.  I'm thinking about jerry-rigging something to the outside of my house going from my dryer vent up to the area that gets the biggest ice jams.  It won't look pretty buy maybe it would help. 

your ideas re: extending dryer vent, are not sound. You always want the shortest poss. vent length, as they do accumulate lint & require cleaning
at some point. A very lengthy vent run (up to the roof line, as you propose, would add significant restriction to the proper air flow necessary to dry your clothes. You would find that it takes much longer to dry clothes with a lengthy vent run. Prob. not very good for the dryer, also. Ask an appliance store & see if they don't echo my sentiments.
Elec. roof cable is the way to go here.

[MaineShark]

what crack-smoker came up w/ this?
copper water piping can handle several HUNDRED psi....
it IS the expansion of frozen water that splits piping...
been there/done that 24+ years (professionally)

Several thousand, actually.

The weakest point is the soldered fitting, particularly in old pipes with lead solder.  That's likely where the story comes from.

Of course, if someone has bad (acidic) water that has weakened the piping, then all bets are off.  I've seen copper pipes so flimsy that you could poke your finger through them.  Water pressure could definitely burst weakened pipe.

Joe