“I’m dreaming of a crushing white death on Christmas…”
…sort of. Anyway, we’re getting heavy snowfall (for us) in southern Indiana and we’re expecting to get anywhere between 12" to 20" of snow by tomorrow evening. We’ve probably got about 10" - 12" right now, so I’ll go with the worst-case estimated snowfall. The snow appears to be powdery and the wind seems to be able to blow it from the roof of my house from time to time. What I was wondering is, should I try to drag or shovel the snow from the roof of my house in order to prevent it from collapsing under the weight of the snow? I don’t relish the idea of going outside to do this, but I’d rather do that than risk a potential collapse.
I live in a typical ranch-type house, so there aren’t any unusual peaks or anything which would allow a snow drift to build up. I don’t know what the roof pitch is, but I’d guess that for every linear foot it inclines about 5" or so. It’s not a radical pitch by any means, because I seem to be able to walk on the roof without too much difficulty. As I’ve said, the snow is powdery and seems capable of blowing and drifting. Should I be worried?
‘Heavy snowfall’ doesn’t imply weight, it implies quantity. Fallen snow is extremely light. even several meters of the stuff on your roof is nothing to worry about.
Your roof should e able to handle the snowload. Consider what happens when it needs to be re-shingled: you probably have 2 or 3 guys weighing 200 pounds or so each moving around on your roof (a dynamic load, potentially more serious than a static load of snow) and you wouldn’t think twice about the roof caving in.
Last year we had a snowfall in one storm (“White Juan”, after the hurricane that hit us in the fall) that dropped 95 cm (about 3 feet) of snow on our roof. No problems, although the radio had stories about people who had been injured trying to shovel snow off their roof… :eek:
Collapses from snow load are usually only a problem with a flat or very low pitch roof, and even then only on large structures like arenas with minimal (or no) supporting columns.
Well this makes me feel a little bit better. I’m running a slight fever right now, so going outside in the cold and getting covered with snow or falling off the roof into a snowbank don’t sound like viable options to me. My attic’s fairly well insulated, so I guess the snow might offer the side benefit of actually acting like additional insulation during the bitter cold we’ll be experiencing during the next few days.
I’m in Northwest Ohio, and it’s still snowing like a mother here. Thanks for the new thing to worry about, Guy! Luckily (?), my bf and I have had the puking flu for two days (It’s spared my 12 year old daughter, so far: the poor little dear has gotten meals, etc., for herself all this time) so we haven’t had the energy to even look outside. Now that I’m pretty well recovering, I wish I hadn’t looked.
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I beg to differ. A large accumluation of snow can be extremely heavy, more so if it’s particularly wet. Buildings in my area are typically designed to take into account snow loads for 50 year storms (a storm so big that the probability of it occuring is once every 50 years). Engineers here typically design for snow loads of 38.5 lbs per square foot.
I don’t know the snow loadings for your area, but as long as your house was built to local building codes, you shouldn’t have anything to worry about.
You may be right on this, but I’ve heard media experts and not a few insurance companies over the years remind people that removing deep snow from their roofs might be a good idea–providing they didn’t slip off the roof and break their necks.
I’ve also seen Associated Press photos of northerners shoveling snow off their roofs, during 4-foot snowstorms–and that’s a tradition that goes back a couple of generations. You’d think if it weren’t necessary, some university professor of engineering would tell people they’re wasting their time and word would go out to the public at large.
I’ve seen awnings go down and shed roofs collapse under two feet of unusually **wet ** snow.
Generally, snowfall in amounts over a foot tend to be dry. 10" of wet snow could weigh substantially more than 18" of powdery snow. If it is cold, and the snow is dry, you don’t have much to worry about.
The Philadelphia area took on 33" of snow a few years ago, and the previous record was 22". Some flat roofed structures or shallow pitched structures (sheds, warehouses) had issues, but even older homes and flat roofed city homes (row homes) had no issues.
Snow is heavy…but on a sq. foot by foot basis, it really isn’t much.
I acually heard, then watched a roof collape on an old mill that was probably 150 years old. I was about 200 feet away and it was quite a sight. Not a lot of snow but very wet with a lot of ice also. I think it was just time for it to go. BTW it was empty and no one was hurt.
“It is not the depth, but the weight of accumulated snow/ice moisture content that is critical in assessing your roof’s vulnerability. Water content of snow may range from 3% for a very dry snow to 20% for compacted snow to nearly 100% for ice. Water per inch of depth weighs 5.2 pounds per square foot. Thus, a modern roof designed to carry a snow load of 40 pounds per horizontal square foot is designed to support an equivalent of approximately 3’ 6” of compacted snow. "
After I first moved to Vermont, there was a major blizzard on January 7 - 8, 1996. Many roofs collapsed on houses, businesses, public buildings, covered bridges and other structures. That amount and type of snow is not typical most places, but it can bring down buildings even in areas that have structures built to handle “normal” yearly accumulations.
Well, removing really deep snow is a good idea, but for the average heavy snowfall, it’s not really necessary. Also, the danger of injury is much greater than the danger of a roof collapse. Keep in mind, Guy is worried about a possible 20" accumulation which is well below the margin of safety.
A professor of engineering would tell people that a properly designed and constructed building will withstand the snow loads they were designed for as dictated by local building codes. A 4 ft accumulation can definitely be a cause for concern especially for buildings not built to code or kept in poor repair.
The bigger problem is usually the ice formation due to a poorly insulated attic. Glaciation occurs when the snow in contact with the roof melts, then freezes, causing damming to occur up past the ice shield. When the next melting occurs, water gets in under the ice shield, into your crawl space and then into your walls, ending up on your carpet. Trust me on this. We vacuumed out a couple of gallons last winter after a particularly heavy accumulation.
The fix is to have someone check your attic for adequate insulation. If the house was built in the 70s or 80s, it was likely not not correctly. It’s an easy fix to have additional insulation blown in.
Well, it looks like we probably got the 20" of snow that they were estimating, but luckily it looks like a lot of it blew off the roof. Unfortunately, the damned stuff drifted into areas where I ended up having to shovel it off of the sidewalk. Now I’ve got a strained muscle in my left arm and a sore back to go along with my low-grade fever. I guess I’m lucky that I haven’t gotten the puking-type flu that ggurl mentioned, so all’s well in the world.
Well, my sympathies to anyone digging out from under this winter storm. Hopefully you won’t get the subzero temps we’re suposed to be getting the next couple of days.
It never snows on the Isle of Man, does it? Several meters of snow would probably collapse the majority of roofs. One thing to be concerned about is the possibility of a rain storm after the snow – wet heavy snow is a recipe for disaster.
They actually manufacture snow rakes – essentially rakes on very long poles – specifically for the purpose of removing snow from roofs.
Luckily (?), my bf and I have had the puking flu for two days (It’s spared my 12 year old daughter, so far: the poor little dear has gotten meals, etc., for herself all this time) so we haven’t had the energy to even look outside. Now that I’m pretty well recovering, I wish I hadn’t looked.