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I very much hope this is what happens in the next few days. I just don't see any realistic way to clear snow off the roof without climbing up there, and that's not happening.Quote:
Originally Posted by old goat
I'm not concerned about flooding at my house, though I do live adjacent to Dry Creek on the map - and remember you commenting on that before... The Dry Creek near me is down in a gully, plenty deep, plenty of downstream dispersal area away from my house.
My wife and I cleared our roof one time but those days are long over. We did use safety rope although when we were done we didn't need the ladder to get off the roof. This was in the early 90's (not the same year as the flooding) and the snow was deeper on the ground than it is now. But winter isn't over.
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For peace of mind and guesstimating purposes, IIRC, blower snow is around 10%. Wet snow around 20-25%. Ice would be just under 100%. I would guess you are currently less than 50% of live load design minimum.Quote:
Originally Posted by El Chupacabra
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Thanks - one way or another, I'm going to find out in a couple of days here.Quote:
Originally Posted by Alpinord
Looking around the neighborhood, almost no houses have any signs of snow removal from the roof tops (in the sense of being raked or shoveled). And the local Nextdoor has no posts concerned about snow load, only about ice dams - which is surprising given how much bitching there is about anything and everything on there.
It seems like almost all the new construction in Tahoe has flat roofs now. What’s up with that? Is it somehow easier to build to hold the snow than to shed it?
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Roof load is calculated independent of pitch, so it has to be just as strong at 8/12 as it does when flat. Even metal won't reliably shed below about 8/12, so the engineering assumes no shedding at all.
I have a pic of one of my guys with a snowblower inside of a living room a few years ago, and I fully expect we'll be able to refresh that photo in a couple of weeks.
I've shoveled my whole roof twice this winter. El Chup, fingers crossed for you but I would not be a bit surprised if you had an... incident. That shit is heavier than you think and the rain will really rapidly add to the load.
I don’t know if it’s local, but this isn’t correct for OR anywayQuote:
Originally Posted by climberevan
Huh. That was how it was explained to me by engineers in CO and Tahoe. I have to build it like they specify.Quote:
Originally Posted by ::: :::
But certainly it's true that low to mid pitch roofs don't shed snow anyway.
I'm no engineer so feel free to correct or ignore me, but my understanding--having pulled a bunch of permits here involving roofs and engineers, is that the snow load in psf is the same regardless of pitch but the size of the rafters to support said load varies with pitch.
Here there is a percentage reduction based on pitch.
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My house roof has never slid snow, though seems steep ish - 8/12 maybe? Heavy concrete tile, not light weight - roofer from last summer who did some repairs said it's the older style you don't have to be as careful about as far as where you walk on it.
Just walked around the house looking closely at the ceiling, windows, and door jambs. There's some hairline cracking along drywall seams, but only in straight lines where the drywall pieces come together). Some of those cracks were already there, not sure if there are any new ones. No doors are sticking.
I'm not sure what it is locally but my neighbors just had an interesting problem this winter. They've got a steep pitched garage roof that slides multiple times every winter. Last summer they installed solar panels which provided enough anchoring that the roof stopped shedding. After a large amount of snow early this winter they had multiple cracked trusses and rafters and were quite lucky to not have lost the entire structure and the cars/gear inside.Quote:
Originally Posted by old goat
Based upon this it seems like it would make more sense to require roof loads to be more standardized due to the uncertainty of what future landowners may do.
Like I said I'm not familiar with the local code requirements but it was an eye-opening issue to me that I'd never thought of.
I don't know where you are but it certainly seems weird that the roof woudn't be engineered for the snow load on a non-siding roof.
Around here some roofs aren't sliding because the snow on the ground is up to the roof.
I'm on the east side of the Cascades in Washington. We get enough snow that homes need to be built to 80 lbf. The garage very well could have not been built to code, but the structure is about 20 years old and large enough that it should have been permitted.Quote:
Originally Posted by old goat
I was more commenting about how allowing lower snowload on sliding roofs could have issues later in time.
Oh shit. Hang-fire.Quote:
Originally Posted by ticketchecker
I was kind of cranky that I had to shovel plow berms from our 150 feet of sidewalk a few times this winter, but after reading this thread I'm counting my blessings.
She slid out about two more feet over the last couple days and finally lest loose tonight.Quote:
Originally Posted by riser4
Now I can let the dog out alone again
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I get the ice overhang too. This was last year, its bigger and thicker this year.
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FWIW and to follow up on the above ‘chairlift comment’…..Quote:
Originally Posted by Alpinord
-over a 6:12 pitch local codes may or may not allow a percentage reduction in live/snow loads. If involved, the architect/designer &/or engineer may decide to not take the reduction and even bump the loading &/or deflection criteria for the structural design. For ‘value engineering’, for instance, a truss engineer could simply meet the minimums, take the reduction and be legal. Accumulative loads (valleys, dumping onto lower roofs, etc) would need to be part of the engineering.
-the trend here for higher end projects, is to not take the allowed reduction, possibly bumping the live load and stiffen the deflection.
-for longer spans (horizontal distance between bearing), allowable deflections for both rafters and trusses (same for floor joists) could deflect ceilings noticeably when loaded. To minimize this, a stiffer deflection value could (and should) be used. This in turn might beef up the roof system relative to live load capacity.
-for the same span and different roof pitches, the rafters will have different lengths. To meet loading, span and deflection criteria, the rafter sizing, design series or layout may or may not need to be different. Part of the dead loading is the weight of the roofing material and is added to the live (snow) load to determine total design load.
-in a County where we range from 30ish to 150ish or more snow loading, a dual ‘zone’ system has been the basis for design load formulas based on elevation. Now the GIS system is incorporating more variably criteria within the same zone and elevation to account for more location specific data.
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Is it a bad sign when your ice dams are forming tiers?
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There must be heat coming out from under that edge.
That’s over an unheated garage, and north facing. That roof section does extend over part of the living space though, so the attic space is getting heat from that.Quote:
Originally Posted by ötzi
Hoping with the snow cleared and warmer weather coming that they’ll loosen up and shed.
No ice dams, but our garage roof was not subject to any snowload code. The side door had become hard to open/close. 6” of rain expected between tomorrow and Sunday. Hopefully this does the trick. Also spent the afternoon restoring drainage systems around the house.
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Less snow on the roof of the house… I guess our insulation isn’t that great.
My friend went up to his a-frame in bear valley. Shoveling was futile. The bear valley village has now recorded over 600”, which I think is more than the ski hill over the ridge.
^^^Here tooQuote:
Originally Posted by Alpinord
I have a cabin project in Govy that has a snow load of something like 320#/sf. [need to dbl-check that with the eng, but that’s what I’m remembering atm]
Hm. Well something is melting that down and making those icicles, I dunno.Quote:
Originally Posted by J. Barron DeJong
They did add dead load to the trusses that changed the design criteria. As noted by others, the code would have required the roof design to hold the snow load without snow sliding off. Does this roof shed one direction or two? If two, it sounds like possibly a differential loading situation compounded the loading on the panels side.Quote:
Originally Posted by John_B
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Teflon-coated roofing shingles. We'll be rich!
Did you pump up a raft with survival gear? 6” of rain![emoji15]Quote:
Originally Posted by bodywhomper
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It's single pitch. Maybe 7/12 or 8/12. I don't have a good eye for that.Quote:
Originally Posted by Alpinord
A 7:12 is ~30 deg if you have a clinometer.
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Gonna design a bunker? [emoji6]Quote:
Originally Posted by ::: :::
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It's my neighbors garage so I'll likely leave it as an unknown mystery. 30 degrees sounds about right.Quote:
Originally Posted by Alpinord
Main gable is 15:12Quote:
Originally Posted by Alpinord
FTR, Comparing notes with a colleague on this season’s unique conditions, including unprecedented ice damming at multiple elevations:Quote:
Originally Posted by Alpinord
-snow started coming just after Christmas and the storms came back to back to back.
-around the 2nd of January, a high moisture storm hit (like last year) which created power line issues, outages and fluctuations. It laid down a saturated layer of snow, which then froze quickly and got buried in the same storm as the temps dropped. Another cold storm came on it’s heels, along with others.
-the temps stayed cold which was great for snow quality, but not so much for the frozen layer on the roofs and eaves.
-a warming, dry spell melted snow which in turn added to the ice layer and dams (see layer in snow cut)
-more snow came with return to colder temps and kept the snow quality without much of a melt which had been generally happening over many years. Again, it’s more like it was 20 plus years ago than the last couple decades.
-some recent melts in the last couple weeks, including now and the pending warm storm, have gotten the water moving again and refreezing.
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Ha! It’s gonna be an interesting storm. In the past 2 days several relatively modern structures in a large strip mall in town have failed. Seems like bad structural design or the contractor didn’t build to design and inspections didn’t catch it. Pretty big bummer. Included a bank and med clinic.Quote:
Originally Posted by Alpinord
In some areas of CA, code includes snow load with EQ. Example, “A minimum of twenty percent (20%) of the design snow load (Pf) shall be added to the dead load for seismic design.” https://www.townofmammothlakes.ca.go...ds-2020?bidId=
I’m guessing even new structures in places like mammoth lakes and Tahoe are outside of design capacity.
I’d check your insurance policy and make sure you won’t be excluded if you have a collapse for not taking reasonable steps to prevent it.Quote:
Originally Posted by El Chupacabra
Our ground snow load is 315. We're designed for 400. Except the deck. Our deck beams are up to 17 ft 4x8 on 2' centers, many of them supported in pocket holes in the T111 siding without any framing. Years ago, tired of shoveling I hung a plumb line from the center of a long beam ending 1/4 in above a rock. Figured I'd shovel if the the bob touched the stone. It never did. The deck has been reinforced since then. This winter I've shoveled a total of 8 feet of snow off the deck to keep the snow at the deck rails (42 in) because I like to look out the front windows.
Our direct vents are required to be 12 feet above grade. Stll have 4 feet showing since they're undere a 2 foot over hang.
To the builders and architects who work in Tahoe and other crazy snowy areas, what is your ideal trouble free house? A 2 story, with a roof that is just two steep surfaces, no valleys and a 12 pitch with metal roofing and all vents going through the siding in the attic? Basically the house a kid draws?
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My friend’s place in bear valley. Photo from yesterday. It’s two stories on the side of the photo and three stories on the other side. There’s a dormer on the top story that’s been a problem when there was 10’ less depth of snow. He skied onto the roof and cleared the vents. He can’t close any interior doors.
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