Hi all,
Running into a problem where snow slides off metal roof onto neighbour’s driveway, which is illegal here. The roof is corrugated metal, 12:12. It already has snow stops installed about every 6 ft. These are v-shaped, bent sheet metal, screwed to the roof metal. Recent storm snow, about a foot, and warm temps allowed snow to slide off, landing on neibor’s driveway about 8 ft from building. The only thing that occurs to me is more snow stops, but I’ve been talking to a few local roofers, etc., and they seem to feel that once the snow builds up to the height of the snow stops, it will likely slide anyway.
Any ideas, besides installing asphalt roofing, (a bit late for that)?
Any ideas apprecieated, thanks.
Replies
Is this a new house or a new roof? What happened last winter?
John
It is a new house.
you should put a roof over that...
k
It already has snow stops installed about every 6 ft.
That's almost like not having any at all.
They should be installed 18"-24" apart per row with the second row staggered half way between the 1st row. Steeper roofs require more rows.
The guys saying that the guards only hold their depth of snow don't understand how they work.
http://www.quittintime.com/ View Image
KY, what the heck would you know about snow. Seriously, thanks for the input. I am talking about snow country, Rocky Mtns/Columia Mtns. We get avg over 6 ft of snow, 6 months of winter. Are you talking about the same "snow stops", bent out of sheet metal? Thanks for weighing in.
KY, what the heck would you know about snow.
Obviously more than the roofers you've been talking to. Seems like you've got two choices: Keep it on the roof or let it slide.
Are you talking about the same "snow stops", bent out of sheet metal?
There are numerous designs, but the function is the same: Keep the snow on the roof 'til it comes off as water or drifts off in flakes.
Can your roof support 6' of snow? Is the roof insulated so well that it won't constantly melt from the bottom?
http://www.traditional-building.com/article/snowg.htm
http://www.siegersnowguards.com/c1b2.gif
http://www.quittintime.com/ View Image
Yes, you do obviosly know more that these roofers. Do you deal with snow in KY?
I am located in the mountains of BC, Canada. Our roof snow load is calculated to be about 50psf. Yes, the house plans are reviewed by a PEng for structural. Some simple houses are designed using span tables, etc. from the code book, but this is a very complecated roof, with dormers, etc. which probably would work great in S. Texas.
We just had our first significant snowfall, about a foot over 2-3 days. There are icicles and ice dams forming already.
Thanks to all for the great info. Any more ideas will be v. welcome.
Do you deal with snow in KY?
Yeah - not near as much as you, but we can get 2' - 3' at a time on occasion. Doesn't happen often and in recent years we've hardly gotten more than 5"-6" at once and that all melts before it snows again. http://www.quittintime.com/ View Image
Our roof snow load is calculated to be about 50psf.
That sounds light, particularly if you're trying to keep the snow on the roof.
The formula for calculating roof snow load is 0.7 times the ground snow load times a roof slope factor, which would be 0.4 for a 12:12 slippery unobstructed roof and 0.7 for all other roofs (e.g. metal with snow stops).
We just had our first significant snowfall, about a foot over 2-3 days. There are icicles and ice dams forming
Then you've got another problem: excess heat loss to the roof and inadequate roof ventilation. You can't keep the snow on the roof if it's melting at the base. Increase the attic insulation, seal all penetrations from the conditioned space and ventilate the roof.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Welcome Back.http://www.quittintime.com/ View Image
Another word of caution about the snow stops.
Two winters ago here in Driggs, ID, Ace Hardware built a new building with a pent metal roof along the front of their building. The first year was annoying that every snowstorm slid off the metal and onto the sidewalk/front of cars. So they installed some heavy duty snow stops. Last winter comes along and they thought everything was going great since the snow stayed up on the roof, and got bigger and bigger and... until one day the "cornice" broke free over the snowstops and several thousand pounds of snowdrift landed on the hoods/windshields of about 6 cars. Luckily no one was injured as it went through windshields and totaled all the cars.
So this year they poured another seven feet of sidewalk/curb farther out from the building and have permently posted no parking signs around the building year round. The insurance bill from that snowdrift must have been about the size of the built up snowdrift from the snowstops.
Lesson to be learned here is the owner will have keep an eye on the snow and rake it off as needed.
I can understand the neighbors concern and his obvious right to feel he can use his own driveway safely. This problem should have been addressed/thought of before a footing was poured. From the pics it looks like their was ample room to move the building over a few feet.
We do it a bit differently here.
S = CB * SS +SR
CB = 0.45 for roofs less than 4.3 M wide, 0.55 for wider roofs.
SS = 3.7 kPA, SR = 0.2 kPA (1/50) (from climate data for location)
SS is ground snowload, SR is a rain factor.
S = 2.24 kPa which is abour 47 psf
Your formula for non slippery roof woule give 3.7 * 0.7 * 0.7 = 1.8 kPA
Sorry about the metric. Don't have conversion of kPa to psf handy.
Edited 12/20/2008 10:44 am ET by Blaeberry
Dumb question time.........snow sliding off a roof to a neighboring driveway is illegal?
Whose bright idea? The locals, I asume, have allowed building permits with specified set backs and design approvals.
You're supposed to stack it until it melts?
Sorry for being ignorant of the facts but it just doesn't make any sense to me. What city are you in?
...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...Be kind to your children....they will choose your nursing home....aim low boys, they're ridin' shetland ponies !!
I'm in Golden BC, Canada. I'm trying research the legal end of it, I'm not sure if it is code, or a municipal bylaw. I think it says that all storm water is to be kept off neighbor's property. Will send more detail as soon as I find it.
Thanks to all.
Whether it's the law or not, unleashing avalanches into your neighbor's driveway wouldn't be too neighborly.Pete
You could frame a false gable on the offending roof slope to redirect the snow slides. That would be pretty extreme. But it would work if things get real bad between you and the neighbor.
I have only made one prayer to God - A very short one: "O Lord, make my enemies ridiculous". And God granted it. [Voltaire]
Good to here from you!You get out of life what you put into it......minus taxes.
Marv
There is already a shed dormer. Will try to post a pic or 2 tomorrow AM.
Hi all, finally posting photos. Sorry about the delay.
The property line is about where the spruce tree is.
Better view of property line, approx. at the Spruce Tree.
from that picture, it looks like you have a full run of stops...or is the problem with six foot spacing only on the shed roof portion?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
It actually looks like I was wrong. There is only one snow stop, near the bottom edge of the roof. I was thinking that there were several of them, further up the roof. They do run the full width of each roof area.
These are bent from sheet metal, about 4" tall. The top edge is approx. 90 degrees to the roof, and the botttom is approx. 45 degrees. They are screwed to the ribs of the roofing metal with rubber gasketed screws (#14 Farm screws around here).
Perhaps adding a few more rows of these stops would solve the problem? I wonder how close together they shoud be?
Thanks to all for the v. helpful info.
I don't have too much faith in them just screwed to the high spots on the sheet metal. might only last a couple years before the load tears the sheet metal and rips holes where the screws were. This sounds liek a DIY idea, not a well tested method.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
These sheet metal snow stops are pretty common around here. I have used them quite often on 4:12 roofs, but not on 12:12.
You may well be right about the screw tearing out after a few years. I suppose if you put the stops every foot it would kind of spread the load over a lot more screws.
I am going to send the owner a link to the alpine snowstops layout calculator on Mon. I think that would be the best idea. They ask for details on snow and rain, and detailed dimensions for each part of the roof. This one is v. complicated, with numerous dormers. It even has skylights, which will almost certainly leak eventually.
Thanks again.
We did a very large metal roof 10/12, 24' from eve to ridge, looked good ....then put snow stops on. Clear plastic type screwed to the strapping spaced like Piffin said. You need to silly cone each one. The good part of putting many on is you have backing and the strapping will hold in the area of each stop. If you use one big one near the eve, whats going to keep there. That puppy would need to be lagged to some good pre planned backing. Also what you do on that side of your roof you need to do the other or you may over load one side, 3' of dry snow still adds up in lbs.
Or stay on the ground, buy small cat, and clean it up.
Oh, the snow does stay on the big roof
Based on that picture, I think the advice you got about snow stops was the best.
Experience is a hard teacher - It gives you the test first, then the lesson.
With that type of situation you may need a pipe rail system just in from the eaves.
I think http://www.alpinesnowguards .com might be able to provide what you need.
Your link didn't work:
http://www.alpinesnowguards.com/pipe-snowguards.php
I was hoping you'd chime in.http://www.quittintime.com/ View Image
Grant,
Thanks for fixing that link.
I know and you know that if you stop the slide at the roof surface it will be retained , but sometimes I like the pipe system for larger roof areas and very tall roofs.
Sieger Model C is definately my hands down favorite for individual guards however.
Walter
build a higher fence between the driveway and the roof
This could be the only option. I'm not sure how one could ever be 100% certain that a layer of snow above the snow stops would not avalanche. It would need to be a very strong fence, probably concrete.
I will post some pics when I get home, in about an hour, I think.
http://www.alpinesnowguards.com/snowguard-faq.php#height-snow-guard
I like the pipe system for larger roof areas and very tall roofs.
I've seen the rails in NE and Canada, but there's none around here. I've probably only done snow guards on about 10 buildings and that was usually after the waste vents or gutters got ripped off.http://www.quittintime.com/ View Image
heres one I put up about 10 years ago after rebuilding the eaves and putting on these galv. panels.
I do a lot of snow retention here - got about 20 C's to install Sat. on a small slate job.
Ignore that 2 MB file --I'm posting from a laptop from the front seat of the truck.
View Image
View Image
I just had to have all the valley roofing repaired on our Colorado house because of snow/ice slides last winter. The snow/ice on one side of the valley crashed down onto the opposite valley and crushed the SIPs underneath.
Our repair approach was to repair/replace the standing seam roofing and then install cast alluminum cloverleaf shaped snow guards high in the valley. Placed them at 24" spacing, staggered one above the other. Set them only in the valleys as we don't care (actually encourage) if the rest slides.
Will report in the spring if it works.
Stef
I neglected to mention that Slateman put me on to these devices.
Edited 12/11/2008 1:45 pm ET by fatboy2
What are cast aluminum cloverleafs, please. We may need them.
It is a style. All these devices have different looks to them. some acrilic plastic see through, some plain metal angles, some the cast with a design. The cloverleave retains snow but makes it easy for water to run by and doesn't retain leave debris the way plain angle ice block do, and looks nicer.But I came to this discussion late before seeing all the info. Walter ( slateman) has given the best in his links and pictures to the rail system for what I think you would need. And don't use Piffin screws to attach it to the roof with LOL
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Company called Alpine Snow Stops. Google snow stops and you'll find a zillion of them
S
Well, if it's illegal for a driveway to be covered by snow falling off a roof I can only suggest you use the weight of the law to have the driveway removed.
Runnerguy
I think it is okay to run the driveway along the property line but not okay to dump snow in your neibors"s yard.
Edited 12/14/2008 12:26 pm ET by Blaeberry
I know. I said it as a joke.
Seriously, I don't understand how an ordanance would include stormwater. For example, many lots slope side to side with an "uphill" neighbor and a "downhill" neighbor. There's no way water can't be kept from flowing from one yard to another. And further, some of those lots slope also to the rear with another "downhill" lot located there.
Runnerguy
Generally a municipality would let the lay of the land be the boss or guide to how storm water should flow. What would be controlled is a homeowner back filling yard as to send water on to the joining property.
Or building an in ground pool and raising the yard considerably to make your water become the problem of the adjoining property owner.
Not saying these type of things can't be done, but the water run off has to be addressed at the same time. Bottom line is, not to create a problem for the adjoining property owner by you actions.
The snow went 8 ft. to the side? That's pretty far. I think a stout fence on the border is called for.
The very advantage of metal roofs is that snow will slide off, rather than accumulate. Around here, we tend to have steeper roofs. We also don't use 'snow stoppers,' rather relying on 'snow splitters.' These down-opening "Vee's" are intended to break the sliding slab of snow into a gentler powdery fall (not that you'd want to be under it when it fell). When I've seen these slabe break free, the snow has piled itself quite nearly, almost next to the building.
"Snow splitters" are also placed just uphill from each roof penetration, to prevent a slab from hitting them.
They come in various designs, some people even collect the antique roof stops for snow. Up in NH there were buildings 200 years old where these were still working very well to prevent slides, now huge icicles are another matter........but they usually just drop next to the house and come flying through a window when they deflect off the piled up snow...:-)
Icicles are not huge, as yet. And as you say, they mostly go straight down, when they fall. The snow is the thing. Want to keep it on the roof.
Thanks for the info, definitely would like more details on these.
One every six feet is kind of laughable - like trying to win the Daytona 500 with a MoPed instead of a Mopar
One every foot in a stagered pattern comes closer, but if you are in a really high snow area, you might need the kind of system that suspends a rail or pipe or two along a few inches above the roof.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Thanks, Piffin, What the heck are Piffin Screws anyway. What do you mean about staggering. I'm thinking the snow stops would run full length.
Thanks for the info.
staggering them means one up and the next down a foot or so alternating every other one evenly across the roof.A piffin screw is a screw used inappropriately. I have found several times in remodeling that cabinets have been installed with sheet rock screws which are weak and brittle, so they break just at the shoulder to shank. A heavier gauge screw with better metal is easy to find for structural work like that, but there are still fools out there who try to use SR screws even for things like building scaffolding or attaching ledger boards for decks. I rail against such improper use when it creates a danger type situation, so the guys here got to kidding me and added piffinscrew to the builder's lexicon, generally meaning a sheetrock screw used for heavier work.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks for the no BS explanation. I have been wondering for years!
You can use a roof snow rake to pull it off when you want to. Then shovel it off.
Is this your house? Might an apology and a nice bottle of scotch and a promise to shovel off the snow from your roof as soon a humanly possible be a possibility?
You build as best you can,, you have snowstops,, some winters have more snow than others,, and if it needs to shed,, it needs to shed! You don't want a pile of snow up there with mid season rains on it,, complications inside! I almost prefer a steel roof without snowstops. Why delay the eventual? (snow stops at entry and high traffic for sure!)
my 2 cents,
d
No, not my house.
The two neighbours are not likely to be able to solve the problem through through better human relations, in my opinion. The guy with the driveway problem thinks his grandchildren need to be safe, and of course may want to park on the driveway. I guess it is his right.
The guy with the roof says he is willing to do whatever is needed to keep the snow on the roof. I'm not sure that there will ever be certainty that the snow will stay there. Maybe a combination of snow stops and a huge wall??
I have wondered if there is any way to deflect the snow downward as it comes off the edge of the roof? Someone ( foret the name) suggested v-shaped splitters at eaves to break up the slabs and slow them down.
Thanks to all for the ideas.
Edited 12/15/2008 5:06 pm ET by Blaeberry
This is what I used on our house: http://snoblox-snojax.com/I'm in Colorado and it can snow substantially here.This outfit also will calculate the spacing pattern for you.
Thanks, this looks like a good option. I am going to send a link to this discussion to the two owners (who are both carpenters).
You're welcome.Mine have been up for five years. No problems and no snow slides.
I'll weigh in here, with hindsight, you've got a few problems with the design, building location etc. With lots of snow stops you will keep the majority of the snow on the roof, but will have the ice damn issue to deal with, ice is already present, and the drip in the spring. As mentioned before the snow stops will have to be bomber. I live and build in snow country, and the prior thought of where the snow needs to go is often ignored by the designers/arcy's . We'll have 5 feet of it on the ground and the roofs before too long. At this point you might be better off getting a variance from the neighbor to build a carpot off that side of the house to catch and hold the snow so that it doesn't bury some one or something. The carport could end at the property line, or extend over it. If there are kids around who aren't snow smart, then a rope line should be set up so they don't play in the drop zone. If the roof lets go after any signifacant snow fall someone caught in the aftermath probably wont get a second chance, unless the help is watching it happen and they have a good shovel and an even stronger back!
If you are just the builder, I would CYA with homeowner and neighbor for any future damage/injury.
Good luck
Rob
Looking at the problem thru the lens of snow science, I think you want no snow stops. The snow stops are allowing a greater depth of snow to accumulate, and physics shows that the snow mass will shear it self up and over the stops. Without any stops, the smooth and steep metal surface will shed many small avalanches which hopefully will not travel as far as the less frequent larger avalanches you have now.
Another issue: As you can see in the photos, there are 2 doors near the rear of the building, access is via the walkway under the roofs we are concerned about. On door is the entry to a separate suite, located upstairs. This would be the only exit except for the bedroom window, which meets usual requirements to be useable as an exit in case of a fire.
Edited 12/16/2008 2:44 pm ET by Blaeberry
Thats the kind of advice which might get someone badly hurt.
Because the doors and driveway are sited without regard to the snow issues is preciely why it's imperative that a good system is designed to retain the snow.
Why is there one in every crowd?
You can lead a horse to water but...
Thanks for posting excellent solutions you can be sure at least one person will putting them to good use.
Thank you.
get a room
What is snow science telling you about this case? I am getting conflicting advice, some seem certain that the snow can be retained on the roof, some (like you) do not. The situation is a bit different than the typical avalanche hazard, because it is not on the ground, it is on a roof. I am not aware of much science re. roof avalanches.
There is no science that I am aware of regarding snow avalanches off roofs, I was trying to extrapolate what I know of mountain avalanches, snow dynamics, geology, and 27 years in the building industry. I believe you were correct in fearing that in a deep snowfall, that the snow pack above the guards would fail. It is well established that a 45 degree slope is a perfect avalanche angle. Snow behaves the same wether it is on a roof, or on a mountain. My point is without the guards, you will have many minor releases, and you will not accumulate snow on the roof. At present, you have a system where the existing snow stops are allowing a bigger load to accumulate, and then this shears above and over the stops. I think you would do well to consider not allowing the snow to accumulate, and snow will not accumulate on a 45 degree heated metal surface. You may have to construct a gable shed in front of the door.
People like slateman are allowed to dogmatically disagree with me to their hearts content
I appreciate your input. I too am well aware of the basics of normal mountain avalanches, and of roof avalanches. I am really torn on this issue. My own house has a 12:12 metal roof, and gable dormers. The snow really hangs up in the valleys under certain conditions. Often it will sag into the valleys, but not release, and I can get about 4 ft of snow in the valleys. They come off big when they do release. Fortunately we are not forced to walk under the valleys, and the debris cones mark the locations of the deposition areas.
I am envisioning a scenario where someone walks out, slams the door and takes about 2 steps. Wham! If there is a retaining wall tall eneough to keep the snow off the neighbour's driveway, the terrain trap potential is huge.
Even with no snow stops, the avalanches could be big eneough to hurt someone. With snow stops, they might not happen at all?? Or they might be v. large. What to do?
Slateman seem confident that the snow can actually be retained on the roof, which would definitely solve the most serious problem.
From the legal end, I finally have some answers.
There is a covenant attached to the land which requires the owner to have a geotech P.Eng prepare an assessment to adress the requirements for drainage procedures and installations to ensure that drainage from the land will not damage or disrupt adjacent lands.
Also the Subdivision Development Bylaw states:
Site runoff shall not flow onto adjacent properties.
Thanks to all for the excellent discussion over tha last few days.
Well then, maybe what you do need are several parallel, stout, and tall pipe type snow stops. Buy even the pipe-types have small avalanches. I have seen the snow slowly deform around and thru the pipes, and then fall off, but the pieces that do are small.
I believe that you are in interior BC, am I right about this?
We have similar rules here - runoff is not supposed to go into the neighbor's yard. I'm not a builder, but it looks like this problem was waiting to happen with the siting of the house and design of the roof.
To my inexperienced eye that just plain looks dangerous - the snow could let go at any moment and crush people under. The problem is that you might keep the snow up there with stops, but what if you get 6 feet accumulation (not unusual in Utah and we are at a much lower latitude) and then it lets go? I defer to the experts, but I'd consider removing all the stops and building a super reinforced roof over the walkway to protect people there and a reinforced concrete fence to keep the snow in the yard.
Those icicles after just a little snow like that look ominous - are you sure the insulation and venting on that roof is sufficient?
Would it be possible to wrap that deck around on that side? The snow would fall on the deck, they shovel it off, or shoot it off with a smaller snowblower, and you end up with a "somewhat" covered walkway beneath.
How do you get along with your neighbor?
could the matter be resolved by shoveling his driveway for him? or some other such solution?
Be an interesting court arguement.. how do you prove that a particular flake originated from your roof? what identify feature establishes it as "yours"?
" could the matter be resolved by shoveling his driveway for him? or some other such solution? "
Frenchy,
What if the neighbor's kids are pulling each other along the driveway on snow shovels when the roof lets go on top of them?
Since I don't know how much or how hard the snow would be the results could be a lot of fun and giggles. I'd suspect that snow wouldn't be too densely packed on a metal roof and unless it's a really massive roof close to the ground unlikely to cause any real damage.. (pure speculation) kids pulling each other along in the snow might not object to the occasional heavy snow fall. In fact it might be seen as a lot of fun..
I've been under big pine trees when they let go and got a really good laugh. Once going down a steep hill riding a toboggan a pine tree reacting to my hollering, let go just before I arrived and managed to launch me into the air.. Now I claimed to have gone a mile high but my friends assured me it was closer to six feet, still it sure was fun!
I have used such metal roof snow guards and they work perfectly on my house. And I am living in the snowy region. Maybe they can help you.