Snow Load & Roof Clearing

[garyl62]

In John's journal today (2.21.16) and other times in the past, there are often comments about shoveling the roof. I know this is a common practice and in many cases I'm sure it saves a building from collapse. My question is not related to older buildings that were not built to today's standards, but rather new buildings that have met all current codes. With the State of Michigan dictating a snow load rating and truss manufacturers factoring snow load into their engineering calculations, why is it that people still continue to shovel snow off the roofs of buildings that were built to withstand the snow load generated in snowbelt area's such as the Keweenaw?

I've thought about the day that I'm able to build a place of my own up in that area and I often wonder if it's built to withhold the snow load, has a 8/12 or higher pitch, would I still end up having to find someone to clear it once or twice a season? Not taking anything away from any of you that do that, I'm just not understanding why it seems even people who have new homes continue to do this.

Hoping someone can provide some logic to me as it seems like a lot of work that isn't really necessary.

 

[mrbb]

my guess would be this, snow load, YES< but as that DEEP snow starts to melt and turn into WET heavy snow, and water, then back and forth ICE, that freezing and thawing can pull the roof screws out or, make water get under shingles and then LEAKS

heavy snow is never a good idea on a roof, IF you can get it off!

 

[Woodtic]

MRBB is right on the freeze thaw. Snow load on a pole building in Houghton county is 80lb a sq ft. In Il it's 40lb. Some roofs have a harder time shedding and have to cleared. I have never had to clear my roofs in the UP but I have had to get them started with a roof rake.

 

[mrbb]

that's right don't forget about direction of the building in relation to the sun
seen many buildings here where one side of roof gets almost NO sun at all, and can hold snow for weeks past other side being DRY of it!!
so, on a roof like that, its pretty easy for one side to get excessive amounts of snow load!

 

[snowchief]

I shovel mine to prevent Ice dams

 

[timo]

if i was able too I would just do it for a peace of mind.

 

[ezra]

U also have to think about things like plumbing vent placement etc.
look on the inside wall of a snowbelt home with steel roof . if vent is on ext wall close to bottom there will often be poped drywall or paneling where pvc was bent over flexed in the wall and messed up wall when load slid off.
also plan driveway and walks accordingly have seen some trucks that took the brunt of a 12foot drop of 6 in thick ice covered in 10 in of snow . that chit could kill some one

 

[Admin]

Those were all awesome answers. My answer, for my case is: The load rating of my trusses is 90 lbs/ft[SUP]2[/SUP]. I really do not know how much snow that is, plus the snow load will be different for different areas (valleys have more, peaks less, wet snow more, dry less). So it is really for peace of mind.

If you did an 8/12, metal roof, with no dormers or valleys, then you would not have to worry about it at all. The shop is 4/12 and clears all on its own. Just do what Ezra says and pay attention to what you have in your drop zones!

-John

 

[yamadooed]

I've an 8/12 and the PO stated they never shoveled or raked... What little damage I noticed was some shingle tear in multiple spots on a relatively new shingled roof...

 

[snobuilder]

I've an 8/12 and the PO stated they never shoveled or raked... What little damage I noticed was some shingle tear in multiple spots on a relatively new shingled roof...

Those are rake/shovel marks.

 

[yamadooed]

Those are rake/shovel marks.

I only use anti chaffing rakes Mr Snobisket...

 

[skeeter2010]

We were up a few weeks ago after the 50" snow week and people had been clearing roofs. As I watched people shovel off the steel roofs I was thinking, I wonder if you put an electric Hot Dawg heate in to the attic space if a few hours of heating would clear the roof. Or would it just create a bunch of moisture and cause problems maybe it would be worth the couple hundred dollars to prevent yourself from falling off a roof.

 

[Admin]

We were up a few weeks ago after the 50" snow week and people had been clearing roofs. As I watched people shovel off the steel roofs I was thinking, I wonder if you put an electric Hot Dawg heate in to the attic space if a few hours of heating would clear the roof. Or would it just create a bunch of moisture and cause problems maybe it would be worth the couple hundred dollars to prevent yourself from falling off a roof.

It can. I have done that with the shop when it just did not want to go. However, I have only done it when temps were already at or going above freezing. I am not sure how well it would work if temps were below or well below freezing. Might just make a giant ice dam. I know the water was running pretty steady off the roofs before they finally slid.

-John

 

[mrbb]

Have a friend now in MTV's of Utah,in high snow area
heating under a metal roof, has caused her a lot of damage in the past, water gets under snow and freezes and lifts metal roof screws out, and makes large sheets of THICK ice that bond like glue to the roofAOL so I don't think that's a great idea.
Here in Pa, I know a lot of folks that use heat wires on roofs to try to keep edges free, orr gutters free flowing as it melts,
it works and doesn't, as them same wires that help case head aches if you want to use a roof rake, plus it makes water, which has bleed into many homes here due to melting and ice dams forming, puddling up water !

 

[Admin]

Have a friend now in MTV's of Utah,in high snow area
heating under a metal roof, has caused her a lot of damage in the past, water gets under snow and freezes and lifts metal roof screws out, and makes large sheets of THICK ice that bond like glue to the roofAOL so I don't think that's a great idea.
Here in Pa, I know a lot of folks that use heat wires on roofs to try to keep edges free, orr gutters free flowing as it melts,
it works and doesn't, as them same wires that help case head aches if you want to use a roof rake, plus it makes water, which has bleed into many homes here due to melting and ice dams forming, puddling up water !

Good call mrbb! I forgot to mention that my shop roof is just sitting on purlins. So the metal is fully exposed on the under side and thus will heat up well. I agree a metal roof that is sitting on a traditionally framed roof with 2x and sheathing could cause some serious issues! I also use the melting wire in some of the valleys that were created when we put the addition in and it works great.

 

[agriffinjd]

FWIW, I've never shoveled my roof, on my previous house I owned from 2008-2015, nor on my current house that I built in 2015. That said, it can't hurt it to shovel it, so who knows, maybe I'll shovel one side anyway. The south side though is three stories up (walkout basement) and I won't go on that side of the roof even on a hot summer day!

 

[G]

For best results if building - go with more pitch to start with. No dormers or other obstructions no matter how pretty they look. The less vents and pipes and whatever through the roof the better. Use dark steel or dark shingles. If possible face the building north or south so you get equal sun on both the east and west sides of the roof. I did all these things 15 years ago and my roof is still good and I never shovel it. A friend built a fancy roof with all kinds of angles and pitches and irregularities the same time I built. He has had continual problems with ice damns and leaks and big chunks falling off. He has to put on new shingles and or steel this summer. I will take functional over fancy anytime when it comes to roofs.

 

[Woodtic]

I should add that my roofs are dark green metal. I get them started by clearing the bottom 3' to expose the green roof to the sun. On a warmer day,the sun does the work for me. A lot of flat roof collapsed buildings are due to clogged or frozen roof drains. The snow starts melting and the water builds up on the low spot of the roof and has no place to go. I have trouble posting pics. I will send Addmin a pic of the snow melt system I work on at 150 N Michigan Ave in Chicago. Maybe he can post it for me.

 

[mrbb]

snow melting is a big issue here, as again rain gutters will fill and freeze, as many times the gutters drain pipes outlets block from snow or ice and BACK up gutters

and why so many folks in my area run them heat wires down the pipes to the outlets!!
to allow water on the roof to have a place to go, rather than just melt snow and have it re freeze over night!

its that water that builds near edges that gets under things and causes the damages here!
blocked up gutters don't help!

and I too agree BIG time, rather it work, than worry how it looks!

I have seen homes in AK< A frames where folks STILL use roof rakes due to excessive snow build up
and they have SERIOUS pitch on them things, need suction cups for feet to walk on them LOL

so some places I doubt there is ANY level of pitch that will save you!!

 

[garyl62]

All interesting comments, what I'm seeing it boils down to is not the load in most cases, but the freeze/thaw and ice/water issue that warrants the shoveling. Obviously that is an entire different reason that is very valid and I didn't think about until now. Guess I'll just wait till whenever the day comes for me to decide if I need to shovel or not. Sure hope things play out where that's a decision I need to make!