Don’t let your roof collapse on your head!

Not by Fire but by Ice

THE NEXT ICE AGE - NOW!

Discover What Killed the Dinosaurs . . . and Why it Could Soon Kill Us

 
Google
 
Web www.iceagenow.com
BACK TO HOME PAGE

.
Don’t let your roof collapse on your head!
Also see e-mail in disagreement (below)
______________________________




E-mail from a reader:

Dear Robert

Please let people have this information on your site. Maybe just one paragraph to GRAB their attention and motivate them to action?

 A NORMAL ROOF LOAD IS 40 LBS/Sq. Ft.

1" of snow is 1 Lb/Sq.Ft. THAT MEANS ANY ROOF CAN COLLAPSE AFTER JUST 40" OF SNOW!

And that’s dry snow.  Most will collapse before 40” of wet snow.

Thank you so much

Stephanie Relfe
www.relfe.com

Note from Robert: I agree with Stephanie. Snow can weigh as little as 7 pounds per cubic foot, but a more average snowfall can easily weigh 15 lbs./cu. Ft.
Compacted snow can weigh 20 pounds or more.

And if it should rain, snow can act like a sponge and get heavier … fast.

So be ready to brace up your roof or have it cleared.

Source: http://wiki.answers.com/Q/How_much_does_a_cubic_foot_of_snow_weigh

                                                  * * *

Another reader wrote in with a vehement protest:

Sorry to disagree with the information about what a "normal" roof can
hold. While it is true that a great number of roofs are constructed to
the standard of holding up a minimum of forty pounds per square foot,
that is by no means the last straw.

Virtually any 40 Lb. roof will take around a 100 psf or so load without
collapsing. In addition, roofs in higher snow fall regions are
constructed to withstand a load equivalent to the greatest conceivable
snow fall of that region, while experiencing the highest conceivable
wind load for that region, during the greatest conceivable earthquake
for that region.

Where I live, in Caldwell Idaho, a modern roof (the whole building) is
constructed to resist a 40 Lb snow load during a hundred mile per hour
wind in the midst of a 7.0 earthquake. (specs may be inaccurate but are
representative of the design criteria)

I have worked on old houses that simply spanned 2x4 rafters from wall to
peak with no concern for "maximum span" ratings. There are many of these
houses still in existence and despite their obvious, radically
substandard structures, they've shrugged off winters for 50 to 80 years
while developing an amazing amount of sag.

The idea that the typical modern roof will collapse under any
foreseeable snow fall is just plain silly.

Please, remove or update that posting. The house I live in is itself at
least eighty years old and a prime example of what I'm writing about. If
I were to tear off the roof framing and replace it with run of the mill
modern trusses I would improve it's strength by a factor of at least
four or five, and no, I'm not concerned about it collapsing now.

Joe Sevy

Note from Robert: I was raised in Vermont and went to school in Minnesota. I've seen too many roof collapses - especially on barns - to take any chances.

                                                 * * *

Words from yet another reader:

Hi, Robert.

I don't mean to pile on about roof structural limitations vis a vis snow
loads but the worst situation is a series of freeze/thaw cycles with on
& off heavy snow fall.  That happened to me a few years ago.  My roof is
designed specifically for harvesting rain and snow melt so it's
relatively flat.  In spite of the fact that the roof is as strong as
some small bridges, I got worried and went up to check on things.  I
spent the rest of the day breaking up 4 - 5 inch thick ice under about
two feet of very dense, wet snow.  Scary!

Aram Paquin

 

 

 



.
.

BACK TO HOME PAGE

Order Book I Q & A I Book Reviews I Plant Hardiness Zone Maps I Radio Interviews I Table of Contents I Excerpts I Author Photo I Pacemaker of the Ice Ages I Extent of Previous Glaciation I Crane Buried in Antarctic Ice Sheet I Ice Ages and Magnetic Reversals I It's Ocean Warming I E-Mail Robert at rwfelix@juno.com l Expanding Glaciers