Should I worry about the weight of my new roof?

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Old 07-31-12, 09:09 AM
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Should I worry about the weight of my new roof?

Doing some calculations:

New Roof:
Timberline shingle 73lb / 33.3 ft sq = 2.21 lb/sq ft (Lifetime Timberline Natural Shadow Weathered Wood Shingles-0603737 at The Home Depot)
3/4 plywood = 2.3 lb sq ft (What is weight per square foot of Plywood)

2000 sq ft roof x (2.3 lbs sq ft plywood + 2.21 Shingle) = 9020 lbs

Original Roof:
Wet Cedar shakes weigh 3lb/ sq ft x 2000 sq ft = 6000 lb
Dry cedar shakes weigh 2 lbs/ sq ft = 4000 Lb

Weight cedar shakes: Cedar Shakes and Shingles are ma

So I am wondering if the additional weight, equal to 1-1/2 small cars, is going to be a problem for my house? Should I have gone with 5/8 plywood and 20 yr shingles which weigh 10lb less per pack.
 
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Old 07-31-12, 10:24 AM
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Any roof in sound condition should be able to support one layer of even the highes quality asphalt shingles without trouble. If you had asked about putting your new shingles on top of two already existing layers I would have said "yes, problem" but a single layer is no problem.
 
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Old 07-31-12, 11:42 AM
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I am not worrying about the roof supporting the shingles, I am wondering if my house can support what seems to me to be a much heavier roof. Plywood and asphalt seem to weigh about twice what cedar weighs.

The plywood will add some strength of its own, but will make the house more top heavy also.

This is more of a theoretical question but I am just wondering.
 
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Old 07-31-12, 03:27 PM
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While you're worrying with calculations, think about where the weight is......on the outer perimeter of the house, on vertical framing members, which transmit this weight safely to a concrete foundation and thus to the ground. Rest easy.
 
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Old 07-31-12, 04:15 PM
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If you really want to get nervous consider that when a house it being built they often crane in the sheetrock and it all in one or two piles. Not only is it a couple tons of weight but they set it in one spot. Not spread out evenly about the house.

I have also seen houses with three layers of asphalt shingles. Code and common sense says three layers is too much I've never actually seen a house damaged by all that weight. Especially remarkable when you think the roof also carried winter snow loads which around here are usually wet, heavy snows.
 
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Old 08-01-12, 07:34 PM
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If worrying about things makes you feel better, then yes, by all means go ahead and worry about the extra weight of the new asphalt shingle roof.

On the other hand, the logical thinkers among us would look at it this way: Adding an extra 1.5 lb./S.F. to a roof and structure that were originally designed to support anywhere from 40 lb./S.F. to 70 lb./S.F. is like throwing a bucket full of ping-pong balls into a loaded dump truck--the truck (and your house) will just keep happily chugging along as if nothing was added at all.
 
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