How badly can golf ball sized hail damage a roof?

March 29, 2006 11:29 AM

Is it feasible that a short (probably under 5 minutes) but rather heavy hail storm of golf ball-ish sized hail would damage a shingle roof to the point where it would need to be replaced?

My wife and I are very new homeowners (a little over a month) and a couple of weeks ago we had a hail storm. It didn't last too long but was pretty heavy and the hail was in the walnut to golf ball sized range. (here's a video of the storm). Afterwards, we thought we'd escaped with no other damage than a couple of window screens knocked out, but relatives recommended that we have an insurance adjustor take a look at the roof to make sure. To our surprise he said that he'd found enough damage that he thought it would need to be replaced. Does this seem reasonable? I mean, it would seem that the insurance adjustor would have no reason to recommend it if it wasn't necessary, but I was just wondering if it would be uncommon to have to completely replace a roof after a storm of that intensity.

posted by shinji_ikari to home & garden (13 comments total)

A five minute hail storm (of golf ball size hail) is by no means "short." Very definite roof damage potential there.
posted by AstroGuy at 11:37 AM on March 29, 2006

I'm with AstroGuy.
posted by rinkjustice at 11:44 AM on March 29, 2006

i would say yes and these somewhat official sounding science folks seem to think that hail falls fast enough to dent aluminum siding and cars. i did not read it all that carefully there was something about a terminal velocity of approximately 40mph for a 1 inch hailstone, in theory. it does not seem like a stretch that it would damage shingles as well.
posted by phil at 11:59 AM on March 29, 2006

I agree. I've had a roof totalled because of hail. It doesn't take much. I don't know the exact criteria the adjustor uses, but it's based on a certain number of hits in an area of a certain size. Sort of like the way LCD manufacturers will replace a screen if it has a certain number of dead/hot pixels total, or a certain number clustered in one region of the screen.

The thing about an adjustor totalling something is that he is not saying "it has been rendered completely useless," he is saying "cheaper to replace it than fix it."
posted by adamrice at 12:04 PM on March 29, 2006

More than reasonable assuming asphalt shingles. Heat and UV are the key degraders of asphalt shingles and if you're getting hail in March I'm guessing your are located somewhere that gets lots of sun and heat. The initial downburst will cool your roof dramatically making it brittle (and the older the roof the brittler). Then the continuing hail (and golf balls are good size) can crack the shingles letting water in. Even worse is future straight line winds could peel off pieces of the damaged shingles.
posted by Mitheral at 12:05 PM on March 29, 2006

Yeah, I believe it. But you didn't say what kind of damage he discovered. I mean, are there shingles that were torn? Or was it tearing or deformation of the substrate of the roof -- the plywood that the roof is built on? Or some of the cresting and weather stripping? That's the first thing you need to find out.
posted by SpecialK at 12:07 PM on March 29, 2006

Is your insurance going to pay for a new roof? If so, let them do it now, because if you don't, will they tell you later "we would have fixed it then, but you're on your own this time."?
posted by bilabial at 1:35 PM on March 29, 2006

As bilabial says, if the insurance company wants to give you $ to fix the roof, by all means take the $ and fix the roof.
posted by thomas j wise at 1:41 PM on March 29, 2006

Hail can badly damage cedar shingles too. (And watching that video of the storm you had, I'd be surprised if your roof wasn't damaged.) I know from experience about cedar. It's how I learned to roof a house.
posted by lobakgo at 1:53 PM on March 29, 2006

Do it. I've been there, and golf-ball size hail is more than enough to destroy an asphalt shingle roof, and it's better to take care of it now than after you've taken water damage to your ceilings.

Think of it this way - you're getting your roof replaced for the price of your deductible+the inevitable jacking up of your insurance rate (because you dared to make a claim). You're coming out ahead here, in all likelihood.
posted by deadmessenger at 2:37 PM on March 29, 2006

a golf ball has a volume of about 40.63 milliliters, water has a density of 1g/mL, giving it a mass of .0406kg
since F=ma, and gravity is the only outside force acting on the hail (we are ignoring air resistance) it should strike your roof with a force approximatly equal to .4 N. I cant imagine that would be enough to do any damage....but the thread opinion is that im wrong. apparently shingles are fragile. Perhaps repeated small blows like that could cause some damage....but i dont know.
posted by I_am_jesus at 5:21 PM on March 29, 2006

actually, im wrong. i forgot about impulse and all that. disregard my last comment.
posted by I_am_jesus at 5:26 PM on March 29, 2006

gravity is the only outside force acting on the hail

Gravity and wind my friend. A good stiff 45mph wind and some hail can play havoc on cars, roofs, vegetation, you name it.
posted by fshgrl at 7:42 PM on March 29, 2006