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Irving
03-16-2016, 23:14
Find the area. Post up your answers.

https://lh3.googleusercontent.com/NVBzfkleiXMUJRgtXSECsqtweqxquO1NFOJUakGTukL-Tm13Ny20Wf6dsVZQ2JRoXdKUl2oD_S9RZq3a6pOGpoBgHuCnDv qiCosr9tpdAyckAQFU4n8F0vGT2N7NN8b-aE_db3OXmdNZr-czrvSad-nEuEJIlPU9UDomYhInM_z0eiPSMCvM1Vzm1yFsY-46OZLHGgbx1tXL5W9gXmPWYn7orTkJaq5dTgaeWP23gVer7cRn Ki9msa8WrOk3d-Qmn8nJAM5Es6twWiVVOuvhZSX6eg55wYqkHf_ZfT8ykqZxb6tE rBlNa9uido4uZGB0_DrhMFKvaLPTGZYAsBzYgI9Bt4gohiX4Cl XkkM1t-4Ul4JV_485-2xKQ620enUFed8iuzh9-WzTlJPg-6eWXtR-SUIT1LtjsgMJIuVclyArCz01HxTnVUpvUBAHdWXHpxecGzpeEL r6JGuoI2e_-CV1cDx7Yw6PX4nRVKTJ3nNfNBruwpmJnjYAlNJrv0dGbHl8mOr u_QuT18f-f7Ji4Rw58r1wgeN2yvpTOUS_BFxsMRGYZLZfvpnzUcQz7HVY7I c3kGg=w1528-h956-no

HoneyBadger
03-16-2016, 23:27
Are you posting up your homework because you're too lazy to do it?

Irving
03-16-2016, 23:29
No, I already did it, but then I started to question whether I had enough information to do it correctly or not.

HoneyBadger
03-16-2016, 23:31
Also, without knowing the roof pitch, it's impossible to tell the sq footage of roof.

Great-Kazoo
03-16-2016, 23:32
$4700 in roofing materials + labor . That doesn't include decking. Don't forget gutters & down spouts. Which will get trashed by the tear off crew. Throwing another $4200 in materials.

Irving
03-16-2016, 23:33
This is a roof with a slope, so you can't just turn this into two rectangles of 34'4 x 23'5 and 13'7 x 33'4.

davsel
03-16-2016, 23:33
42

Irving
03-16-2016, 23:35
Also, without knowing the roof pitch, it's impossible to tell the sq footage of roof.

It shouldn't matter since all the measurements were taken on the surface of each "shape." You're looking at the actual measurements, so I guess the eaves would be in scale with the ridges, and the hips in scale with the valleys. On this roof anyway, where everything is the same slope.

HoneyBadger
03-16-2016, 23:35
But if the roof were flat, the area would be 1001-ish sq units (sq ft... I assume) Take the bigger box (40'8"x 37') and subtract the two smaller boxes (23'5" x 6'4" and 7'6" x 13'7")

HoneyBadger
03-16-2016, 23:39
Also, without knowing the roof pitch, it's impossible to tell the sq footage of roof.


This is a roof with a slope, so you can't just turn this into two rectangles of 34'4 x 23'5 and 13'7 x 33'4.

Exactly. Because it has slope, there is a third measurable dimension that the above "two rectangles" don't account for. Need to know the pitch(es) of the roof if you are looking for a surface area measurement.


It shouldn't matter since all the measurements were taken on the surface of each "shape." You're looking at the actual measurements, so I guess the eaves would be in scale with the ridges, and the hips in scale with the valleys. On this roof anyway, where everything is the same slope.

Are you saying you measured from eve to ridge here? If so, and the pitch is consistent through out, then the rectangles method will work fine.

Great-Kazoo
03-16-2016, 23:40
But if the roof were flat, the area would be 1001-ish sq units (sq ft... I assume) Take the bigger box (40'8"x 37') and subtract the two smaller boxes (23'5" x 6'4" and 7'6" x 13'7")

It's Not Flat, stop trying new math on the problem

HoneyBadger
03-16-2016, 23:41
42
Common Core math.

http://www.kappit.com/img/pics/201509_1635_afece_sm.jpg

HoneyBadger
03-16-2016, 23:42
It's Not Flat, stop trying new math on the problem
Don't worry Kazoo, I'm a rocket scientist. [LOL]

Irving
03-16-2016, 23:47
$4700 in roofing materials + labor . That doesn't include decking. Don't forget gutters & down spouts. Which will get trashed by the tear off crew. Throwing another $4200 in materials.

Knowing the rough size of the roof, this isn't actually that far off.


Exactly. Because it has slope, there is a third measurable dimension that the above "two rectangles" don't account for. Need to know the pitch(es) of the roof if you are looking for a surface area measurement.



Are you saying you measured from eve to ridge here? If so, and the pitch is consistent through out, then the rectangles method will work fine.

You have to find the area of each shape individually because of the slope. The measurements are actual, just drawn on an image that is "in scale" so it looks the same as if you were viewing the roof from a bird's eye view. I didn't measure eave to ridge, except for along the hips and valleys (which isn't helpful). A friend suggested that Wolframalpha can do this for me, and I may start using that program to save time.

HoneyBadger
03-16-2016, 23:48
So how far off was my 1001sqft guestimate?

Irving
03-16-2016, 23:53
Well, I'd say over 900 sq/ft off, but I'm not sure I'm comfortable with the way I came to my answer. I'm going to see what wolframalpha says.

HoneyBadger
03-16-2016, 23:59
Well, I'd say over 900 sq/ft off, but I'm not sure I'm comfortable with the way I came to my answer. I'm going to see what wolframalpha says.
Uhhhhh wtf is the roof pitch?

HoneyBadger
03-17-2016, 00:02
I'm laying in bed with my iPad after a few glasses of scotch. Math is a bit harder, but inventing things is easier... Got any niche problems that need solving?

HoneyBadger
03-17-2016, 00:04
So what was the roof pitch? Was it consistent throughout? That will make things easier.

HoneyBadger
03-17-2016, 00:07
The triangles you measured out are simple trig, but the other shapes are a bit tougher...

Irving
03-17-2016, 00:08
I was doing something wrong, so I'll have to use the Heron formula http://mathworld.wolfram.com/HeronsFormula.html.

HoneyBadger
03-17-2016, 00:09
If it was anything like a standard roof, (and now understanding how you got the measurements in your sketch) I'd guesstimate 1338 sqft.

Irving
03-17-2016, 00:09
The roof pitch is 5/12. How will you use that information to better solve the problem?

HoneyBadger
03-17-2016, 00:10
I was doing something wrong, so I'll have to use the Heron formula http://mathworld.wolfram.com/HeronsFormula.html.
That is the most complicated way I've ever seen to derive the area of a triangle...

HoneyBadger
03-17-2016, 00:11
The roof pitch is 5/12. How will you use that information to better solve the problem?
Okay, now my guesstimate is 1320 sqft. [Neene3]

Irving
03-17-2016, 00:12
The triangles you measured out are simple trig, but the other shapes are a bit tougher...

When you say simple trig, would you say it's simple enough to do with a cell phone calculator, while standing on a roof? I'm not being sarcastic, that's an honest question.

Irving
03-17-2016, 00:13
That is the most complicated way I've ever seen to derive the area of a triangle...

Show me how you're getting the area of the very top triangle with sides of 17, 17, 23.41.

HoneyBadger
03-17-2016, 00:19
I'm on my iPad and can't do real math, but it should be...


hold the phone.... I can't trig on an iPad...

HoneyBadger
03-17-2016, 00:35
Oh hell... Without knowing at least one more angle measurement, I don't think I can do it.

HoneyBadger
03-17-2016, 00:40
Dammit. Math is telling me that your measurements don't add up.

HoneyBadger
03-17-2016, 00:45
Okay, well, the top triangle should be 144.5 sqft. (17x17)/2= 144.5. That's the easy one. I was getting sidetracked with the other shapes.

You can do simple math here because 17x17 tells you that the angle between them is 90 degrees. Just multiply to get the area of a 17x17 square, then divide by 2 to get half do that square.

Irving
03-17-2016, 00:45
Okay, I figured out exactly where I've been going wrong now. Thanks for playing along everyone.

Irving
03-17-2016, 00:48
Okay, well, the top triangle should be 144.5 sqft. (17x17)/2= 144.5. That's the easy one. I was getting sidetracked with the other shapes.

I think we're lucky that triangle happened to be a right triangle. I've been getting 144 for that triangle as well.

HoneyBadger
03-17-2016, 00:49
Everyone? This may as well be the PWT! [LOL]

HoneyBadger
03-17-2016, 00:50
I think we're lucky that triangle happened to be a right triangle. I've been getting 144 for that triangle as well.
Yep, right triangle is easy. I am still struggling with how to get some of the other shapes... I think you'd have to break them down into smaller triangles to get areas.

HoneyBadger
03-17-2016, 01:01
Well, my iPad battery is down to 3%. Good luck. I'll check back in the morning to see how wrong I was... [ROFL1]

sniper7
03-17-2016, 04:00
1400sqft of materials should cover it.

Irving
03-17-2016, 06:30
How is everyone finding the area of the parallelograms without the height measurement?

TRnCO
03-17-2016, 06:53
without taking height into it, I come up with 1256 st. ft. All I did was break it down into two boxes, one of 34.4' x 23.5' and the other 33.4' x 13.7'. No need to worry about all the other angles, except for the fact that they are adding height, you can figure that part out.[Coffee]

Bailey Guns
03-17-2016, 07:00
Jesus...not even 6am and I need a shot of bourbon already after reading this thread. Math sucks.

hghclsswhitetrsh
03-17-2016, 07:36
There's an app for that.

Great-Kazoo
03-17-2016, 08:11
. Math sucks.

Let's go shopping !

Dave_L
03-17-2016, 08:54
Just deny the claim and move on.

muddywings
03-17-2016, 09:19
This is simple.
Add up total length on one side multiply by total width of the other side. Don't remove those upper right and bottom left corners. Then find the store that will refund unused bundles of shingles. You will probably have enough to account for slope by not removing those two corners.
Boom done...

ETA: Still don't understand why pitch matters
ETA: never mind, now I think I know. Still kinda waking up

cstone
03-17-2016, 09:23
My 1 minute estimate ... 37x42=1554 sq ft.

BUC303
03-17-2016, 09:53
without taking height into it, I come up with 1256 st. ft. All I did was break it down into two boxes, one of 34.4' x 23.5' and the other 33.4' x 13.7'. No need to worry about all the other angles, except for the fact that they are adding height, you can figure that part out.[Coffee]


This is a roof with a slope, so you can't just turn this into two rectangles of 34'4 x 23'5 and 13'7 x 33'4.

I did the same thing since he asked for the area of a 2 dimensional shape or 1,256.63 sq. ft.

spqrzilla
03-17-2016, 11:02
Common Core solution: Racist!

newracer
03-17-2016, 11:44
1361 using http://www.calculator.net/roofing-calculator.html

Irving
03-17-2016, 11:48
1361 using http://www.calculator.net/roofing-calculator.html

That is probably pretty close. If anyone on here knows a way to determine the area of a parallelogram with only knowing the perimeter, I'm listening.

newracer
03-17-2016, 11:56
You need to know an angle.

Irving
03-17-2016, 11:58
You need to know an angle.

Sounds like I'm going to have to start measuring the height on each parallelogram then.

HoneyBadger
03-17-2016, 12:06
Ask one of those fancy college-educated millennials. They have a really solid understanding of simple math, right? #FeelingTheBern #NoWait... #ThatsJustTearGasInMySafeSpace

Irving
03-17-2016, 12:26
Ask one of those fancy college-educated millennials. They have a really solid understanding of simple math, right? #FeelingTheBern #NoWait... #ThatsJustTearGasInMySafeSpace

Good idea! When the adjuster says, "Hey, can you get me the total square footage in the next few minutes so I can settle this on site?"
I'll just say, "Just have the government do it, man. The homeowner should do their fair share of math man."

:D

asmo
03-17-2016, 12:36
34.333 * 37 = 1270.321


If the measurements are not wrong (which, geometry says they are in my mind), then you need to account for the gap between the 6.333 and the 7.5 measurement (1.17' * 13.583)... Don't see how it can be 34.333 on one side of the rectangle and 33.333 on the other, but have 6.333 and 7.5 offsets -- there is .17 missing somewhere.
13.583 * 1.17 = 8.867


1270.321 - 8.867 = 1261.454


What am I missing? Its just a simple box.

asmo
03-17-2016, 12:39
That is probably pretty close. If anyone on here knows a way to determine the area of a parallelogram with only knowing the perimeter, I'm listening.

"A parallelogram is a 4-sided shape formed by two pairs of parallel lines. Opposite sides are equal in length and opposite angles are equal in measure. To find the area of a parallelogram, multiply the base by the height."

Irving
03-17-2016, 12:46
34.333 * 37 = 1270.321


If the measurements are not wrong (which, geometry says they are in my mind), then you need to account for the gap between the 6.333 and the 7.5 measurement (1.17' * 13.583)... Don't see how it can be 33.333 on each side of the rectangle, but have 6.333 and 7.5 offsets.
13.583 * 1.17 = 8.867


1270.321 - 8.867 = 1261.454


What am I missing? Its just a simple box.

Just think of a birds eye view sketch of a pyramid, where you have all the measurements of the eaves (base) and all the hips (ridges) going to the top. You couldn't just take the b x h of the perimeter measurements for the total area. You'd have to measure the area of each triangle individually, then add them together.

asmo
03-17-2016, 12:58
Just think of a birds eye view sketch of a pyramid, where you have all the measurements of the eaves (base) and all the hips (ridges) going to the top. You couldn't just take the b x h of the perimeter measurements for the total area. You'd have to measure the area of each triangle individually, then add them together.

You are asking for the surface area of the full pyramid in that case, of which the measurement of the base would only give you one side (the bottom/base). I see what you are saying, but I thought that was what you were asking for.

Yeah maths!

Irving
03-17-2016, 13:05
Just so there is no confusion, I'm not trying to Huck Finn anyone into doing my work for me. I just got to thinking about the way I was measuring and wanted to see if the information I had obtained was enough to accurately calculate the surface area of the roof. Turns out that there isn't enough info and I'll have to change my method up a bit. Always striving to improve right?

Maybe once Bernie Sanders is elected, I can get him to outlaw hip roofs, especially on rich people's homes.

TFOGGER
03-17-2016, 13:08
Pie are square? I thought pie were round...

51 Square of shingles, round up to 54 to account for waste...

davsel
03-17-2016, 13:17
Cut the Triangle in half to figure ridge height using a^2 + b^2 = c^2 method for right triangles.

17’ x 17’ x 25’5” Triangle
23’5” = 23.416’ / 2 = 11.708’
17^2 – 11.708^2 = 151.915
SQRT(151.915) = 12.325’ = Eve to Ridge Height (lower ridge)

12.325 * 11.708 = 144.306 sq ft (17’x17’ x 25’5” Triangle)

Use similar method to figure other ridge heights.

Irving
03-17-2016, 13:24
That only works on that triangle because it happens to be a right triangle. I could draw right triangles inside the parallelograms, but there isn't a good way to determine the measurements of the two sides of triangle I just created. You could get close if you measured the lines on the paper as a known distance, then measured the new lines, but it still would not be correct due to the way the the diagram is rendered.

davsel
03-17-2016, 13:32
The 17x17 is not a right triangle (not quite) according to your measurements.
but you can turn it into two right triangles and get the ridge height.

Irving
03-17-2016, 13:35
Yeah, they usually aren't. To complicate things further, I changed at least two measurements on this diagram, just for consistency. One of the parallelograms has different sides of 17 and 17'2, which is how it actually measured.

Houses with build overs get all kinds of weird shapes and measurements.

The real lesson everyone should take away from this thread is that Eagle View is worth every penny!

Jamnanc
03-17-2016, 17:03
I could see if a guy at work could toss it into agtek if it's important. I'd need a guesstimate of the height from valley to ridge. Otherwise, run it flat and add 20%.

Guylee
03-17-2016, 17:04
That's math. I don't do that.

Wulf202
03-17-2016, 17:08
What's the adress? I'll eagle view it

Irving
03-17-2016, 17:08
I could see if a guy at work could toss it into agtek if it's important. I'd need a guesstimate of the height from valley to ridge. Otherwise, run it flat and add 20%.

It's not important at all. I just wanted to see what answers people got and how they got them.


That's math. I don't do that.

I'm just happy to see that not everyone jumped in with an instant answer and bragged about how much smarter they are than me.

Irving
03-17-2016, 17:09
What's the adress? I'll eagle view it

No sir, that costs money, and if the cheapo insurance company has an issue, then they can Eagle View it.

RblDiver
03-17-2016, 17:17
How is everyone finding the area of the parallelograms without the height measurement?

Even more complicated, they're not even parallelograms, but rather trapezoids, with the two opposing sides at different lengths.

Gman
03-17-2016, 17:24
[pick-me]


It's a trick question.


How can we find the area when you haven't given even the slightest hint as to its location?

Jamnanc
03-17-2016, 18:25
This is the product we use for earthwork estimating. 64444

I'm a dummy, so I turn everything into rectangles and cubes. Close enough most of the time.

Irving
03-17-2016, 22:15
Oh yeah, squares all day long when possible.