Hey guys- building a woodshed with six posts in a rectangular pattern, 8ft by 16ft with a post every 8ft. I need help with math equation to make sure everything's square. Thanks!
Need math formula help for laying out woodshed posts!
- Thread starter brooktrout
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no man said:
Not me bro. No carpenter here. When I built my 12 X 24 foot wood shed I just kept a level handy. After 20 years it leans a little, but hey. I do too.
No math needed, my shed is the same dimension but with posts every 4 feet. Just make sure the corners are square by measuring the sides vs the diagonals. Sides need to remain 8 and 16 feet and the diagonals should be equal.
The math - side A squared (8'sq. or 64) plus side B squared (16'sq. or 256) equals side C squared, the hypoteneuse in a right triangle (the diagonal). So the diagonal should be the square root of 256 + 64 (320), or 17.89 ft (about 214 7/8").
The math - side A squared (8'sq. or 64) plus side B squared (16'sq. or 256) equals side C squared, the hypoteneuse in a right triangle (the diagonal). So the diagonal should be the square root of 256 + 64 (320), or 17.89 ft (about 214 7/8").
Brooktrout, there's a rule that's used by carpenters all the time...the 3-4-5 rule. Trigonometry tells us that there is one of all possible right triangles (a right triangle being one with two sides perpendicular to one another, or at a 90-degree angle), which conveniently has sides with lengths in the ratio of 3:4:5. In other words, if you measure out from one corner 3 feet or 3 meters, or three miles or three of Jags' buck lengths, or 3 whatever, and then you measure out 4 of the very same thing on the other side you want to be square with the first, then measure the distance (hypotenuse) of the triangle between those two marks, if you get 5 of the same thing, then you've built a square structure. Do that on all four corners, and make sure to measure all the way across the two diagonals (they should be exactly the same), and you're go for throttle up...you have a square structure. Always use a level for checking plumb in both directions on the vertical members, and continue to check square & plumb as you build. Rick
Thanks guys. The 3-4-5 rule was what I was looking for. I knew it sounded familiar. To make things a bit more fun, the ground slopes three feet from front to back over the 16ft, and about a foot from left to right over 8ft. I've dug four of the six holes, by hand, which really sucks here in Delaware County, NY. About 8 inches of topsoil, then 12-14inches of clay, then BAM! you're bedrock, baby!
I build houses for a living and have for years and the easiest way to figure squareness is to cross tape like Be Green said. Oh and the 3 4 5 is right also but more work than nessacary because you still have to use the tape measure!!
And in the 8 x 16 case, the triangles are not 3-4-5 rule compliant. Different side ratios in that case.
BeGreen said:
You need to go back to school, BG...you don't have to be building a 3:4:5 structure for the rule to work on the corners of the structure you're building. A 3:4:5 triangle defines a right angle, regardless of the actual lengths of the sides. Rick
A 3:4:5 right triangle is just one of the ratios that can be achieved with a right triangle. It does not define a right triangle. Tell me how a 8' x 16' sided triangle fits into this rule where side A= 1, side 2= 2 and the hypotenuse = 2.236. If multiplied out that becomes a 3:6:6.7 triangle.
Or what if both sides are equal? Then 3:4:5 doesn't apply at all. If the shed were 8' x 8' then the hypotenuse would be 11.31. I'm not a math genius by any means, but this is common sense.
Here's a graphic aid.
Or what if both sides are equal? Then 3:4:5 doesn't apply at all. If the shed were 8' x 8' then the hypotenuse would be 11.31. I'm not a math genius by any means, but this is common sense.
Here's a graphic aid.
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BG, all I'm saying is that you said "not 3:4:5 compliant"...of course not every right triangle is a 3:4:5, and of course there are an infinite number of other configurations...all I'm saying is that the 3:4:5 rule can be used to verify whether or not a corner is square. Stand at the corner, measure one way 3 somethings (don't have to go all the way to wherever it goes), make a mark, OK, now measure the other way 4 of the same somethings, make another mark. Now measure the distance between the two marks. If it's 5 somethings, you've constructed a square (right angled) corner. That's it, that's all there is to 3:4:5. Rick
EDIT: I never said 3:4:5 defined a right triangle...I said it defined a right angle.
EDIT: I never said 3:4:5 defined a right triangle...I said it defined a right angle.
Ah, now I've got it Rick. I didn't apply that rule when setting up the shed because although I had a square corner, that didn't mean it was aligned with the opposite one. But you are correct. I guess I just had different carpenters teaching me. We always measured and equalized the diagonals.
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Rick
I've read so many puns on this forum it's rediculous! Maybe we should have a separate forum just for pun.
Nah, that would belong to the Punsylvania Puntificators forum. And they don't use computers. Puncils only. :lol:
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