Squaring Poles for a Building

[tinlizzie]

Hi, I am trying to build a building, 16'x24'. I am having trouble getting the post square. I am putting post on the corners, 4 in all. This will be an enclosed building for storage. Thanks for any help. LIZ

[midwilshire]

If I understand you correctly, you're trying to make sure the corners are square so that you know where to put in your corner posts.

One way to do it is to place stakes in the ground where you think one side of the structure should be. Whatever layout works best - Perhaps you know that you want the 16' side in a particular location. Put the stakes there.

Then, you can use the Pythagorean Theorem to figure out what your diagonal length should be. That'll tell you about where to put the third stake. In case you don't want to figure out the theorem, I'll just tell you that the diagonal on a 16 x 24 structure should be 28' 10". Once all four stakes are in, both diagonals should be equal. That is, they should both be 28 feet, 10 inches. That should get you square.

By the way, in case you don't want to mess around calculating the Theorem, just make sure your diagonals are equal. It doesn't matter what the number comes out to; once both diagonals are equal, you must be square.

Then you replace the stakes with your posts, and you're in business.

[Bird]

</font><blockquote><font class="small">In reply to:</font><hr />
It doesn't matter what the number comes out to; once both diagonals are equal, you must be square.

[/ QUOTE ]

That Theorem only works if you have a 90 degree angle to work with. Suppose you place your first two stakes for one side, then you place a third stake, but it's more or less than a 90 degree angle, so you measure the diagonal, but if you don't also measure the sides, can't you wind up with a trapezoid that is not a rectangle?

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] I thought that using A square Plus B square = C square GAVE you the first true 90-degree angle that you were looking for as a starting point. Once you set that first corner, THEN the diagonals must be equal to get the second and the third and the fourth corners. The PT is the one to use, just as he said. [img]/forums/images/icons/tongue.gif[/img]

[Bird]

You're right, Dave. Let's say you place two stakes 24' apart for one side. Now when you calculate the length of the hypotenuse (or diagonal) to be 28'10" (plus a tiny bit more than a tenth of an inch, if you want to be exact [img]/forums/images/icons/wink.gif[/img] ), you go to one of those stakes and anchor one end of your measuring tape at that stake. Then you take the other end and where are you going to put that third stake? I still don't see how you can determine that without also measuring off the 16' side. But when you measure out the 28'10" from the first stake and 16' from the second stake, the point where they cross is the place for the third stake.

[jml755]

Easiest way I've found to set up a square building is this:
1 - Put 2 stakes along the line of one long wall.
2- Stretch a mason's line string between the 2 stakes. This will be the outside face of your corner posts on that wall line.
3 - put in the 2 corner posts on this wall at the desired distance apart.
4 - Twist each post until the outside face just touches or is slightly off of the taut line. This will ensure that the posts are square to each other.
5 - Plumb each post (in turn) in 2 directions. Nail 2x4 in 2 directions approx. 6' off the ground to the post and anchor other end to a stake in the ground to maintain plumb. It is best to have the 2x4's and stakes in place while plumbing the post, so a c-clamp can be applied when the post is plumb if you're working alone. Or have a helper nail to the stake while you hold the post plumb. This step is actually easier than it sounds.
6 - Use a 3-4-5 triangle (pythagorean theorm) to set the line for the short wall and determine where the 3rd post is. Run another line between stakes along the short wall. Best way to do this. Put a stake outside the long wall, making sure it is a short distance toward the far post. Tie a string to it and run it along the short wall, so it "wraps" and hugs the face of the corner post as it goes along the short wall side. Put 2 stakes with a cross board past the other post on the short wall so the post will end up somewhere between the 2 stakes (batter board). Clamp the other end of the string to the cross board where you think it should be for a 90 deg. wall. Now, measure a multiple of 4' (say 8', 2x4) along the first wall. Measure the same multiple of 3' (6', 2x3) along the short wall. Mark these 2 points on the strings with a fine tipped marker. Measure diagonally between the 2 marks. Should be 10' (2x5). Adjust the position of the string clamped to the batter board until it's exactly 10'. You now have a perfect right triangle layout for the 2 walls.
7 - Set the 3rd post along the short wall string at the desired distance. Plumb and anchor as above.
8 - Set the 4th corner post, using the same method as above at the other short wall. This should get you pretty close.
9 - Check for squareness of building by comparing the 2 diagonals. I usually end up having to adjust just the 4th post.

I've used the above method many times. Depending on how careful you are with the measurements, you should be able to get withing 1/8" of square on a building your size. That's plenty good enough for rough framing.

The 3-4-5 triangle is easy to remember instead of multiplying out odd measurements, calculating square roots. I use it all the time in units of ft, inches, yards.

[jml755]

Another thing to remember is to check the wall lengths and diagonals at the top of the posts where you will be putting headers. Sometimes you can have a perfect square at the lower level of the structure, but due to an error in your "plumb" reading or a bowed post, you may have a problem up top, and that is more critical in my opinion. You can usually "persuade" a post to line up with a header to compensate for a small error but the biggest risk is if you're putting in trusses and laying plywood for a roof. 4x8 sheets are 4x8 and if the roof ain't square, you'll see it when you put down the panels. On a small building like yours, it probably won't be an issue.

[egon]

Did you meaqn getting the location for the posts in the proper spot or did you want to make the posts square?
[img]/forums/images/icons/grin.gif[/img]
Egon [img]/forums/images/icons/grin.gif[/img]

[Pat]

But wait there are even more ways to understand "square" in this building context.

Bird, Don't put in the third stake by eyeball place it after doing the math thing.

So long as both diagonals are equal the building is square but... how do you quickly and easily get them equal?

If you lay out a right angle by using a measureing tape to construct a 3-4-5 right triangle and put a wall's line over each of the right angle lines you are off to a good, easy, and simple start. You can them measure out the length of the walls and place more corner stakes. This is a good time to measure the two diagonals as a check to just be sure. These measurements do not need to be perfect, just equal to a 1/4 or 1/2 inch is usually more than good enough.

If you use a PHD on a tractor to auger the holes or a hand held motorized auger, I recommend oversizing the holes to permit slight adjustment of the poles. Use a level on the poles. Set it vertical and do each pole twice, 90 degrees apart to ensure they are plumb. If setting in concrete you might want to consider bracing the poles to stakes in the ground to hold the poles vertical while waiting for the concrete to gain sufficient strength. (concrete attains 90% of its final strength in 28 days but the posts should not need props after 3 days, just don't stress them prematurely.)

Pat

[tinlizzie]

Hi, Thank You so much, I was trying to put the front post in and then measuring from there back 24' [img]/forums/images/icons/smile.gif[/img] It was much easier the way you said. It rained all day but I did manage to get 2 of the post in. LIZ