Does anyone out there have any advice for measuring out the placement of concrete tubes when the 4×4 posts they’ll hold have to be a specific distance apart? I’m building a 8 x 12 storage shed with a post in each corner and one halfway along each 12′ side.
Thanks!!
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This is a pain, because they are round and it's hard to register the middle. But I've heard of people doing this: First dig the hole approximately where the tube will go. Build the outer frame of the structure (headers, etc.). Clamp a post (e.g. 4X4) in place. Set the tube under the mock post so it looks perfect. Remove mock post. Fill tube with concrete. Install real post.
Basically, you are fitting the tube to the post (easy) rather than the tube to some theoretical layout line (harder).
String line the center of the posts, all four sides.
Measure the OD of the sono tubes, a 2' sonotube OD will be about 24 1/2".
Use a framing square held to the ST so the ST is inside the corner of the square. Mark the radius (12 1/4" in this example) from the square on to the ST on both legs. Rotate the square around the tube till one 12 1'4" tik is on a mark on the tube, make a third mark at the 12 1/4" mark, repeat for the fourth mark and repeat again to insure that the first mark is close to 12 1/4".
This will give you (close enough) marks on the sonotube each 90* around indicating the centerpoint of each tube.
Center the tubes under the string lines using two opposite marks. use the other pair to set the post OC dimension.
Brace the sonotubes in place and use the marks to Ballpark your hardware on the tube. Check the hardware placement against the strings and tape.
Recheck all dimensions.
Pour.
SamT
batter boards and strings. Where the strings intersect, the center of the hole happens. Use paint on ground to mark where the strings run for digging, pull strings back, dig, then reset strings to set tubes
For jsut a small storage shed like this, i would simply bury PT 4x4 posts and forget the crete
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