After a year or so of every kind of delay imaginable I finally got a concrete pad poured to erect my 30 x 50 Olympia steel building on. To my delight the concrete guys did not square up the pad correctly.
How do I go about correcting this? The pad is a 30' x 50' monolithic pour with a 1.5" x 1.5" sheeting edge all the way around. We decided to drill and epoxy the anchors instead of having them set in the pad itself so we would have a little flexibility. The 50 foot side measurements are OK so we went ahead and set the red iron columns in the middle at the 25 foot mark. How do we proceed to get the 4 corner columns square when the both of the 30 foot dimensions are off? Attached is a pic of the dimensions.
Thanks
The best way is to put up batter boards. You don't need to worry about having the lines on grade because you already have the pad poured and hopefully it is at the planned finish grade. Once you have the batter board corners up you can take a framing sq at one corner, pick any it doesn't matter
at this point. start by laying the framing sq down on the concrete about 1 ft in either direction from one of the corners of the concrete pad. lay it down so that it forms an angle and looking down both directions to make sure you are not going to run out of concrete at the other end and adjust the square one way or another until both of your eyeball lines are on the concrete all the way to the other corner of the pad.
With the framing sq still laying on the pad stand behind your batter board and eyeball down the edge of the sq and place a small nail in one side of the batter board that is in line with the framing sq. Do the same in the other direction this doesn't have to be perfect you are just looking for a starting point to make sure the building will fit on the pad.
Pull strings from each of these nails you have placed in the first batter board to the batter board in the opposite direction. It is easier if you have someone helping at this point, someone to move the string one way or the other while you look down the first line to keep about the same amount of distance from the outside edge of the concrete pad then put another nail in that batter board and tie the line to it. It still doesn't have to be perfect at this point.
Do the same thing the the line in the other direction, eyeball down holding the sq so that this line lines up down the edge of the framing sq while holding the other edge of the sq on the first line you pulled. Put a nail in that board where it lines up and tie that string off to the nail.
You now should have strings pulled down two sides of your pad and where these two lines intersect is your first corner. Next you want to check to make sure these two lines are actually sq and to do this you use the 3/4/5 method and you need two people here also. From the point where your two lines intersect measure down one line 3' and mark the spot with a felt pen and measure down the other line 4' and mark that spot also. To be a perfect sq the distance between these to marks needs to be 5'. If it isn't you need to adjust one line or the other until the distance between the two marks is 5'. Once it is you now have your first corner point squared and you move on to the next corner.
Once these two first lines are in and squared don't move these again put a good nail in all three points and pull these strings good and tight and recheck for squareness. Measure down from each of these strings and mark the string at the distance that corresponds to the building dimension in that direction or to the distance to the outside corner of the corner post in each direction.
Now you are back to eyeballing again. Go to the left batter board from the square point and pull a string to the far corner and put a nail in the board to tie the string to, anywhere at this point. Then measure down that string the distance it should be to the far corner post and put a mark on the string where the corner needs to be. Also when pulling these strings try to pull them all to the same amount of tension because the marks will change somewhat if one is pulled tight and the next is not.
Next move over to the right line and do the same thing. eyeball a line that way and put a nail in that batter board then pull another string to the far corner then measure from the first line to the distance it should be to the far corner post in that direction and mark the string. Now that the second set of strings are marked move these two lines up or down the batter board to the point where the two marks intersect and drive a new nail and tie off both strings with the two marks as close as possible.
Your walls should be pretty close to sq all the way around but you have to check them to be sure. If you were lucky and you did in fact end up with all the corners sq more power to ya. To check this you need a tape long enough to go from one corner to the far corner and measure the distance and write it down. Then go to the other two corners and measure from there and these two points should be exactly the same distance. If they are not you need to adjust your lines until they do.
As stated before don't move the first two lines you put in. I always try to start with the front right hand corner to establish my first sq point and when doing my adjustments I move to the right or to the back right hand corner and check that corner using the 3/4/5 method again remembering not to move the original square line but if adjustments are needed move the back wall line to bring it into sq. keep in mind that 1/4 of an inch in 4 feet is a lot on the other end so measure as close as you can but remember it is almost impossible to get it perfect. Once the lines are adjusted check the diagonals again and try to get both measurements to within 1/4 of an inch or there about. You have room for play even if you can't get them within a half inch but it is best to get these two measurements as close as possible because things will go better as you progress.
