When you set a lamp post with anchor bolts into concrete, it is a two stage process. First you must set the anchor bolts and then pour the concrete around them, and then you will set your post onto the bolts as they will protrude from the concrete base. Setting anchor bolts into concrete is an activity that requires a great deal of concentration and precise measurement. As frightening as that sounds, the process is doable and ultimately requires that you are willing to check and double check your measurements before the concrete is poured. Anchor bolts that are set incorrectly will not allow you to stand and connect your lamp post safely.
Begin by measuring the base plate of your lamp post where your bolts will be attached. Transfer those measurements to a piece of plywood and cut out the shape. This will be your bolt template
Measure the centres of each bolt hole and transfer those measurements to your bolt template. Use a drill and paddle bit (sized to match the diameter of your anchor bolts) to drill out the bolt holes. Typically, the base of a lamp post is square with four bolt holes; your template should be an exact matching square with four drilled holes. Hold your template up to the base plate and it should match exactly.
Consult your blueprints for the exact centre location of the base plate of the lamp post in the concrete form you are about to pour. Typically, base plates are put onto piers; a pier may be separate from all other structures or be built into the wall. Your prints will show you the exact location of the centre.
Locate the centre of the base plate in the actual form. Most often you will have to mark the centre points on the sides of the form, then set a nail into each of these points and connect them with string to create a cross. The centre of the cross represents the centre of the base plate.
Measure out from the side marks of your form to where the centre of the bolts are in relation to it on two opposite sides. For example, if on the north face of the form you have a centre mark and you know that the centre of your bolts is 4" from the centre of the base plate, you will place two marks on the north face of the form, one 4" to one side of the centre mark and one 4" to the opposite side (i.e., the south face). Duplicate these marks on the opposite face of the form.
Cut two pieces of 2x4 the exact width (from inside face to inside face) of your form between the two faces that you marked in Step 5.
Nail the 2x4s in place between the two marked sides of the form. Make sure that the 2x4s are turned on their edge and that they are placed so they run between the two centres of your bolts but will not hit the width of the bolt. For example, if your bolt is 1" in diameter and the centre of the bolt is 4" away from the centre mark of the base plate, then you want the outside edge of your 2x4 to be 3-1/2" from the centre mark of the base plate. Make sure that the top of each 2x4 is set to the top of the grade of the base plate. Check your blueprints for the correct grade. Grade is another term for "height from the ground (or the point used as reference on site)." Nail both 2x4s in place.
Lay your bolt template on top of the 2x4s and under the string cross. Center the bolt pattern on the centre of the string cross and nail it in place to the 2x4s.
Place the anchor bolts through the holes in the bolt template with the "foot" of the anchor bolt in the concrete. Anchor bolts are typically shaped like an "L" with the bottom part of the "L" shape being referred to as the "foot." Pull the anchor bolt up and spin the nut onto the base of the thread. Carefully wrap the entire portion of the anchor bolt (and nut) above the template with duct tape to prevent any concrete from fouling the threads.
Pour your concrete. Once it has cured, remove the forms (including the bolt template) and take off the nuts. Lift your lamp post and lower it onto the bolts. Tighten the nuts into place to complete installation of your lamp post.
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- If your concrete was poured without anchor bolts and it is acceptable to the inspector, you can drill and epoxy straight anchor bolts to hold your lamp post. Make your bolt template and locate the centre of the base plate on the concrete. Center the bolt template over that and mark where your bolts need to be. Use a hammer drill to drill out to the required depth. Clean the hole and fill with epoxy and set your straight anchor bolts. Once the epoxy has cured, stand your lamp post on the bolts and tighten the nuts on to hold it in place.
- It is very important that you go back after the concrete is poured and before it has hardened to check that your anchor bolts are rising straight out of the concrete. If they are not, you will be able to straighten them then but not after the concrete has cured. Anchor bolts that are crooked will not fit your base plate nor can they be straightened with a sledge hammer. You will not be able to install your lamp post on the anchor bolts without repairing the bolts, which will involve expensive reconstruction.