How to Install J Bolts in Concrete

Before pouring concrete you must set in place anchor bolts for your walls, columns or machinery that will be installed on top of your pour. Anchor bolts are J-shaped; the foot of the "J" allows the bolt to anchor itself into the concrete and keep it from sliding out from the weight and tension of what it is holding in place.

1. Read your project plans to determine the spacing and location of your anchor bolts. If you are preparing to pour the foundation support for a wood framed wall, look for the spacing for a line of J bolts that the sill plate of the wall will be attached to. If you are going to be standing columns or metal framed walls, or bolting machinery or tanks in place on top of a slab, look for the anchor plate locations on the plans.

2. Measure and cut several 2 by 4s so that they can span across the concrete forms. Nail these pieces into place but make sure they are high enough to remain above the level of your concrete pour.

3. Measure and mark the location of the J bolts to be installed. (For a wall support, the mark will typically fall in the center of the form.) Mark the support 2 by 4s and skip to Step 5. For an anchor plate support, go to Step 4.

4. Mark the center of the bolts on your plywood bolt template. (Your bolt template is a piece of wood that is the exact size of the anchor plate of the base of the column or machinery that will be installed on the bolts later.) Mark the center of the bolts on the template and drill bolt holes with a drill and paddle bit. Nail the template onto your 2x4 supports so the center of the template matches the center of the anchor plate that will be placed later. (You will find the center locations on your project plan.) When finished, go to Step 6.

5. Make a mark that is offset from the center of your bolts 1/2 the diameter of the J bolt you will be installing. Nail a long 2 by 4 across the support 2 by 4s so that one edge is lined up on this offset mark.

6. Set your J bolts in your templates. For a wall template, tie the J bolt to the long 2 by 4 at the required spacing for your sill plate. Use tie wire and Linesman pliers to attach the bolt to the 2 by 4. Make sure that the J bolt extends deep enough in the pour to meet your project depth guidelines. For a bolt template, pass the bolt through the holes in the plywood and spin a nut on each bolt to suspend it in the concrete. Check that the bolt extends into the concrete for the required depth.

7. Wrap the threads of each bolt with duct tape. (This will prevent concrete from filling the threads and making it difficult to get the nuts on or off later.)

Tip

Check your bolt templates immediately after filling your forms with concrete. Make any adjustments necessary to bring the bolts back into place; the force of the concrete will move them.

Warning

Don't rely on "floating" a bolt into concrete to set it properly. A bolt that is hand set in concrete with no support will sink or set at an angle that will make it unusable later.