Saturday, March 8, 2014

Bolt A Post Base To A Concrete Pad

Post bases anchor your wooden supports into concrete footings.

A post base attaches 4-by-4 posts to concrete for structural members to support a roof or a deck on footings. An anchor bolt attaches the bottom of a post base into the concrete and expands as a molly bolt does in a wall to hold the post base firmly in place. The bottom of each wooden post sits on a platform to keep the wood dry and discourage rotting. A do-it-yourself homeowner can install post bases properly with common tools.


1. Measure the post locations on the concrete pad with a measuring tape. Mark the center of each 4-by-4 post with a carpenter's pencil.

2. Place a post base over the center mark and trace inside the center hole for the anchor bolt. Remove the post base.

3. Place a drill bit in a drill in the same diameter as the anchor bolt that is supplied with the post base. Measure the length of the anchor bolt. Center the drill on your mark for the anchor bolt and drill a hole ½ to 1 inch less than the anchor bolt length.

4. Clean the concrete debris out of the hole with a shop vacuum.

5. Place the anchor bolt in the hole. Insert the post base over the anchor and slide the adjustment nut on it. Turn the anchor bolt clockwise about four revolutions to fasten it into the concrete.

6. Place a level on the post base top and side to level the base both vertically and horizontally. The base will slide in any direction to move it so the base is plumb. Tighten the adjustment nut with a pair of adjustable pliers.

7. Place the flat cover over the base. Set a 4-by-4 post into the base.

8. Hold the post steady in one hand and drill a pilot hole in each side of the screw holes in the post base. Insert a 3 ½-inch stainless steel screw into each of the two holes and drive them in with the drill.

Tips Warnings

Use stainless steel screws and post bases because they will not rust and make a long-lasting project.

You can attach a post base on a new concrete slab by marking the post centers and placing the anchor bolts in position, then pouring the concrete around them. This method does not require drilling a hole in the concrete.

Post bases are available at home improvement centers and hardware stores.

Tags: bolt, post, base, concrete, post base, anchor bolt, into concrete, 4-by-4 post, base over, post base over, post bases