How to Fasten a 4X4 Post to a Concrete Slab

Written by elizabeth arnold | 13/05/2017
How to Fasten a 4X4 Post to a Concrete Slab
Use the appropriate fasteners when attaching wood posts to concrete slabs. (Jupiterimages/ Images)

Galvanised steel brackets are commonly used to secure 4x4 wood posts to concrete slabs. These brackets are constructed of weather-resistant steel to prevent deterioration and rust. The steel brackets are available in a variety of shapes and sizes and feature prefab holes to accommodate concrete fasteners. Use masonry screws or anchor bolts when fastening wood posts to concrete slabs. To install the fasteners into concrete, use a hammer drill equipped with the appropriate masonry bit.

Determine where the 4x4 post will be set on the concrete slab and mark the spot with a pencil.

Set the galvanised steel bracket onto the concrete slab at the indicated mark. Square the bracket to the desired angle and make pencil marks on the concrete slab through the prefab holes on the bracket.

Drill the appropriate holes depending on the type and how many fasteners you are using. Follow the fastener package specifications regarding the diameter of the hammer drill's masonry bit. Clean the holes by sliding the spinning masonry bit up and down to remove any debris.

Position the bracket over the holes you've drilled and insert the fasteners through the holes and into the concrete slab. Tighten the fasteners with the specified tool.

Place the 4x4 post into the bracket. Plumb the post by placing a level on the outside edges and checking the bubble. Insert wood fasteners into the 4x4 through the prefab holes located around the bracket, and tighten them with the manufacturer-specified tool.


Wear safety goggles when using a drill to avoid eye injury.

Tips and warnings

  • Wear safety goggles when using a drill to avoid eye injury.

Things you need

  • Tape measure
  • Pencil
  • Post bracket
  • Hammer drill
  • Masonry bit
  • Concrete fasteners or anchors
  • 4x4 post
  • Level
  • Wood fasteners
  • Appropriate tool to tighten fasteners

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