How to Build Post Supports for a Porch

Mark the location of the post supports on the ground with spray paint.

Dig a trench along each line of supports with a 1.5-ton excavator. Dig beneath the frost line to protect the post supports from shifting when the ground shifts as it freezes and thaws. Your local zoning board can tell you how deep the front line is in your area.

Insert wax fiber tubes into plastic footings. The tubes are a form for the concrete that will be poured, and the footings spread the concrete at the bottom of the support out over a wider area. This helps prevent the posts from sinking into the ground.

Place the forms into position inside the trenches. Have them inspected if local building codes require it.

Backfill the trenches around the forms. Check the support forms for level (horizontally straight) and plumb (vertically straight) as you fill the trenches with the dirt.

Insert footings upside-down into the top of the waxed fiber tubes. The footings will serve as a funnel when the concrete is being poured into the forms.

Fill the forms for the post supports with concrete. Depending on how deep the post supports extend into the ground, and how many supports you have, you may want to hire a concrete contractor. Stir a shovel inside the forms as you add concrete every 8 to 10 inches to free any air bubbles trapped inside.

Take the footings off the waxed fiber tubes.

Drag a trowel across the concrete along the top of the waxed fiber tube to smooth it.

Install the hardware for the posts into the concrete. This usually involves placing J-bolts or anchors into the concrete and allowing the concrete to harden around them, but it can vary by the type of hardware you're using to attach the wooden posts to the concrete piers. Allow the concrete to set for at least four to five days.

Remove the waxed fiber tubing that extends above the ground by cutting it away with a utility knife, if desired.