Pouring a small concrete footing for a support post. Supplemental Structure:

Building A Concrete Pier
In A Basement Floor

In This Article:

A rectangular hole is cut in the basement floor, lined with thin flexible foam, and concrete is poured in. Rebar added.

Related Articles:
Skill Level: 3 (Moderate) Time Taken: 4 Hours

By , Editor


This old farm house had a problem with sagging floors, so we decided to beef up the first floor structure and add some steel lally columns in the basement. Past experience taught us that we could not simply place the column on the floor -  that the floor would probably crack and sink into the soft dirt underneath.

So we decided to cut out two small sections of the floor and pour new, reinforced pier footings.

7 inch diamond blade in a circular saw. First we laid out the position of each footing and marked the floor with a permanent marker.

Then we used the circular saw with a 7" dry-cut diamond blade. Only we cheated.  We sprinkled water on the blade with a garden sprayer, to keep the dust under control. We made sure that the saw was plugged into a Ground Fault Circuit Interrupter (GFCI) outlet, because wet power tools can give a big shock.


We can't say enough good things about this Black and Decker diamond blade. It cost about $80 five years ago, and has done a lot of cutting. The steel gradually wears down (this has lost about 1/4" off the edge).

And our old Black and Decker saw just won't die. It has seen frequent use, for over ten years, and still works fine.  Cutting concrete is abusive on a saw, because the blade tends to bind a lot and stall the saw. But this old machine takes a lot. (No, we do not receive any compensation from Black and Decker.)

Cutting edge of diamond blade for cutting concrete.


It took a lot of hammering to break up the concrete after making the cuts.
On this pier we were able to dig down about 6 inches. We lined the hole with blue sill-seal foam, just for an expansion joint.

We wanted an expansion joint so the pier would act independently from the basement floor slab. From past experience we know that this slab is thin, weak, and the soil underneath was not compacted prior to the floor being poured.

We cut two 1/2" reinforcing bars (rebar) to a length that was a little less than the diagonal measurement.


The pier next to the chimney had a small problem: there were big boulders underneath for a foundation, so we could not excavate very deep. So we made a small box from scraps of wood, to extend the hole upwards by 3". Simple concrete forms for small pier footing.


Like the other pier, we lined the hole with blue sill-seal foam. Duct tape held the foam in place while we prepared the concrete.


We mixed two 60 pound bags of Quik-Crete concrete mix in a big plastic mortar mixing tub. 

We knew that 2 bags would be enough because we measured the pier dimensions and came up with around 1/2 of a cubic foot for each. (Multiply Length x Width x Depth to get volume in cubic inches, then divide by 1728 to get volume in cubic feet.) Each 60 pound bag of concrete is very close to 1/2 of a cubic foot.

Mixing concrete from bags.

This tub also works great as a jumbo summertime outdoor dog water bowl / trough.


Placing steel rebar in concrete footing. We filled the hole about half way, spread it out, and pushed a pair of rebars just below the surface. (Rebar should be no closer than 1 inch from any edge of the concrete.)


We added more concrete...


When the form was filled with concrete, we used a small trowel to smooth the surface. Troweling surface of concrete.


Then we used a concrete edger tool to form a nice rounded edge. This helps prevent chipping of the hardened concrete.
This tool costs about $5. Well worth it for anyone who even occasionally works with concrete.


The last thing we did was to set a metal plate into the surface of the pier. This metal plate came with the steel lally columns that we will use to support the sagging floor in this old house.


We let the concrete cure for about 5 days before we applied any loads to the piers.

We raised the floor by placing a hydraulic jack next to the lally column (which went in the center, over the metal plate). This creates an off-centered load that can really stress a footing, which is one reason to add a few pieces of rebar.



Tools Used:

  • Circular Saw with Diamond Blade
  • Small Sledge Hammer
  • Cold Chisel
  • Concrete/Mortar Mixing Tub

Materials Used:

  • Foam Sill Insulation
  • Concrete Bag Mix
  • Rebar


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Written April 7, 2000
Revised January 11, 2005