DIY Network

How to Replace a Concrete Porch

If settling has caused a concrete-slab porch to crack and fail, follow these steps to remove and replace it.

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steps can be taken to correct a settled porch
  • Time

    Two Days

  • Price Range

    $250 - $500

  • Difficulty

    Hard

Highlights:

Step 1: Demolish the Old Porch

If there is a roof over the concrete porch, install temporary supports to secure it before starting this project. Once it's definitely secure, you can remove the permanent posts that support the roof.

Break up the old porch using a rented 120-lb compressed-air jackhammer with bull-point bit, or use a sledgehammer. Start at the outer edge of the porch and work inward toward the house. Work in a back and forth motion taking care to avoid damaging the foundation of the house.

a compressed air jackhammer breaks up old porch

Step 2: Prepare the Site

Remove large debris from area. Compact the small gravel that remains with a rented power tamp or hand tamper (Image 1). Mark out the placement of the new porch and drive stakes at each corner. Create a concrete form by attaching 2" x 4" or 2" x 6" boards (depending on desired thickness of porch) to the corner stakes (Image 2). Drive supporting stakes every 3' along the outside of the form.

Make sure the forms are level and plumb. However, the entire form should slope away from the house 1/8" for every foot of width. Make sure all the form joints are tight and that the form is sturdy enough to hold the concrete.

Pour approximately 3” of gravel into the form and spread it evenly over the entire area. Smooth with a garden rake and then tamp down with hand tamper. Lay wire reinforcing mesh over the entire area, elevating it slightly on small rocks. Make sure the mesh sits at least 2" below the top of the form.

Step 3: Pour and Finish Concrete

For small jobs, you can use pre-mixed concrete and make it on-site. For larger jobs, it might make sense to hire a concrete delivery service.

Pour enough concrete to fill the form completely. Smooth with garden rake as you go to eliminate bubbles and level the surface. Finish smoothing with a trowel and concrete float.

Allow the concrete to harden for approximately half an hour depending on the conditions. Run a concrete edger between the concrete and the wooden form. Texture the surface by lightly brushing with a broom.

Be sure to keep the concrete covered with plastic as it cures to prevent cracking and create the hardest possible finish. Allow the concrete to cure completely -- anywhere from 24-48 hours to 5 days or more, depending upon the volume.

quickly smooth concrete with a smooth trowel

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