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How to Construct a Concrete Slab for a Grill Island

By Emily Patterson ; Updated September 21, 2017
A concrete slab provides a stable surface for an outdoor grill.

A concrete slab is a secure foundation for a grill island. Unlike a wooden deck, a concrete surface is also fireproof, and grease splatters are easier to remove with soap and water. A small concrete project, such as a concrete slab for a patio, is a small enough project for almost any homeowner to complete successfully.

Place a 2 by 4 stake in each corner of the area planned for the concrete slab for the grill island.

Tie a string to one stake and take it around the outside of each additional stake. Spray along the string line with landscaping spray paint. Remove the string.

Dig out the marked section with a shovel at least 8 inches deep.

Place a level on the soil and use a rake to reduce high spots and fill in low spots until the soil is close to level in the entire area.

Use a plate compactor to compress the soil. Start from one side and work to the other, ensuring that the entire surface has been compacted. Add 2 inches of crushed stone and use the plate compactor again. Add two more inches of crushed stone and repeat the compacting. Place the level on the compacted stone, rake down high spots and fill in low spots. Repeat compacting with the plate compactor.

Reattach the string to the corner stakes. Use a hammer to insert 2 by 2 stakes at 3 to 3½ foot intervals along the string line. The top of the stakes should be approximately 5 inches from the compacted stone, and the sides of the stakes should be lightly touching the string. Pick a starting spot and place a level across two stakes. Raise or lower a stake as needed so the top is level with the preceding stake.

Place 2 by 6 boards that have been cut according to the planned dimensions on the inside of the stakes. Attach them to the stakes with exterior galvanized screws. Attach so the top of the side of each 2 by 6 board is flush with the top of the stakes.

Lay the concrete mesh over the form and trim with heavy cutters so that the edges of the mesh maintain a consistent 2 inches from the sides of the form. Overlap sections by 2 to 3 inches as needed. Remove the trimmed pieces and note the location of each so they can be placed back in position when pouring the concrete into the form.

Mix concrete in the portable mixer. The blend is 1 part cement, 2 parts sand and 4 parts crushed stone. Slowly add water until the consistency is similar to cookie dough. Mix additional batches as needed until the form is full.

Start from one edge of the form and begin filling the form with concrete. Fill approximately half way and and place the concrete mesh sections on the concrete and then finish filling to the top of the form.

Use a long piece of wood that will span the distance between the edges of the form to pull the concrete level across the form. Use the edges of the form as rails to keep the board level. Fill in shallow spots and repeat as needed so the entire surface is completely flat and level.

Use a concrete float to smooth the top of the concrete after it is slightly firm but still wet.

Place the rounded side of the concrete edger at the intersection of the concrete pad and the form. Run it along the edge to round the edge of the concrete. Allow the concrete to cure for at least 24 hours before removing the form. Allow to completely cure for 28 days before sealing.

 

Things You Will Need

  • 2 by 4 stakes
  • String
  • Landscaping spray paint
  • Shovel
  • Rake
  • Plate compactor
  • Level
  • 2 by 6 boards
  • 2 by 2 stakes
  • Circular or hand saw
  • Hammer
  • Screwdriver (or drill with screwdriver bit)
  • Exterior galvanized screws
  • Crushed stone
  • Sand
  • Cement
  • Portable concrete mixer (optional)
  • Concrete mesh
  • Heavy cutters to trim the mesh
  • Wheelbarrow
  • Concrete float
  • Concrete edger

Tips

  • Plan this project for a day when no rain is in the forecast for at least 48 hours.
  • If the weather is very hot and dry, mist the concrete daily to slow drying so it will cure harder.

Warning

  • Rinse concrete off skin as soon as possible. It is caustic and will burn skin and eyes.

About the Author

 

Emily Patterson has been creating content for websites since 1996. She specializes in home improvement, natural body care and natural cleaning articles. Patterson holds a computing certificate from Penn State University.