How to Extend a Floating Deck Over a Cement Porch

A floating deck is a deck that stands independently and is not connected to the house in any way. Usually, a deck structure is supported by footers, which are deep piers of concrete upon which the deck posts rest. To extend a deck over an existing cement porch, you can skip the arduous construction of footings and place the deck on top of wooden sleepers secured to the cement slab with special masonry anchors. Most cement porches are constructed several inches lower than the exit door threshhold, so a floating deck should fit nicely. If the vertical distance between the door threshhold and the cement porch is less than 3 inches, however, you will need to remove the cement slab; otherwise the finished deck floor will rise too high and interfere with the opening and closing of the door.

Tapcon screws
Screw gun
Pressure-treated 2-by-4-inch boards
Water sealer
Paintbrush
Level
Deck plank boards
Hammer
2 1/2-inch 10d galvanized nails

Instructions

- 1
  Measure the length and width of the cement porch slab. Cut pressure-treated 2-by-4-inch boards to run perpendicular to the house wall. These boards are called "sleepers" and serve as the foundation of your deck. Paint water sealer over the boards to protect them from moisture and prevent rot.
- 2
  Lay the sleepers onto the cement slab. Fit a sleeper on each end of the slab, and put additional sleepers every 16 to 23 inches across the slab.
- 3
  Place a level across the sleepers to ensure they are level. Slip small plastic shims or shims of wood sealed with sealer to level each sleeper.
- 4
  Affix the sleepers to the slab with Tapcon screws. These screws are specially made to pierce through hard cement.
- 5
  Place the first decking plank on the sleepers nearest the house wall, perpendicular to the sleepers. Adjust the first plank so it is flush with the house wall. Lay the plank so it overhangs the sleepers on each end and both sides of the cement slab by 1 inch. Mark the overhang with your pencil. Cut the plank and place it back against the house. Nail the plank into the sleepers using 2 1/2-inch, 10d galvanized nails.
- 6
  Place the next plank on top of the sleepers in front of the first plank. Allow a narrow, 1/8-inch space between the two planks. Allow the board to overhang both sides of the cement slab. Do not cut this plank to fit; you will trim all planks with a circular saw after you have installed the entire deck. This will ensure uniformity for both sides. Nail the plank into place.
- 7
  Continue installing planks onto the sleepers, allowing a 1/8-inch space between planks and allowing an overhang of 3 to 4 inches that you will trim off later.
- 8
  Snap a chalkline on the right and left sides of the planks, to create an 1-inch overhang on both sides of the cement slab. Saw the planks on the chalk lines with a circular saw.
- 9
  Measure the length of the three outer sides of the deck for a skirtboard. The skirtboard consists of deck planks nailed around the edges of the deck platform, and it creates a finished appearance. Cut the planks to fit and nail them to the edges of the deck board planks.
- 10
  Seal the planks with water sealer to protect the wood from moisture and rot.

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