How to Build a Deck Over a Concrete Patio

Placing a deck over the top of a patio avoids the need to tear up the existing concrete.

Instead of removing a concrete patio before building a deck, it is possible to simply place a deck over the top. This allows you to avoid having to deal with the task of breakup and removal of the concrete, and eliminates the need to place crushed stone under the deck to help against erosion. Also, setting the deck posts into the ground and against the edge of the concrete gives the posts added support.

Things You'll Need

• Tape measure
• Stakes
• String line
• Spray paint
• Post hole digger
• 4x4 deck posts
• Gravel
• Concrete mix
• Large bucket
• Level
• Shovel
• Drill and bits
• 3/4-inch lag bolts
• 2x6 frame boards
• Metal joist hangers
• Hammer
• 1x6 deck boards
• 2-inch deck screws

Instructions

1. Measure the length and width dimensions of the concrete patio with a tape measure. Measure out from the concrete an additional 8 inches all along the perimeter and mark the outline with stakes and a string line.

2. Place a spray paint mark on the ground at each corner to designate the location of a support post. Place another mark on the ground across the perimeter every 4 to 8 feet depending on the length of the deck.

3. Dig holes at each paint mark using a post hole digger. Make the holes 12 inches deep and 8 inches wide, and position them tight up against the concrete edge. Place a small layer of gravel in the bottom of each hole.

4. Mix concrete in a large bucket. Place a 4x4 post in the hole and check it for straightness and vertical level. Pour more gravel in the hole to fill it half full. Verify the level and post position. When satisfied, fill the remainder of the hole with concrete using a shovel. Allow the concrete around the posts to dry for 24 hours before continuing.

5. Mark the height of the deck on the posts and on the house. Drill holes for 3/4-inch lag bolts through the posts and the house floor frame. Anchor a 2x6 board securely against the house using the bolts, and then build an outer frame perimeter mounted to the predrilled post holes with the same sized bolts.

6. Install metal joist hangers every 16 inches across the frame, parallel to the board mounted to the house. Hammer the hangers down securely to avoid them moving during construction. Place 2x6 joist boards into the hangers and hammer nails through the metal frames to keep them tight.

7. Lay 1x6 deck boards across the frame and over the joists starting at the edge of the deck furthest from the house. Anchor them into the joists using two 2-inch deck screws per joist. Tighten the boards up against each other to allow for shrinkage of the wood that will create the gap seen in most decks.

Tips & Warnings

• Use treated lumber to help protect the wood from the elements and extend the life of the deck.

• Don't leave a gap between boards or shrinkage will make the gap expand too far.

• Use caution when working with power tools to avoid accidental injury.

References

• "Building a Deck: Expert Advice From Start to Finish"; Scott Schuttner; 2002
• "Complete Deck Book: Everything You Need to Design and Build Your Own Dream Deck"; Steve Cory; 2007