Timber decks refresh the look and feel of a landscape and they feel softer to the touch than concrete patios. Replacing a concrete patio with a timber deck is expensive and involves a lot of labour. As an alternative, you can build the deck over the concrete patio, using it as the foundation. This is a convenient and cost-effective way to build a new surface without letting an existing one go to waste, and you won't have to worry about weeds developing beneath.
Building the Frame
Use 2-by-12-inch boards to build the frame and supports for the deck. Measure the dimensions of the patio and set two boards aside for the front and back and two boards for the sides of the deck frame. Cut the four frame boards down to the length and width of the patio. Cut enough support boards to space them 1 foot apart along the length of the patio and make them 4 inches shorter than the patio width. If you plan to stain the timbers, it's easier to apply the stain before the boards are assembled.
Setting the Piers
The concrete patio beneath your timber deck will provide a strong foundation. Once you cut and stain all of your frame and support boards, you can set them on piers. Concrete block piers are preformed to support decking frame boards on a level surface. They come in different sizes, typically raising the deck 1 to 2 feet from the ground. Arrange the piers in rows across the length of the patio, spaced a foot apart, and in the corners for the frame boards. Place the supports on the back piers first, perpendicular to the front and back. Set the frame boards at each side so the front and back boards touch the ends of the supports.
Pressure-treated or naturally rot-resistant boards are the most practical choice for a deck because they don't rot. Wear a mask and gloves when handling pressure-treated wood and do not burn the wood because the chemicals it contains are harmful. Use 2-by-4- inch boards for the surface decking and set them parallel to the front of the patio. You can place a nail between each board to space them evenly apart if you're using cedar.
Avoid spacing pressure-treated timbers because they shrink over time, creating small gaps between the boards. Use two 2 ½- inch galvanised screws to secure the surface boards to the frames and supports every place where they overlap.
Covered by timbers, there's little maintenance you'll need to do to the concrete surface. Consider sealing it with a penetrating sealant to fill the pores and prevent water damage. Fill cracks and pits with a concrete patching compound before setting the timber deck. You can prevent the clearance between the deck and concrete from becoming an eyesore by attaching lattice between the deck frame and the concrete.