Before You Begin
Determine the direction of the slope and how you will use it before drawing any plans. Yards sloping toward your house will need retaining walls to keep the earth from filling back in after you dig, due to pressure from rain and snow runoff.
Yards sloping down and away from your house will require leveling with building materials, rocks or fill dirt before installing the patio.
Elevate the patio if it will be attached to a second story by using railroad ties and corner support sunk in cement. The slope of the yard will not matter as much in this case, as each railroad tie will need to be placed in a hole so that they are level at the top.
Dig the post holes for the railroad ties to the depth required by local building codes. Most codes require post holes to be below the frost line in your area.
Slope Towards House
Measure and mark the patio area for a yard that slopes toward your house using red spray paint. Red spray paint shows up well against grass, dirt, sand and rocks.
Dig out the area with a backhoe, which you can rent from your local home supply store. This will leave you with a flat area, ready to frame and a wall of dirt around the flat area.
Lay out landscaping timbers along the dig line to the height of the slope before digging. Secure the timbers in the ground with 12-inch nails, hammered into the middle and each end of the landscaping timbers.
Add more timbers on top of the first row, and attach to the previous row with the 12-inch nails and the hammer. Add enough timbers to create a wall that is level with the ground and surrounds the patio where necessary.
Back fill behind the wall with the dirt you took out of the area until there is no gap between the retaining wall and the dirt wall. Reseed the grass at the top of the retaining wall or add decorative mulch to the area.
Frame the flat area you cleared out for the patio with two-by-four pieces of plywood. Add gravel or sand to level the area before pouring concrete or laying brick pavers.
Slope Away from House
Dig out the area for your patio that slopes away from your house with a backhoe.
Use a post-hole digger to dig enough holes to support the patio to a depth indicated by local building codes. Fill each hole with quick dry cement, and add enough water to make a thick paste.
Insert the railroad ties into the cement and let them cure according to package directions.
Trim each railroad tie after the cement dries to the appropriate height needed for the patio on the sloping yard. Frame the patio around the support posts and finish with pressure-treated deck lumber.
Fill in the area underneath the patio with gravel or sand before securing the deck boards.