A brick patio that was improperly laid or has insufficient support can sink or sag over time. Even a properly laid patio can begin to sink after many years of use. Fortunately, you can repair a sunken brick patio with relatively few tools and materials. This is a task that most homeowners can complete over the course of a weekend.
Remove all of the bricks in the sunken area of the patio, except for the cut bricks along the edges. Using a piece of chalk, number each of the cut bricks along the edges. This will allow you to put each of the cut bricks back in the same spot. Otherwise, they might not fit when you put the patio back together. Stack the numbered cut bricks in order away from your work area. This will make rebuilding the patio a quicker process.
Check for clay or soft soil around the edge of the patio. Clear out as much soft soil as possible. Left in place, it could cause sagging in the future.
Assuming only part of the pation has sagged, span a 1-inch by 2-inch board from the edge of the remaining bricks to the edge of the excavated area. This will show the finished height of the patio.
Fill in the excavated area of the patio with limestone pea gravel to a depth of three inches below the finished height. Use a tamper to pack and level the gravel. Be sure to fill in any areas of soft soil you have removed around the edges.
Pour one inch of construction grade sand over the pea gravel. Use a tamper to pack and level the sand. Carefully replace the patio bricks, making sure they fit tightly together. Tap each brick level with a rubber mallet. Replace the numbered cut bricks along the edges in order.
Pour fine grade sand over the patio and use a broom to sweep sand into the joints between the bricks. Spray the patio down with a garden hose to allow the sand to settle. When the patio is dry, pour and sweep sand into the joints again.