When adding a patio to your home landscape, plan for patio drainage before you begin construction. Proper drainage will prevent tipping, shifting and post-frost heaving of your patio, and will keep water from seeping into your basement. When done correctly this sloping procedure will be invisible, but will prolong the stability of your patio and your foundation. Follow these directions to incorporate patio slope for drainage into your new patio.
Determine Where You Want Your Patio
If your patio will be laid in contact with the basement wall, be sure to construct it with a slope of ½ inch to each 9 linear feet that it extends from the wall. This will suffice to help your patio drain off precipitation. In areas where the ground freezes deeply, it will also prevent frost heaving the patio stones in the spring. If you want the patio more than 3 feet away from the house, study the existing grade of the lawn. If the lawn is nearly flat, use the slope rule above to create an adequate drainage slope away from the house. If the lawn is already sloping, follow the natural grade when building your patio. On a steeply sloped lawn, create a multi-level terraced patio to prevent soil erosion and to keep the patio structure intact. Retain any existing shade trees, and plan for future landscaping such as gardening containers or a privacy hedge.
Measure the Patio and Purchase Materials
Dig up and excavate the area where you will lay the patio, to 4 inches below the grade. You will add sand and gravel here to stabilize the patio, provide water drainage and stop weed and grass growth. You will need to buy gravel in cubic yards, so multiply the cubic footage of the areas to be covered by 0.037 to work out how much gravel to buy. Dry silicon sand comes in bags of 55 lbs. capacity, and each covers about 125 to 150 square feet. Add several cubic yards of limestone to the base soil. Buy the limestone according to the formula above. To obtain the correct number of patio stones, divide the square footage of your patio by the area of one patio stone.
Prepare the Ground and Lay the Patio
Prepare the ground so it will stay level while allowing for drainage. Put in the gravel first, and level it with a rake. Pour in the limestone and spread it out evenly over the gravel. Lastly, add the silicon sand. If you choose polymeric sand, which inhibits weed growth more effectively, you will need several 10-lb. bags. Each covers about 30 square feet of ground. Save one bag to fill between the stones.
Place the Patio Stones Snugly
Lay in the patio stones as closely together as possible. Tap the edges with a rubber mallet to settle them tightly. Sprinkle one bag of polymeric sand or ¼ bag of silicon sand over the patio stones, sweeping it into the cracks till they are full. Compress soil around the edges of the patio, and lay new turf as needed.