Drainage Ideas for Flagstone Patios
A flagstone patio is a common addition to a home. Some are freestanding, meaning the flagstones are laid next to each other without grout or sealer. Only sand or a soft mortar is used to hold them in place. In this case, water will drain directly through the tiles and into the ground in most cases. For flagstone patios that have mortared grout, more in-depth preparations need to be made to ensure the patio will drain. Does this Spark an idea?
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Pitch It
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The first thing to do when building a flagstone patio is to induce a pitch in the layout. This means that one end of the patio is higher than the other. This pitch creates drainage because water naturally flows to the lowest point due to gravity. To pitch a patio you simply grade the area where the flagstones are going to be installed so the ground slopes at a rate of around ½ inch per yard. Then lay the mortar and flagstone onto the pitched ground and seal your patio. Place the higher end nearer to the house and the lower end closest to the area where you want water to drain.
Bevel Pitch
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Another idea is to include a bevel pitch in the patio. This is ideal for very large patios and when you want to have a completely flat surface. This involves creating a bevel area around the edge of the flagstone patio on all four sides where the tiles slope at a gradual pitch of ½ inch per yard (or whatever rate suits your installation). This allows water to drain off all four sides of the patio and it gives you a completely flat area in the center. You can also bevel pitch the entire patio, by starting from the center and beveling each side from that point. The result is a very shallow pyramid shape. This is ideal for areas that need a lot of draining and do not need to have the water drained in one direction.
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Drain Pipes
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Installing a drain pipe is another idea. This can be installed in any patio, whether it is mortar sealed or not. The patio still must be graded, however, and the grading must lead toward the mouth of the drainage pipe. Dig a drainage ditch and insert the pipe into the ditch. Use a 2-inch PVC pipe. Install it in the ground so the mouth of the pipe will be level with the flagstone tiles once the patio is finished. Then mortar around the pipe and seal the edges. The pipe can be placed at the edge of the patio or in the center.
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