Drainage And A Patio Seatwall
About four years ago I poured a concrete patio that is 12'x30' and slopes away from the house about 2 and a half inches. I ran tile down the edge of it for drainage that is also connected to a downspout. I was wanting to build a sitting wall along the edge of the patio but don't know what to do with the tile around the patio. I have enough fall to bury it lower and place the sitting wall above it but with the frost in the winter I'm worried the wall will heave. So I was wondering if I should move the tile on the lawn side of the sitting wall and leave a few gaps in the wall or leave the tile under the base stone of the wall. I'm most concerned with the drainage and stability of the sitting wall during the freeze/thaw cycle. Any ideas would be greatly appreciated.ANSWER
The way I see it, you have three things to consider...the patio, the drainage pipe and the wall. If I were designing a patio with a seatwall at the far edge, I would include a trench drain at the base of the wall. This would collect the water draining off the patio before it hit the wall.
We probably think of a seat wall as being built on a patio, but there is no reason it cannot stand alone if built correctly. Therefore, I believe you can build your seatwall adjacent to the far edge of the drain. I am not sure what type of "drainage tile" you have, but a trench drain is typically narrow and is unobtrusive.
So you now have your patio, the drain, and then the seatwall. Whether you keep your drain as is or change it to a trench drain depends on what is currently there. A trench drain can still connect with your downspouts.
You want your drainage BEFORE the wall. And I would not place drainage UNDER a wall.
Hope this helped.
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