sweetverve

Drainage for paver patio - conundrum!

sweetverve
15 days ago
last modified: 15 days ago

Our house's downspouts connect to underground gutters which go to the city's storm drains. The underground gutters are old and broken and need to be replaced. Conveniently, they are located under our concrete patio, so that needs to be ripped out in order for the repairs to take place. We plan to replace the patio with pavers instead of concrete. Having spoken to four landscape professionals, we've received four different plans as to how to address the drainage of the patio.

Behold my artistic rendering of our backyard :)

The patio is in purple. The backyard patio connects to two walkways along the sides of the house. Surrounding the patio are garden beds with shrubs and trees, as well as our lawn. The rear of the yard (north side) backs up to a steep uphill. The blue circles on the house represent the downspouts which connect to underground drain pipes. The gray square adjacent to the house is a step from a doorway leading to the back yard.




backyard looking west to east



backyard looking east to west



looking at the back of the house from the patio



The conundrum facing us is this: how to slope the new paver patio at the rear of the house to allow for proper drainage?

- If we slope it down from the house at a grade of 2%, then at the spot where the pavers meet the lawn or the garden beds, the pavers will be 4-6 inches below grade.

- One landscaper suggested to put area drains throughout the paver area, thus the pavers will be sloped toward the drains. This will keep the edges of the patio flush with the surrounding lawn and garden beds. We would put one drain in the center of the large patio area (on the west side), and two in the smaller area (on the east side). I am concerned these drains will make the patio feel too "bumpy" and indented. I can't seem to find any photos anywhere where there are so many drains close to each other.

- Another landscaper suggested putting a channel drain along the rear wall of the house, and sloping the patio down towards the house. That seems like the most counter-intuitive option and frankly is my least favorite.

- Each landscaper also had several french drain options all over the yard, but as each of them carries a ~$10k price tag, I'd like to be sure they're necessary before agreeing to them.

- The current concrete patio was put in by the previous owners, and has a slope down going west to east. No slope at all going south to north. Because of tree roots/ground settling/etc, the concrete has shifted over time and this slope has been disturbed and does not actually carry the water away from the house. But maybe this is the way to go when we put in pavers? Just slope it along the house instead of away?


Any ideas or suggestions are welcome!

Comments (7)

  • PRO
    Yardvaark
    13 days ago
    last modified: 13 days ago

    In the drainage/grading scheme I presented, don't just look at what the patio is doing (which is why I left it out) ... look at what the whole yard is doing. From the back 'fence'/hill, the yard is sloping down toward the house. At the house, it's sloping down toward the back lot line. But there are no abruptly mismatched abutting edges where the opposing slopes meet. If you envision the yard surface as covered in a warm, smooth slice of Velveeta cheese, it would have a slight sag on account of the two opposing directions of slope and they would meet where I show a light blue dashed line. Where they meet would not be a crease, but a smooth, gradual transition ... like one might observe in a piece of plywood that wasn't nailed down, in a humid environment. Regardless of where your patio or occurs or to what expanse it extends ... it matches exactly the previously described yard surface, as it is inlaid into it.


    sweetverve thanked Yardvaark
    Best Answer
  • PRO
    Yardvaark
    14 days ago

    Confirm that the yard backs up to a hill that is going up or down. (I only see blackness/plant shadows.) Confirm that the overall drainage of the lot goes from front to back or back to front. If drainage of the lot goes toward the front, show a picture of front yard and house taken from the street.

    I would never pitch grade toward house expecting to collect the water in a slot drain!

    I'm an advocate of above ground drainage if it is at all possible because it is trouble free as compared to underground pipes. You should also check with city engineering department to see if they allow connecting residential drainage to city storm drains. In many or most places, it is not allowed. Cities want as much water as possible to soak into the ground instead of entering (and overwhelming) the city storm drainage system.

    sweetverve thanked Yardvaark
  • sweetverve
    Original Author
    14 days ago

    The yard does back up to a hill going up, see the photo below. At the top of the hill is another yard. We have not ever had issues with water running down the hill, even during heavy rains.


    Starting at the fence, the yard is mostly level, with no obvious grade to it.

    At the front of the house, the lot slopes down to the street, see photo below.

    We have considered for the underground gutter pipes to terminate in a "pop-up" drain at the top of this slope, rather than continue underground to the storm drains. Underground gutters seem to be the norm in this neighborhood - when I said that they connect to the city drains, what I meant was the they continue underground under the sidewalk, and come out on the curb, where the water drains into a groove on the side of the road (sort of visible in the above photo). The street is on a slope, so all the runoff goes into the storm drain at the bottom of the hill.

  • PRO
    Yardvaark
    13 days ago

    The drainage would flow generally like this ...


    (Dashed line is greatest concentration of flow.)

    Consider that whether there is or isn't a patio, the water must leave the yard running toward the front of the lot. The patio surface will conform to grading that enables this scheme. The pitch will be subtle, seeming like a level floor, in spite of the fact that its surface is warped to create the slopes needed for drainage. Most of patio will pitch about 1/8" per foot.

  • sweetverve
    Original Author
    13 days ago

    Yaardvark, thank you. If I am understanding correctly, you are suggesting that the patio slope out and away from the house at 1% grade. At this grade, there will be a height difference between the edge of the patio and the surrounding lawn/garden beds (3 to 5" at 1% grade).
    Where the patio meets the lawn (where the height difference will be 3"), perhaps we can address this height difference by removing a bit of soil around the lawn edge, effectively creating a swale at the patio/lawn junction.
    At the deepest part of the patio (on the west side), the patio will adjoin a garden bed with a big elm tree, with a height difference of 5". Not sure how to address this.

  • sweetverve
    Original Author
    13 days ago

    I think I understand it now. Seems like we would have to slightly re-grade the garden beds as well. Where you indicated the drainage (the light blue dashed line) - would a french drain be necessary, spanning the width of the yard, or at least of the patio in the rear? We have never seen standing water in the yard during heavy rains so far.

  • PRO
    Yardvaark
    12 days ago

    I'm describing surface drainage to you. Yes, the non-patio areas would participate as much as necessary. No need for underground drainage.

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