Paver Patio - French Drains?

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  #1  
Old 09-06-19, 02:34 PM
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Paver Patio - French Drains?

Hi there,
I have a fairly small backyard in which I am installing a paver patio. The soil is heavy Norcal red clay, so there is a major drainage issue - after all the heavy rain this past winter the whole patio area was a pond for over a month after the rains stopped, and it took over a month for the deeper puddles to dry out; so many frogs moved in it has become known as the "Frog Apocalypse."
My initial plan to handle the drainage was to give a thicker base of rock (10"-12"), and run french drains with a couple of catch basins between the patio and the fence, leading down the side of the house into the front yard (see fig. a).
My concerns about this are 1) the large tree in the corner of my neighbor's backyard is very likely to cause a lot of headaches with the drains running essentially through it's root system
and 2) I am concerned that french drains that close to the fence posts concrete anchors will destabilize the fence.
Would it be a viable option to run the drain UNDER the patio if I included catch basins outside the patio area and a drain in the center (fig b)? If so, what would be the best way to do this/what materials would you suggest.
Thank you for any help you can give me!
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  #2  
Old 09-07-19, 03:43 AM
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1. Yes, digging through roots can be difficult especially if digging by hand. Find out what kind of trees they are and see how tolerant they are of having their roots disturbed. Here in the east I really try to avoid disturbing some oak tree roots as it's relatively easy to kill even a large tree.

2. Yes, excavating near the fence posts can cause problems.

I have a couple 4" sch 40 PVC drain pipes under a portion of my paver patio. I paid careful attention to have a deep, properly compacted base and get the piping as far below the patio as possible. It was installed in 2011 and still looks great with no cracking or movement of the pavers.

I would consider the surface as the primary source of water as opposed to catching water moving through your gravel base. The paver patio will be mostly impervious to water so most water hitting it will run off instead of soaking through. Maybe include some pits/chambers with drainage grates to catch water coming under the fence and off the patio.
 
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Old 09-07-19, 01:41 PM
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Thanks for your input.
Are the pipes run underneath, or imbedded in the rock base?
 
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Old 09-07-19, 03:37 PM
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My drainage pipes are in the rock base. I took extra care to make sure the stone was completely under the pipes with no voids and was well compacted. I have about 4" of stone on top of the shallowest pipe.
 
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Old 09-07-19, 06:40 PM
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In a similar situation, I subgraded where I wanted it, dug the trench, laid the pipe, brought it up to the subgrade with pea stone, and laid my stone right on that.
 
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Old 09-14-19, 06:13 PM
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Check out french drain man on YouTube. Lots of great videos.

If you're going to run the French drain under the patio perhaps a channel drain would work too? It really depends on how you set it up.

Just remember open faced drains like catch basins have a tendency to let in more contaminants than they catch if you have a lot of surface water flowing into them.
 
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