What kind of edging should I use between a patio and a French drain?

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Old 10-25-14, 07:36 AM
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What kind of edging should I use between a patio and a French drain?

Here is a diagram of what I am trying to achieve
My patio is pretty much flat. Due to settling the water collects near the wall
Since it is too much work to grade properly the entire patio I think that it would be good to rest the areas where the water collects and to add a french drain between the patio and the wall. The wall is presenting efflorescence due to too much water at the base. The water goes up on the wall due to capillarity pressure.

So ..what sort of can be used between the french drain and the patio (see the picture, the edge pointed by the arrow)

 
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Old 10-25-14, 09:27 AM
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PF4DIY -

It seems like you are getting a little too to complicated regarding the rain fall out side and especially below ground.

1). Do you have gutters and downspouts or are you dealing with direct rainfall or rain and windblown water toward the home?

2). Your 2 concerns are the drainage of the patio. Since you have chose the slope, that cannot be changed. Interlocking pavers are not waterproof, so water will always penetrate the surface some what and be carried away by the uniform thickness sand settling bed if it can not penetrate the base. Similar installations have been done you decades on streets, patios, driveways and sidewalks in Europe for decades.

Draining that area into the "french"drain area is not really good because the surface collection area of the drain area is in direct contact with the house wall that has some efflorescence showing above grade. That is not good to collect water against the side of the house foundation. The wall should be waterproofed (you can go as far as a rubber barrier or something not as perfect), but that will require some excavation and resetting of pavers. The perforated pipe at the bottom of the french drain area will carry the water away.

3). The pavers can be run directly up to the house foundation at the slope you have decided on. If you want to go further into details, you can use a backer rod between the waterproofed foundation and caulk the joint.

Those are some suggestions without tearing out everything.

Dick
 
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Old 10-25-14, 10:35 AM
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Hi Dick

As always, very good advice, thanks

1) the house has gutters, the only purpose of the french drain is to carry away the water that might still come to the wall under the pavers.
My concern is that the soil bed was not graded properly or it settled and now it is lower near the house. Otherwise if the sand or the gravel layers deteriorated the soil bed if properly graded should have taken the water away and that is not happening since the wall has efflorescence

So I do not think that I want to dig down to the soil bed level. and to correct everything from that level up
My plan was to level the pavers and let the french drain take whatever water might get through and reach the wall at soil level.
In other words it got too complicated near the wall because I simplified the work on the patio itself.

2)I do intend to grade the pavers as much as I could or at least to reset them because right now there is lower spots next to the wall, so no I do not want to use the french drain to drain the patio, it is more of a protection. The patio will be graded in the opposite direction of the wall.
Yes I was planning to insulate the wall as much as I could for the depth of the french drain.
I would also like to put plastic foil at the bottom of the french drain

3) I am not sure if I got this right. Are you suggesting to run the pavers all the way to the wall above the french drain? If yes, how do I provide a stable bed for the pavers? Do I put sand on top of the french drain gravel? That will not be compacted ..will it be stable?

 
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Old 10-25-14, 12:24 PM
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Just put the 2" sand on the french drain system (compact the surface a bit if possible). The sand is for a setting bed and you actually have a little more sand than the recommended 1" thickness, so the excess may cause a little more settlement initially after you vibrate the pavers in place. When you think about it, your granular french drain backfill is contained on the sides and under it.

The grading of the compacted base and the excess sand are not major problems for a patio. The compacted base is ideally used to control the drainage pattern and the uniform 1" sand setting bed is just the to provide a thin 1" uncompacted layer of sand to vibrate the sand into the joints and create a uniform smooth base.

The plastic foil is not necessary.

The way to combat the disliked efflorescence is to prevent the brick from being saturated IF they are the type of brick that have severe absorption.

Dick
 
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Old 10-25-14, 04:35 PM
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Thanks again Dick!

I just bought this Laser level set | RONA and measured the slope for the patio.
North South (on the picture) the patio is graded and it is OK, the slope decreases gradually toward North
East-West, especially in that area where the water collects, it is level or lower close to the house,

The patio seem to had been designed to drain the water on the north west corner, however there is nothing like a drain or like a channel there. I will have to find a way to drain the patio, especially since this seem to have been installed using polymeric sand which from what I read is less permeable to water...

 
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Old 10-26-14, 05:39 PM
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Hi Dick

I crunched the numbers and it looks like I will have to use 4" perforated pipe
How deep should I dig to install this pipe considering the circumstances?
 
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Old 10-26-14, 06:55 PM
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As deep as you can to drain without a pump. Keep the holes in the pipe on the bottom half of the pvc pipe. Dig deep enough to have a couple of inches of well drained soil under the pipe.

How in the world do "CRUNCH" numbers on something so vague?

Dick
 
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Old 10-26-14, 07:46 PM
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How in the world do "CRUNCH" numbers on something so vague?
There seems to be some science behind it. See page 29 and following of this doc
http://www.ndspro.com/images/stories...r-drainage.pdf
 
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