Ask a Question forum: Lawn drainage

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Sep 18, 2016 11:15 AM CST
A client of mine has recently had a new bluestone patio installed. As you can see from the photo, (during construction) the paving is laid to allow rainwater to flow to the edge of the grass/paving. I laid the new lawn with the sod at the same grade as the paving, as you are supposed to do. That allows the mower to run along with one wheel on the paving and cut the grass without the need for a weed wacker.
My client is complaining that after a rain the water is trapped at the auction of the paving and the lawn.
He is asking me to take up the sod and lower the soil so that when the sod is relaid it will be lower and allow the rainwater to run off.
I am planning to suggest installing a French drain at the junction of the paving and lawn and pick the water up and run it away beyond the hedge, that you can see in the top right of the pic.
I will look forward to hearing from you.

Thumb of 2016-09-18/johncowen/32c755

Name: Daisy
Reno, Nv (Zone 6b)
Not all who wander are lost
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Sep 18, 2016 2:52 PM CST
Hi John, Welcome! to NGA

It seems to me that if you lay the sod at the same height as the pavement, you will end up with water lying in that junction and even backing onto the patio. What's working against you is the height of the grass itself. And as the turf builds up, the problem will be worse.

A French drain seems like a reasonable solution to me. It would be better yet if the home owner would let you install a gravel top or French drain cover over the drain. It would only need to be a couple inches wide. I think if you put grass back over the drain, it will work only until the grass gets thick.

Name: Greene
Savannah, GA (Sunset 28) (Zone 8b)
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Sep 18, 2016 3:20 PM CST
Looking at this only from the viewpoint of the customer and assuming the work you did was exactly as described on the contract.

If you want to do a bit of extra work just to make the customer happy, then yes, lower the sod a bit, but get the agreement it in writing or this could go on forever. A satisfied customer is your best form of advertising.

On the other hand, if you give the customer an estimate for the cost to remove sod, dig a trench, install a French drain, replace the sod (or go with the gravel/stone option), which would involve an entirely new contract, I don't think the customer would be pleasantly surprised. And since you would be doing the job while walking/digging/hauling on the lovely new delicate sod you'd need to take precautions not to "damage" the sod.

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Name: Rita
North Shore, Long Island, NY
Zone 6B
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Sep 18, 2016 4:31 PM CST
If I was the customer I would be unhappy and want the sod lower like I felt it was supposed to be. Anything else is simply making things complicated in my opinion. Sending off water that could be used to water the lawn.

Name: Rick R.
near Minneapolis, MN zone 4a
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Sep 18, 2016 6:56 PM CST
Welcome to the forums, John!

It looks from the photo, that the sod adjacent to the bluestone is already lower? If the bluestone is sloped toward the grass, and the grass also continues the slope away from the bluestone as you claim, I don't know why there would be water pooling at all. Confused Did the sod near the bluestone sink to create a slope back toward the bluestone, thus catching the water?

The general grade needed for hard surface water runoff is less than what is needed for any soft surface (i.e., a lawn in this case). This is because it is impossible to grade any earth surface at such a shallow grade, so that after settling, every square foot drains as desired. I'm sorry you read somewhere that an equal minimum grade for hard and soft surface water runoff is acceptable, but I would consider throwing out that book. Landscapers will put in a sharper grade, at least for a short distance, when they know excess water will exit to that area. Ummm..... doesn't that make sense?

Sorry to be so harsh. I know this isn't a namby-pamby answer, and I'm just not good at beating around the bush. Unless I am not understanding the problem correctly (which could be very true), it seems that it is the design or the installation of the sod (or both) that is at fault. If you can fix that, there will be no need for a French drain. Natural drainage is always better, longer lasting, more environmentally friendly and easier to change in the future, than any French drain.

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