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Drainage in garden bed and seepage in basement

Posted by natureboy8888 Portland, Oregon (My Page) on
Sun, Jul 6, 08 at 7:32

I have seepage problems in the basement in the front of my house, and would really appreciate some guidance to correct or minimize this when I am converting my front yard to a garden.

Details: I am going to convert my front lawn to a potager garden, a more symmetrical and formal garden of vegetables and ornamentals. This will involve putting in several beds (level with the path) and paths (either gravel or pavers) all running parallel to the face of my house. My front lawn slopes about 3.5% from house to sidewalk over 20 feet(a rise of about 15 inches). Currently, the lawn near the house does not slope until about 6 feet out, which can't help the current situation. The seepage is fairly minimal and interior wall patching has stopped any seepage for the past 4 years. During our wet winters though, the wall is a bit moist and trickled in one spot before patching.

Plan: I would like to have a constant slope for the entire width of the garden. Nearest the house, I'll have a 2 foot wide bed, then a 2 foot wide path, than a 4 foot wide bed, and so on to the sidewalk.

So, what do you all think? I'm concerned the alternating beds and paths may trap water near the home. I'm also a little concerned about having beds sloped, although I doubt such a mild slope would cause any real problems.

Follow-Up Postings:

RE: Drainage in garden bed and seepage in basement

My mom, a retired real estate broker, used to have a rule of thumb. She didn't like representing houses with yards that sloped toward the home. I'm not saying she wouldn't, but she reviewed them much more carefully. She lives in a city that is hilly and has many subdivisions prone to flash flooding. She simply preferred to sell houses without drainage problems.

Now, the weird part is that she and Dad bought a home with a serious grading issue. It was a new home at the time and nothing had yet been done to the landscape. They had decided to walk away from this house because of the potential drainage problem, but kept coming back.

The homeowner (developer) paid for a consultation with a LA and reduced the house price by the amount needed to address the problem. I don't know the percentage grade, but the ultimate fix involved a dry stone retaining wall that blends into the ground, creating upper and lower regions of level ground. The wall at its highest is about 2.5 to 3 feet? I know that the walkway from front door to upper level goes up six steps.

The point is that the first 20 feet or so of front yard is sloped away from the house. It's subtle, but essential. There is a french drain (sort of an installed underground stream bed) at the base of the retaining wall which provides water with access to the street. It's a corner lot, if anyone is following this.

My point, which has probably been hopelessly lost in this long story, is that slope matters.


RE: Drainage in garden bed and seepage in basement

Thanks for the reply.

I guess my concerns arereally:

1. Will the path (which will be more compressed than the beds) will interrupt the flow of water away from the house?

2. Will I have problems is the 4 foot bed is 3 inches lower on one side?


RE: Drainage in garden bed and seepage in basement

If I am understanding your post correctly, the lot slopes down from the house to the sidewalk but not until out about 6' from the structure? If so, before constructing your new potager implement a drainage course next to the house - a trench 12-18" deep with a perforated drain pipe connecting to the storm water system, etc. or otherwise directing the collected water away from the structure and filled with crushed rock. Make sure any downspouts in the vicinity feed into this french drain as well. As this will most likely be behind any raised bed and pretty much not visible, I'd just leave the crushed rock as surfacing unless you want to fancy it up with more decorative river rock. A drainage course adjacent to the foundation like this is relatively common for residences in this area, especially with single story homes with a broader eave or roof overhang.

To answer your questions:

1) If the path is permeable and constructed with a proper gravel/crushed rock base, no.

2) No :-) Although visually, it may look better to have the bed level, so that the material it's built of will have a slightly different depth from back to front. However 3" is not much of a grade difference, all things considered.

RE: Drainage in garden bed and seepage in basement

  • Posted by bahia SF Bay Area (My Page) on
    Mon, Jul 7, 08 at 1:17

Not clear if the yard slopes down to the street from the house, or towards the house from the street. Also, do you have gutters on the roof eaves and do they connect to a downspout that is directed away from the house, or is part of your moisture problem really excess accumulation of rainfall from the roof? If you are dealing with no gutters/downspouts or they don't take the flow away from the house foundation, and/or the slope is towards the house from the street, you need to address your drainage issues in a more intensive way that what you have proposed. It is unclear from your reply to the questions as to which way your front yard slopes relative to the house. If in fact you do have gutters, downspouts and slope to the street, all that may be required is to extend the downspouts further away from the house, and make sure you don't have drainage from the sides and/or rear of the house that is also a source of water infiltration into the foundation at the front.

RE: Drainage in garden bed and seepage in basement

It sounds like you'll be improving the slope, starting at the house. Definitely a 'must do'.

The only problems that I can see with pathways would be -- make sure the edging doesn't trap the water, causing it to pond on the house-side of the path or planting bed. This is caused, sometimes, by improper installation of edging -- not installing it flush.

Also, try to make sure that your pathways are also sloped just a bit -- which I think you said you'd be doing anyway.

Best of luck!

RE: Drainage in garden bed and seepage in basement

French drains.
Downspouts routed away from the house.
Rain gardens.
Dry streambeds.

Our large meadow slopes down to the house. We created a perennial garden to hold the slope in place, a rain garden at the bottom to allow water to slowly seep into the soil and a dry streambed to route it all away and save our driveway from being washed away. Our downspouts and our water feature overflow also dump into the dry streambed.

Because this all eventually dumps into a natural creek on our property, we use only organic products to protect the environment.

We just had a series of gully washers and I blogged about what we did. We also have a fenced cottage garden right in front of our house. There is a manmade stream so the the water that temporarily collects on those paths either seeps into the garden or runs off into the stream.

I don't know if your situation is similar, but I have a lot of photos on my blog. Our crawlspace is totally dry. My husband checks it regularly (everytime he changes our wholehouse water filters).

Cameron (in North Carolina)

The rain garden right after a big rain (it is drained within an hour or so):

Here is a link that might be useful: managing heavy rains in the garden

RE: Drainage in garden bed and seepage in basement

Your potager garden will certainly be the focal point of your property. You and the above comments do no really address your biggest problem, damp basement walls. Gardengal48 got closest to a solution. Twelve to 18 inch trenching is to shallow. You need to go down at least 3 feet to get the best results. Water moves vertically in soil before it move horizontally unless you have heavy clay.

RE: Drainage in garden bed and seepage in basement

It is probably too late to impact this particular post, and I hope the initial plan worked out. I thought I might post my experience with water in the basement. Our last house, in Seattle, WA, was built circa 1940 on a slope down toward the back of the house with a daylight basement, with the basement at street level in front. The upper (second floor) level is even with the back yard. The previous owner had partially finished the basement and installed a curtain drain and sump pump to drain water under the slab (basement floor). But there was still some seepage through the basement wall on the uphill side. Part of the problem was a patio in the back that sloped (very mildly) toward the house. That, coupled with an old nonfunctional footing drain (at the base of the foundation) meant that all the water from the backyard drained across the patio, down along the foundation, and had nowhere to go. That pressure helped force the water through even the smallest crack in the foundation (basement wall). My point is that, regardless of what happens to the slope and surface water, you will likely have water seeping into your basement unless you dig down to the footing, reseal the concrete, install new drain and drain rock, and make sure the water has someplace to go besides into your basement. Ours was a huge project but worked very well.

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