I have a small backyard that ends off with a steep slope which leads to some sort of sewer / creek at the bottom. I have already gotten a wooden wall built behind my porch, which is now separating from the foundation of the house. Apparently that wooden wall wasn't enough and now the dirt next to the wall is starting to wash away into the ditch. I'm thinking about putting up a retaining rock wall but then, I am also concerned if the retaining rock wall will be washed down into the ditch after a couple of rain showers. What should I do about this problem before my entire house washes away?

amricca

Best thing would be to plant some grass that will keep the soil in place. Boulders are also a good way to retain without having to build footings for a wall.

loricar

terracing, either with wood spikes set deep, or better, rock retaining walls. Quickie method would be landscape fabric to stop the water erosion. Combination of methods for short and longterm solutions, and if all else fails get a landscape architect quick!
good luck
loricar

smearcase

Not knowing exactly what the situation is. the only suggestion I have is to stabalize the slope with an excelsior matting type material, which consists of fiberglass netting which sandwichs a wood fiber or other biodegradeable material. Grass seed is planted before the matting is applied, and when the grass comes up it grows thru the matting and becomes very sturdy. This works well on steep highway slopes.
It is very important to have the backyard drain well. I dont think you want to try to protect the slope by slowing the flow of water away from the house. If you do retaining wall type structures you need drains to take the water away from the house side of the wall.

smokedetector

You mean the wall is in place still and the dirt is slipping through the cracks or something? If this is the case, put a piece of landscaping plastic/fabric between the dirt and wall.

If the wall is not holding, you can try repairing it by putting pieces of rebar in the ground as staves. Go at least as deep as the height of your wall, and space them at least every few feet.

Dennis151

have you tried using a different type of dirt ? if you build a bulk head you dont want it to retain water

ArchSteve

Hello ajt0...
Without some specific details, it is a bit hard to answer specifically, but it definitely sounds like you have some things working against you that are inherrent in the soil type.
First of all, it sounds like the "wood wall" you built at the back of your patio is not stable enough to retain the dirt and the dirt has a lot of either clay or organics in it - those types of soil tend to hold water and move as a mass.

I will suggest a number of steps, each of which will work together to address your problems:
1) create a series of terraces with heavy timbers or self-stacking concrete retaining wall systems. Depending upon the size of the drop from one terrace to the next, you may need to reinforce the walls by driving a piece of rebar through the wood or down the center cores of the retaining blocks. The walls will need to extend at least 12" below the dirt on the low side and be set on a stable, gravel base.
2) At the base of each terraceed wall, install about 6" of small gravel below the bottom of the wall. Make sure this layer is level and well compacted.
3) After laying the bottom course of block or landscape timbers, backfill with gravel until ou are about 8" - 12" higher than the final grade on the low side.. At this point, lay some PVC perforated pipe along the back of the wall and create a way for drainage water to get out of the pipe and through the wall to the low side of the wall - about every 6' to 8' should be fine.
4) Go ahead and back-fill the dirt behand the wall. Add some sand and smaller gravel to the backfill - this will help the soil to drain and will break it up a bit. Don't build up more than 4" - 6" before compacting the backfill and making sure there is gravel immediately behind the wall.
5) Plant whatever type of plantings you want on the terraces - as long as they do not have large-invasive root systems. The Sales Assistants wherever you buy the plants should be able to help you make selections that are appropriate. I would suggest low-maintenance series of plants that are native to your area - and don't go too large either (no trees).
6) As you build up the terraced wall, backfill behind the wall with gravel at least 6" behind the back face of the wall - again well-compacted. Grass may be fine, but most grasses have shallow root systems. Deeper root systems will work better to stabilize the soil.
7) As the terraces work their way down the slope, work on diverting the water towards the drain at the bottom. (Someone obviously anticipated there would be substantial water needing to be drained away - use it to capture your excess water needing to be accomodated.

Hope these suggestions help.
If you have any additional questions, don't hesitate to contact me.

ArchSteve.

motionspace

Earth movement is a serious issue and if you are concerned about your house moving, definitely consult with a geotechnical engineer. A geotech will be able to give you solid recommendations that will hopefully keep the house in place.

Motionspace Architecture + Design

motionspace

You can find a geotech either in the phone book, or on the internet, or call a local architect or structural engineer and see who they recommend.

Motionspace
Seattle Architects