Front yard advice
I live in sunny Vancouver, Canada...where it rains...alot! I have recently built a retaining wall in my front yard and backfilled it with hardpack (lots of clay with a little dirt). I did put down several yards of 3/4 crushed gravel under the hardpack and lining the wall.
I now need advice on what to do next. I would like it level as I am going to put grass down in the spring.
What is the best next layer - sand, topsoil? Keep in mind the new dirt area you see contains alot of clay and I don't want to run into drainage issues.
Thanks for any help or advice!
Keep in mind that sand + clay = brick. Commonly called adobe in the SW.
Here's what you should do.
Get some of your current soil. Put in in a quart glass jar to about 1/2 full. Fill the rest with water. Shake it up and let is settle for an hour or so.
Once it has settled it should have 3 equal layers.
The bottom layer is heavy sediment, the middle layer is cloudy water (the clay) and the top is organic material. If the layers are not equal then you will need to beef up that layer.
Here is how yours will look. Heavy with sediment and water and very little organic material on top. Let me know how close I came.
If that is the case then you need some organic material. I suggest about 6 inches of organic and mix it in with 6 inches of your existing clay. This will give you the mixture you need. To get a nice lawn that needs minimal watering you should shoot for at least 6 inches of a good mixture of soil. The problem with clay is that it doesn't allow for draining and soon the roots will reach the clay where there might be sitting water and will cause the roots to rot. I prefer 12 inches of good soil which will make for a nice green lawn. Most of the time that requires removal of some of the old soil.
Also when you get down to the level you want cut some small trenches in to help drain water away. Put some small rock in there to keep the void from filling with more clay.
I am not sure where the sand bit comes in as I hear that a lot. But here in the northwest that will just make hard compacted soil as it settles. You need organic material for clay soil to keep it from compacting.
Most people live near rivers or lakes since almost all cities were founded around water which is important for life. Since these cities were on rivers or lakes the surrounding soils were composed of flood debris from past floods. Clay is part of the process when water scourers rocks and creates that very fine powder that acts like a glue. So almost every area of the country has clay as part of the soil at least where most people live.
Hey, thanks for the detailed post, alot of great advice for a newbie like me.
What kind of organic material would you suggest and where could I get it? Also, I am planning on putting about 12 inches of topsoil as my last layer before laying the grass down, if this is the case do I still need to mix the organic material into the clay? Lastly, would I still be wise to dig out channels and fill them with small rocks for drainage or would the foot of topsoil allow for sufficient drainage?
What you should have is a mix of organic and your clay. Clay is not bad in moderation. The problem that most people have is that clay is all they have and that is the issue. I doesn't drain well and it is hard for roots to go deep.
That being said all organic will not allow for structure and the ground will be spongy like the old growth forest floors.
Clay and organic should be a 50/50 mix. Organic on top is fine but should not be as deep as you intend. At least I would not do that. I would look at 1-2 inches.
Organic material is generally compost found at the local recycling yard which most sizable cities have. It is a growing business with all this recycling.
The only reason that I suggest some drainage is because I have seen lawns that have a clay bowl and the water just sits there and doesn't drain at all. It becomes stagnant and can cause all kinds of problems with lawns. The most common is a yellow lawn which is from too much water. Roots from lawns can grow to 12 inches.
You can't go wrong with drainage. If you have access to the bare ground then slope the hard clay in one direction which will make sure there are no clay bowls to hold water. If the water is drained away you have nothing to worry about. Don't slope it towards the house. That is bad.
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