raised bed/sunken patio

[SimonMilton]

I'm thinking of building a sunken patio and using the soil for a raised bed. I have quite a lot of timber from felled leylandi and was thinking of using sections of log (about 15cm diameter) vertically in a row for the walls of the sunken and raised areas. My question is how far below ground would these need to be burried to stop the walls collapsing. If the sunken area is a foot deep, would another foot below ground be enough? The answer decides whether I have enough wood or not. I don't want to concrete them in.
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[Thermo]

if i get the idea of what youre doing then yes should be ok

 

[noseall]

drainage for the sunken patio may be an issue?

also, a foot deep swathe of virgin soil will go a lot further than you think.

in other words, don't expect to get rid of it all on a similar sized project above ground as disturbed soil is full of air, and will fill a greater volume like for like.

hope this makes sense.

 

[breezer]

you mean to say "dig a whole and then put the dirt back in it, you will find some left over"

I would also see if you cant put a batten on the back to join them together

 

[SimonMilton]

thanks for your replies.
Yes, i did wonder about drainage. It might put me off the idea. Maybe gravel at the centre of the patio and outside of the log wall would do?
Good point about the soil. But a little extra topsoil spread around shouldn't hurt.

 

[noseall]

you will need more than a bit of gravel to cope with a good deluge, or you could end up with a muddy dirty patio area.

 

[hhoang]

Well, I did exactly what you're thinking about last year. I dug out a sunken patio, built a planter bed on the side to put some of the dirt in it. The results were very satisfactory for the sunken patio. However, we experimented by digging about 20" below the surface of 8' x 9' sunken patio in order to put a 10" layer of drain rock, then about 5 inches of sand underneath the concrete pavers.

Last month, we had 2 weeks of intense rain and the drain rock was insufficient in capturing the water. We have basically clay soil in our yard and as a result, the sunken patio filled with water. Granted, it drained once the rain stopped over the course of the next 24 hours, I was embarrassed to have a little pool on my hands. So, I suggest implementing some draining system. Because we don't have a slope, I didn't have a natural solution. Now that we know the results, we'll have to get some drainage for next rainy season.

For fun, here are photos of the sunken patio and succulent planter bed.

http://flickr.com/photos/39406128@N00/sets/72157602614808392/