(Almost) Free Raised Beds

gwtamaraJanuary 1, 2013

Often new gardeners desire to have raised beds and wonder what would be the best, cheapest, or longest lasting material.

They are also sometimes faced with ugly concrete slabs that they want to remove. The following is a way to deal with both issues and all you need is the desire and a strong back. If you spaced it out over a few weekends it is well within the capabilities of most folks.

The main things you need are the aforementioned strong backs, some simple tools and the vision to see the finished product.

If you find that your slab has embedded wire mesh or rebar in it all bets are off. The hassle of cutting thru the mesh/rebar and the inevitable raw metal sticking out of the edges will make this project MUCH more difficult and the chunks will be for the most part unusable.

You wouldn't want a wall full of rusty, raw metal edges anywhere near your garden. If you find this is the case call someone in to remove the concrete slab for you and start with a blank slate.

The term for this is Rip-Rap. I had a link with a detailed how-to on doing this but I can't find it so I'll try and explain the process myself.

Some other advantages to this are, you are getting free material that will last a very long time, you are recycling, and you don't have to pay a large disposal fee to remove the slab. You will need to remove some debris, but with planning it will be much less than the cost of hauling away the entire amount. The first thing I'd do is sketch out the future locations of the beds before the demolition. This will allow for you to plan the beds to use up as much of the slab pieces as possible, minimizing the amount of debris you need to remove. A very rough estimate would be 1 running foot of 12" high wall for every 4 Sq. Ft. of slab you are removing. This will depend on how thick the slab pieces are and how wide a wall you are building.

Use a pinch bar and a heavy sledge to smash the slab into pieces. You can try for uniformity of size with the pieces but this is very much hit and miss in practice. Start at a convenient corner and pry up the slab a bit with the pinch bar. This allows the cement to break fairly easily with just one or two hits from the sledge. Just work thru the slab using the busted pieces as fulcrums for the pinch bar. If you try to smash up concrete without lifting it up a bit you will find it VERY hard going. The sub-base absorbs most of the force of the blows and you will quickly wear yourself out. You could rent a jackhammer but in practice the "Lift and Smack" method works much faster on most average slabs you will find. Once you have the cement reduced to manageable sized pieces clear it from the areas you wish to the have beds in. Clean the debris down to the soil. Prepare a level trench as wide as needed and a few inches deep to define the edges of your walls. Place a layer of leveling base in this trench (stone dust, coarse sand, or if you are so...

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