I have been using raised beds for several years now. I converted an existing patch of grass into four, 4ft x 12ft raised beds for a total garden area of 192 sq. ft. This could, conceivably, produce enough food throughout the year to make a serious dent in the food budget. And, of course, all the advantages of raised-bed gardening are realized. However, I have had to replace several end boards due to rotting out at the corners. In order to prevent this from happening, I came up with a way to use concrete as a corner brace, and thereby stop the rotting and make a more permanent installation. Starting in step 7, I show how to replace an end board that has rotted out at the corners.
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Signing UpStep 1: Materials Needed
The usual concrete tools, materials and supplies. For my mix, I used a ready mix concrete so that I would be sure to have a uniform, strong concrete. For the bed itself, I choose to use 2x dimensional lumber. At least one bed is made with 2x12's, one with 2x10s, and so on. A 2x6 is certainly big enough, so it is a matter of personal preference. In this instructable, the lumber is 2x8's.
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I love your design. I am pretty sure Hubby will dig it. Since he is the "builder" he needs to like it. thanks,
Is 4X12 a functional size?
Do you put any chicken wire across the bottom to limit gophers?
Can you add an upward post to the corners for a fencing around the garden? (to keep the dogs and cats out of the garden.)
Thank you so much. Sara
OLD CCA lumber has been banned for consumer use since 2003/2004 ... Arsenic was the main component there that was causing problems... Pressure treated wood now still has copper in it... but copper interacts with other metals in the ground not really plants... Some people even plant copper wiring to ward out snails and slugs as pests in their gardens!
I've used pressure treated wood in my raised vegetable boxes and its been great!
Really, I think some people take this organic thing a bit far....
Remember, most of your plumbing (other than the waste/discharge lines) are made of pure metallic copper and has been for generations and hasn't caused problems...yet...
Side note: cement production *is* one of the largest contributors to the rise of atmospheric CO2 but when used carefully in small amounts and for durable uses like in this project, it can make up for it.
I built one next to the house for plants. It was a two-tier with a shelf above for plants that hang down over the pots. Really looks great! I handled the rot problem (I hope) by pouring a concrete footer under the boards to keep them off the soil. I like to 'mound' the concrete to cause any water to run off. I just use a form of level 2x4's staked in place where the planter was designed to be. Then I dug holes 18" deep for 2x4 posts in the corners and every 4 feet. These I cut from a single 4x4 treated with .060 ppcf ACQ for buried conditions.These posts are concreted into place as this bed is to be permanant. Then I paint on a sealer (stain in this case) to preserve the wood from the effects of weathering--pressure treating stops the rot, sealers stop the weathering... two different things. Two thicknesses of heavy plastic sheet is used for covering the inside of the 2x8 boards that retain the dirt. The sheet is folded over about an inch wide three times, then stapled on top, and the staples are covered with 3M 5200 sealant to stop any water penetration. Then it's draped down the board, and into the planter about a foot.
Now I screw down a sealed but not treated 2x4 on the top to resist bending pressure against the 2X8's, make the top attractive, cover the plastic, protecting it and shading it from ultraviolet radiation. I cut the 2x4's drill them for the galvanized screws, put in the screws and add more 3M 5200 sealant top and bottom to keep water from entering, then screw down the boards. Sometimes I come up from below ground with a PVC twin pipe watering system that can be put on an inexpensive timer, but I didn't in this case as it contains basically shrubs and flowering plants I won't eat. Then I fill it with clean soil, mounding it about 4-6 inches in the center, and bringing it to within one inch of the bottom of the 2X4 topper. Next I cover it with the sturdiest black plastic sheet I can find, tucking in the edges all around about 6". This contains the mound I made in the center, heats the soil for better growth, and inhibits weed growth. Finally I cover it with mulch or even another inch or so if soil. This brings it to the lower edge of the 2x4 topper, covering and hiding all the plastic.
I wrote this quickly and in brief, so pardon me if I missed anything, but that should keep the 2x8's in good shape up to a theoretical 20 years. If you want a belt and suspenders approach, additionally paint the wood with a propylene glycol (antifreeze) borate solution to extend the rot protection. (formula online here) The 2x4 topper will rot, but it's easily replaced and inexpensive. To plant, I cut a small 'X' in the plastic and put in my plants.
Here in East Texas, where the soil can be used without additives to manufacture very high quality bricks (red or yellow clay), this raised bed gardening is extremely popular. Hmm, perhaps, necessary is a bit more appropriate term. I was building an area in the back to have a concrete floor, and made a flattened area, dished to later get a central drain, but nothing else had been done. It rained and the water, five inches deep and ten feet across, remained for more than two months. Makes for an easy swimming pool, eh?
I am a former sailor and very familiar with the problems of wood rot, so I prefer the more involved process. I'm use to it, love the detailed, scientific approach, and I seriously doubt I could actually put down wood and expect rot when it is reasonably easy and inexpensive to get all my web-footed swimming birds of the family Anatidae in a row and maybe, just maybe, not have to ever do it a second time. Plus it looks bloody great stained, mate!
I sincerely enjoyed your instructable, and I thought your concrete corner post idea was noteworthy. I am going to run it through the processes a bit more, but it's an interesting idea. Might use it myself. Can't rot that stuff, huh?
Thanks all around for the effort you put in and the quality of your work. Much appreciated!
Oh, one more thing. Those who feel that the treated wood would be dangerous around gardens, or the leaching of concrete too alkaline, might consider the amount of chemical likely to permeate the soil to any significant PPM over distance. I have not checked specifically, but given some nominal considerations, I find it unlikely that any effective molecular transport mechanism exists in garden soil. If the contaminates make it an inch or two from the site, in any appreciable/damaging PPM I would be surprised. Are there recorded instances of death or illness (esp with ACQ) directly attributable to raised bed gardens or similar constructions? Additionally, the 2X8's are only ACQ (20 ppcf) as they are not intended for ground contact. I have done this before and eaten the fruit, roots, etc. I'm almost 70 and I still feel like I could successfully take on a full grown supremely conditioned male baeolophus-- even during mating season when he is fully charged with strength building hormones. . . and prevail.
http://k43.pbase.com/g6/15/373415/2/69828942.DiiTyh8t.jpg
Back on topic, this is a very useful instructable; thanks! I'm pretty handy constructing forms out of cement, and it never occurred to me to do something like this. I very much want to start a raised bed garden with drip irrigation. The house I'm in right now has almost no yard in full sun; the next house I purchase will definitely have room and proper sunlight for raised beds.
I've seen raised beds where they attached tar roofing shingles to the inside of the 2x10's to help keep them dry. Any opinions on that tactic?
My garden is completed except for a revision on the topping boards which suffered from inconsistent corner height as the boards moved from sitting on them and the corners twisted uncontrollably. I am replacing the topping 2x4's and adding either a wide half-lap at the corners or routing a space under the corner joint for a 1" support that holds the corners together more securely. That should allow sitting and standing without the twisting problems.
The garden has been growing for a year now. I love the raised bed appearance, and especially the old bricks with the stained 2x8's making the walls of the garden. The 2x4's I put on top to make the edge wider have proved to be absolutely worth the extra effort and cost--except for the correctable problems mentioned above. The plants we have grown are the topping glory and because of a scientific approach, are mind boggling in size and scope.
Because of the soil I "manufactured: by collecting my food garbage and biodegradable wastes for "fermenting" in an old bathtub on my side yard I have excellent mulch, which I mixed with some imported black soil. (We have red and yellow clay as the predominant soil in east Texas) I also have drip watering on a timer and I administer correct does of 10-10-20 or similar plant foods, and additional chemicals plants benefit from. Epsom salts as an example. Epsom salts is actually magnesium sulfate, and activates many enzymes used in photosynthesis, plant respiration, and protein synthesis. It contains chlorophyll, which is responsible for photosynthesis.
Most home gardeners don't use a scientific approach and do not realize the usefulness of researching topics and augmenting soils, so they are struck dumb when they see my garden.
My home is in the middle of a pine forest thick with 50 70 foot loblolly pines. Only my tiny quarter acre plot was cleared and it still had five large trees. The garden is on the North- East side of the house and gets very little direct sun--less than three hours. Regardless, the elephant ears (Colocasia esculenta) my wife planted and tended did amazingly well. The usual size for this plant in the states is about 2-3 feet tall with a leaf about a foot across. What we got was true typical of tropical growth for this species with leaves to three and a half feet in length and more than two feet wide on a plant over nine feet in height.
The garden is raised almost 18 inches and the elephant ears (a dozen plants in a space eight feet long) dominate by growing in tropical profusion. Below them are plants of all sorts including shrubs, flowers, grasses, ground cover, creeping types, and so on of varying colors. There is a path in front of the garden and you have to work your way through them, pushing aside umbrella sized leaves coming from stalks the size of a mans arm.
We really love that area, and as our age allows, we will continue this plating and gardening approach until the back lawn is surrounded with a jungle of annual, deciduous and evergreen plants designed to provide a spectacular look year round.
If any of you are thinking of doing a raised bed garden, I sincerely recommend it and also careful use of good soil and plant foods. The results will please you more than you might expect.
We planted eggplants, pole beans, and cucumbers, all of which did fantastically. The cucumbers produced so much it was almost humorous. with 4 plants, we were harvesting more than 2 a day, on average during the peak. We also planted yellow squash and butter nut squash, neither of which did very well, and a few pepper plants that hardly produced anything at all. I got -one- jalapeno pepper the size of my pinky, and a single bell pepper the size of a golf ball.
What the photo doesn't show, and what was a surprising success was the EarthTainers: http://www.earthtainer.org/ I built 5 of them, and planted two tomato plants in each, and after I moved them around the back yard in search of sunlight (with the help of a dolly - those things are HEAVY when fully laden), the plants grew like weeds, and I was harvesting tomatoes until December 4th, when the first hard freeze killed them off. I highly recommend checking out the free plans he's got on his site. It only took a couple weekends (and a few trips to the hardware store) to get them built.
I used the soil mix in the earthtainer guide (potting mix / pearlite / bark fines) to fill the raised beds, and was very happy with it.
Right now, the beds are empty, although I'm about to toss the spent soil from the earthtainers into the beds, along with some leaves, and I'll throw some annual rye grass seed on top to act as a green manure.
I'm just getting started with this gardening stuff, so I haven't started composting yet (but plan to this season), nor have I set up drip irrigation (which I definitely plan to do this year). Scientific approaches always appeal to me, and I'll have to start tweaking added chemicals and plant foods too. I just haven't figured out the best vegetables/fruits to plant yet; definitely cucumbers/eggplants/pole beans, but I'll have to try some different ones this year, too.
Thanks for the update, I'm sure I'll have more questions in a few months!
On the shingles. Sorry, they won't help unless they are sealed both top and bottom and side to side. Water can and will enter anywhere they are open to the environment--through the cracks between where they join. I'm using two layers of 4 mil plastic to accomplish the same thing and sealing the overlaps with 3M's 5200 (read the specs first-here) Regardless, the plastic is in contact with the wood and will create an area where there is no air circulation to remove moisture. This creates the moist, warm, dark environment the many fungi responsible for wood rot can flourish in. Anytime the moisture climbs above 20% (and includes the conditions I described above), these fungi will generally flourish. I offered a home brew wood rot preventative solution earlier and will again (here) . As a long time sailor, I have used this and know it is effective.
I plan drip irrigation as well, but will be placing 55 gallon barrels to catch rain from the roof (via the gutters) during the winter to use for summer irrigation. If I can place them at 6 feet, I will have the head to go without a pump. I have not looked into timers yet but will.