Concrete Raised Garden Bed Molds – Plastic ABS Portland Cement based Forms

Make a long-lasting rot-proof raised garden bed by casting your own concrete panels with these abs durable plastic molds. These concrete forms have a removable pipe that forms a hole in the overlapping end of the cast garden box wall. Rebar is inserted in the holes to pin the corners together either in a straight line or at a 90 degree corner. I’ve been making these wooden molds and casting these concrete garden box panels for around 10 years now. 5 years ago I made a video showing my first wooden mold design from plywood. In the years since I’ve refined and simplified the design in an attempt to make them easier to build, and to also experiment with making the panels lighter.
Not everyone who wants a raised concrete garden bed has the tools or ability to make their own molds. That’s where these new plastic forms come in. Now you don’t have to build anything at all. If you can add water to a bag of concrete mix then you can make these panels. Read the detailed blog post instruction writeup that details how easy it is to make a raised garden bed that will last a lifetime.

CONCRETE MOLDING INSTRUCTIONS: https://manabouttools.com/molds/

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I’ve been making these wooden molds and casting these concrete garden box panels for around 10 years now 5 years ago I made a video showing my first wooden mold design from plywood in the years since I refined and simplified the design in an attempt to make them easier to build and to also experiment with making the panels lighter not everyone who wants a raised concrete garden bed has the tools or the ability to make their own molds that’s where these new plastic forms come in now you don’t have to build anything at all if you can add water to a bag of concrete mix then you can make these [Music] panels some years ago I was involved with vacuum forming molds for making natural soap so I’ve had some experience with designing the tooling and the overall manufacturing process of vacuum forming so for a while now I’ve been kicking around the idea of making a plastic or a metal mold for these these concrete panels and I’ve been asked time and time again if I would sell the molds wood is bulky and heavy and expensive to ship but this thick ABS plastic is light and very strong so it’s the perfect fit for mail order these molds have the same dimensions and design as my first and second wooden molds they also have the removable whole forming pipe system as my fourth and simplest version that I came up with right now I have these in a 36 in and a 24 in length and these make a panel that’s 8 in tall by 2 and 1/2 in thick and the shape and size of the inset matches the first two designs as well with these plastic forms the castings drop right out no disassembly of the mold is required to allow for this the walls of the fors require a very slight draft or taper if you will the Finish panels and garden boxes look almost identical to my original ones if you’ve been making panels already then these new ones will also fit with the previous ones all right let’s mix some concrete and cast some panels but before I can mix concrete there’s some prep work to do you will want to have your mold sitting on a strong table or workbench that is level along the length of the mold as well as across the mold concrete is a liquid and we want the molds to be level and filled evenly if you don’t have a spirit level then there’s a level app on most cell phones or you can set a h or a ball on the table and see if it rolls away but a spirit level will come in handy when building the garden bed like all of my molds you’ll need to add some oil to the inside cavity I’ve always liked using food grade non-toxic mineral oil vegetable oil will also work but it can go rancid over time motor oil is another good option but I prefer not to have any residue of that near my garden a thin even coat applied with a small sponge or clean rag is all that’s needed don’t apply so much though that you end up with any puddles also apply oil to the pipes you’ll want to slide them in with the small hole sticking out clear of the flange edge of the form this small hole will accept a nail and give you a better grip on the pipe for removing it later when the concrete has solidified for this first pour I’ll just be using the standard Ready miix Concrete available at any building supply store as concrete mix is Dusty I like to mix it outside in a wheelbarrow then bring that into my shop to shovel into the molds it’s also winter here so I want the concrete to stay warm while it sets up I have 60 lb bags of concrete here and I need only 50 so I’ll leave some in the bag also this is good practice in case you add too much water and need to add more dry mix so I slowly add water while mixing and turning with the shovel I want the mix to be fully wet but not to settle like a wheelbarrow full of water when you shovel the mix it should still hold its Peaks it might take some practice if you’re new to Mixing concrete but be patient I’m sure I’ve said this before in other videos but I really like working with concrete I think it’s such an amazing building medium it’s very long lasting durable and rotproof and it can be formed in so many different shapes and for so many applications and for what you end up with it’s still relatively cheap especially when you consider the potential lifespan of whatever you’re casting in the shop I shovel some concrete into the form then I give the form a shake to settle the conrete into the corners you can further settle the mix and get trapped air to come to the surface by tapping the workbench with a rubber mallet I can and then add some more wet mix to top up the form a small Trel is Handy to spread the wet concrete around and toward the corners tap or vibrate it again then smooth it level with the top of the form you only want the form filled to the top or slightly below overfilling will make the panel too thick and may make the whole alignment off when you want to made it to another panel instead of a wheelbarrow and sh another way is to mix the concrete in a pale with a high torque heavyduty drill and mixing attachment some water is first added to the pale then the dry concrete mix and then mix it with the drill more water is added until you get a smooth wet consistency that’s not soupy here the second form is being Filled from the pale this does work but carrying the pale and pouring it into the form can be challenging for some so I prefer the wheelbarrow and shovel method myself I also like to use my reciprocating saw without a blade to vibrate the table to bring any trapped air to the [Applause] surface a light tring will give the inside surface of the panel a smoother finish and I also do that to make sure it’s level to or slightly below the top of the mold cavity when filled and traveled smooth and level I cover the forms with plastic I don’t want the concrete to dry much it under go a chemical reaction ction that generates its own heat as it uses the water in the mix to create strong bonds I like to keep my shop around 70° fah if it’s too cold it will take the wet concrete longer to harden in these ideal conditions the concrete should be solidified enough after 6 hours to remove the pipes I slide a nail into the small hole in the pipe and with a twisting motion I slowly extract the pipes I think there’s some resistance due to the plastic pipe rubbing against the hole in the plastic Mold Plus the pipe rubbing against the solidified concrete I designed the holes in the mold with a tight tolerance and to be just a few thousandths of an inch larger than the diameter of the pipe so the pipe has an interference fit it should stay in place but also be able to slide I wanted the pipe to make a seal when it’s inserted so no wet concrete would leak so the trade-off can be a little more effort when you go to remove them at this point the concrete is still moist and the pipes come out without too much effort if the pipes are really stuck then you can give them a gentle tap with a rubber mallet to free them followed by the twisting and pulling method this can happen sometimes if I wait longer than 6 hours or so to pull the pipes careful not to damage the end of the pipe hit with a rubber mallet you don’t want to flare the end and increase its diameter with that done I’ll cover the forms with plastic sheets again I like to leave the concrete in the forms for 2 days at least longer if your temperatures are cooler if you want to add more strength then you can embed some wire in the concrete in the form of a stiff wire grid down the middle I use some concrete mesh sections that I cut with small bolt cutters I also add a spiraling wrap of galvanized fence wire around the pipes you can wrap this wire around a section of larger diameter pipe first and I bend the sharp edges in for safety I run the pipe through the center of this spiral when I’m prepping my molds these additional steps are optional but they’re easy to do and not very costly I have a blog post link here for all the details of any additional items or tools you might need and for a few dollars more per bag you can buy high strength concrete mix and with or without this additional wire and grid I think it’s a good idea to upgrade your concrete mix to a high strength blend you end up with a stronger panel and a tough smooth finish I rotate the wrap wire upwards while I fill the form halfway then shake and vibrate it and this small Trel helps me get some concrete in behind the pipe where the wire wrap is then lay in the grid before topping up the form with more concrete instead of the wire mesh you could use a section of galvanized hog panel or some pieces of rebar laid down the middle so the first concrete por is sat for 2 days now we need to flip the molds upside down on our workbench it’s best to lift the mold from underneath and place the concrete against the the edge of the bench then slowly and gently rotate it over you don’t want to stand the form on its thin Edge or flange with 50 lbs of concrete in it now gently lift the ends in an alternating fashion to free the casting from the mold when pulling upwards on an end apply a little downward pressure with your other hand toward the middle of the form the casting should come out clean any excess oil on the concrete can be wiped away with a clean rag the mold can then be wiped down with a clean cloth to remove any concrete duster pieces and any leftover mineral oil I set the new castings on a thick plastic sheet on the floor of my shop I wrap the plastic up and over the top of the concrete panels like I was wrapping a present this will hold in the moisture so they don’t dry too quickly after a few days or up to a week I then pull them back up on the bench or set them over saw horses outside the vacuum forms have a small radius at the top Edge and this can leave a bump on the casting when filled right to the top after a week of curing this Edge can be removed or dressed with a concrete sanding block this will ensure your panels have no sharp edges this only takes a few minutes and it’s important to ensuring they fit together properly when assembling the garden [Music] box I use the smooth side of the rub brick when working around the ends and holes in the casting I want that inside corner to be sharp and free of any excess concrete alternative atively you could use a small concrete or masonry brick for this the process is identical for the 24in panels again I oil the cavity in pipes slide them into place mix some concrete and fill the molds halfway settle a concrete then top them up after 6 hours the pipes are extracted and the concrete is covered and left to harden further for a couple of days and I think I slightly overfilled these 24-in forms the only thing to note is is that the 24-in panels can take a bit longer to unmold the shorter mold length reduces the natural Flex of the plastic so it can take a bit more patience to free the castings I really like the smooth finish you get from casting in these plastic molds I have noticed a few more surface bubbles in some places though I’m speculating that the wood molds are porous so trapped air has somewhere to go whereas the plastic is a solid barrier to any air movement over inside one of our rainwater tanks I have a proper place to assemble the concrete panels and make a raised bed I already have a/ in waterline underground that’s secured to a wooden stake we had some squash growing in amount of soil here last year for this bed assembly I’ll need a level a framing square a rubber mallet and some 12-in long pieces of 3/8 rebar along with a shovel a grubber wheelbarrow and some sand I’ll measure and mark the approximate location of of the rectangular bed I’ll be using 6 36-in panels here I’ll use these 12-in sections of rebar to roughly Mark the corners then I’ll scrape away the dirt to make a shallow trench then I’ll scrape a bit more trying to get it pretty close to level now I’ll add a few few inches of sand to this trench fine crushed gravel would also work here as well I can then smooth it out and pack it under foot the sand or gravel will help hold the panels in place as you set the rebar in as these panels have that slight draft angle from the molds and the sand or gravel will give water a place to drain away if rain or irrigation water fills the holes in the panels then I’ll bring back the spe spirit level and scrape forward and back trying to get the sand layer as level as possible now I’ll bring in the panels and set the first one in place and adjust it until it’s level and set into the sand and I’ll bring in the second one and square it to the first and slide in a piece of rebar to pin the corner together the rebar should go in without any resistance if so check your hole alignment or wiggle the panels a bit to make them closer together it may seem overly fussy using a level and a square here but the panels are designed to go together when the corners meet at 90° and they’re all on the same level plane so I’d say it’s worth the effort to get them placed to right the first time and never have to worry about it again the third panel is aligned end to end with the second one and I’ll check that it’s in line and level my trench was a bit under sized so I had to scrape some soil away to fit and square the next panel to the first one then the fifth one is slid into place and rebar dropped in and a few more checks with the square to see if anything’s moved and measure side to side to see if the last panel will fit again I needed to remove a bit of dirt and add some sand as my trench on the end was a bit off with a final panel pinned in place I added a bit of sand around the Inside Edge before tapping the rebar into the ground with a rubber mallet I can now add add some soil to this raised bed from start to finish that took just over 20 minutes and here’s the square box using the 24-in panels so let me know what you think of these new plastic molds and if you have any questions leave them in the comments section Below in the next episode I’ll try a few lightweight concrete Blends in these new molds so watch for that coming right up also I have written stepbystep casting instructions on my website and I’ll put a link to that up here in the cards and in the description below all right that’s it for now we’ll see you next time