How to Build a Grow Box Step by Step

So you have selected your site, decided what size of grow box you will be constructing, and gathered your tools, equipment, and materials. You are now ready to construct your grow box.

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STEP 1 - Leveling the surface

If the base of your box is a concrete or asphalt surface, chances are it is already level. If however, you are using a dirt surface then you will have some work to do.

Using a garden hoe, a garden rake, and any other garden tools you feel are necessary, level the surface for the base of your grow box by removing all weeds, rubble, stones, etc. Break up any large clumps of soil. If necessary, you may want to add some sharp sand or plastering sand to the area to help make the base of the grow box nice and level.

When you have completed your task, the surface for the base of your grow box should look something like this:

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STEP 2 - Marking out the area

You must mark and measure the area for your grow box construction to ensure that you have adequate space for the grow boxes as well as your pathways. 

If you are building your grow box on a dirt area then: 

Using your tape, stakes, square, and lines (string/twine), mark out the area where your concrete blocks will be placed and where your pathways will be located. Where you will be placing your concrete blocks will be determined by the size of the grow box you are building. If you are constructing more than one grow box in the same area, then your pathway should be wide enough to allow a wheelbarrow to pass comfortably (ie. approximately 2 feet wide).
Your concrete blocks should be placed outside the marker lines to get the correct size inside the grow box. If, however, you are planning on placing your blocks on the inside of the lines then you need to measure an extra 6 inches on all sides of the grow box to accommodate the width of the concrete blocks.

The lines should be level and square and should be at a height of eight inches from the base of the grow box. This is done to accommodate the height of the concrete blocks and will allow you at the same time to be able to ensure that the top of your grow box is nice and level. If you are constructing more than one grow box then you need to mark out the entire area before beginning to place your blocks.

If you are building your grow box on a concrete or asphalt surface then you will need to mark out the area using chalk lines as there is nowhere for you to pound in stakes for tying string. When building on this type of hard surface you will have to use your spirit level to level your concrete blocks 

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STEP 3 - Measuring and setting down the plastic sheeting

Plastic sheeting or weed barrier is only necessary if the base of your grow box is on the soil. This plastic sheeting will prevent weeds from growing into your grow box from underground. Find a large open area so that you can spread out the plastic comfortably. This will allow you to measure and cut the plastic neatly and accurately. The plastic sheeting should be cut a few inches larger than the size of your grow box so that it extends beyond the external "walls" of the grow box. This way you can be assured that the grow box has a level base and all excess water will be able to run off easily. The edges of the plastic can later be covered over with sharp sand or pebbles to enhance the aesthetics of your grow box area.

Measuring and cutting the plastic sheeting before setting it down on the dirt area.

Setting down the plastic sheeting on the levelled dirt area.

Plastic sheeting has been set down in the area which was previously measured and marked out for constructing the grow box.

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STEP 4 - Placing the concrete blocks
Your concrete blocks will be placed closely together. No cement will be used as the spaces between the blocks will allow excess water to drain through and prevent waterlogging. As mentioned earlier in this post, your concrete blocks could be placed outside of the marker lines to get the correct size inside the grow box, or your blocks can be placed on the inside of the marker lines.

Blocks placed inside marker lines

Blocks placed outside marker lines

When placing your blocks, your marker lines will be used as a guide to ensure that the height of your grow box is neat and level, however, you should still use your spirit level to check the level of your blocks as you go along adding your concrete blocks. This will ensure that your grow box has the same height all around. After having put in all that hard work, you do not want your blocks to be bent, leaning or wavy.

Remember in the end you want your grow box to be aesthetically pleasing.

Since your grow box does not require that you use cement to secure the concrete blocks, then when placing your blocks on the plastic sheeting, a small amount of sharp sand can be used to build up blocks that do not meet the eight-inch height on the marker line. The sharp sand is used since it will allow excess water to drain freely out of the grow box.

 

If however, you were able to level your area well, then there may be no need for using sharp sand to level the concrete blocks. Another option if you do not want to place sharp sand on the plastic sheeting, is to add the building/plastering sand under the plastic and level the blocks as you go along.

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Squaring the corners of the grow box

It is important to ensure that the corner blocks of your grow box are "square" (at a 90-degree angle to each other). If this is not done, especially when you begin constructing, you could end up with the problem of your concrete blocks not connecting when you get to the far end of the grow box.

Use your construction square to ensure that your corner blocks are at 90 degrees

The "one in one out" pattern below can be used to control the size of the grow box. If you want the five feet width inside your grow box and you are using four blocks for the width, then this is the design you want to use.
It also helps to "tie in" the corners of the grow box and make the blocks more secure.
Remember no cement is being used.

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YOUR CONSTRUCTED GROW BOX 

 Here are some examples of what your end product should look like. As you can see if your grow box is being built on a solid concrete surface, then you would have less work to do to make your grow box look neat and level.

  Some examples of Grow boxes constructed on a soil surface.

Example of a Grow box constructed on a solid concrete surface.

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PATHWAYS

Make sure that the pathways between your grow boxes are properly prepared and clear to ensure easy access to your grow boxes and to prevent accidents. If your grow box is constructed on a dirt surface, the pathways should be kept free from weeds, stones and rubble.