This is an older post that I published in 2008 after extensive research into earth construction. I have always had a sincere interest in methods of construction that are harmonious to the environment and derived much of this knowledge after a year of trial and error using different techniques. I purchased a large earth brick making machine from India in 2008 and went on to discover my own method for earthcrete construction after running into labor shortage as it took 10 people to operate the machine and it did not make financial sense in the long run to continue operation. It was an expensive lesson(10k). However while experimenting, I derived a formula for cast-in-place construction, that was very successful and looked 10x better than the earth-bricks.
I apologize that some of the photos are missing, this post was recovered from a backup and somehow I seem to have lost the photos in the process. I will re-post them once I uncover their mystery location.
Step 1 Materials & Tools
you will need the following materials:
- 4 – 1″x 4″x 8′ pieces of wood – scrap wood may be suitable
- small box 1.5 inch screws
- 1 roll welded wire mesh (for reinforcement)
- 3 or 4 bags – Portland Cement
- large pile of dirt
- gravel (recommended but optional – adding gravel makes your earth pavers stronger)
and these tools:
- circular saw or hand saw
- 10 or more concrete stakes (if you dont have these, you can make your own with sticks of wood. just cut a pointed end on some scraps of wood at least 1 foot long)
- medium size level (any size will work though but a 2 foot level is easier to maneuver around the stakes)
- builders square
- finish trowel
Step 2 Planning
It is important to draw a simple layout of how you want your earth pavers to look. Do you want them all to be the same size, or random sizes like in this example? The thickness of the wood will be the final separation distance between the pavers. If you want a bigger separation, use thicker wood like a 2×4 which will give you a separation distance of 1.5 inches.
After creating your drawing, you need to define a starting point for building your first forms. It is often easiest to choose the center as a starting point for larger patio installation however if you are creating a walking path, then starting at the first edge and working your way down the path seems to work best.
Step 3 Building your forms
Cut 4 pieces of wood to your specific dimensions. It is important to cut your wood with perfect square. Use a builders triangle or square to mark your lines and be careful with your cuts(more on this later). You can also use a miter saw set to 90º to make these cuts if you are unsure of square. In this example all of my pavers are rectangles so I cut random lengths of wood in “pairs”, but if you are making square pavers then you will cut 4 pieces of wood almost the same size but remember to add 1.5 inches to the length of 2 pieces to account for the width of the wood (in this case 3/4 inch). The negative space in the center will be the exact size of the paver, and for my example, I dont worry about lengths of wood because I want to create a random pattern. I simply make sure to cut my pieces in pairs.
Once you have cut some boards, you are ready to begin assembling the first form. Start by screwing together 2 boards with 2 screws in each corner. Continue to assemble the 4 pieces so that all 4 corners are attached securely. Do not use large screws for this as it will be much harder to remove them once the paver is poured.
Pick the starting location for you first form and put the form in place. Choose a corner and drive a stake in the ground securely a few inches from the corner. Using 1 screw, attach the stake to the form. Carefully, using the builders square, position each corner by driving stakes on opposite sides until the stakes are squarely positioned around the form. At this point the form is square but not level. Put the level from corner to corner on the form starting with the corner that has the first screw and level the form with this corner by attaching a screw at the level point and continuing around until the entire form is level. Your first form should like something like the picture below:
In this example, I am pouring multiple forms at once (5) and have assembled each successive form to connect to the starting form. To do this, it is only necessary to attach 3 pieces of wood to the first form. Always make sure that your wood is attached squarely and check your square regularly with the builders square. Remember how I cut the pieces of wood in pairs? The matching piece can be used to keep your dimensions by inserting it between the two sides as you are attaching them to the form. The picture below shows an example.
Do NOT attach the next form pieces by screwing from the inside of the first form. Make sure to attach the successive forms by screwing from the top edge at an angle down into the form side that is being attached (see picture below). This will make it so you can remove the forms. The most important thing to consider when assembling your form pieces is how you are going to remove your forms. For instance, if you assemble many forms like I am doing in this example, pouring 5 pavers at once, then it becomes critical to never cover a screw with your mix. Doing so can have disastrous consequences like breaking your freshly poured pavers because you cant properly disassemble the forms.
Always leave the outside corners of the first form exposed when choosing the location of each added form. Once again the thing to consider here is how to take this thing apart once complete. In this example, using random sizes makes it easy to position a number of successive forms onto my first form because the first form is considerably larger than the others and gives me wiggle room to attach my forms without covering up screws. Notice in the picture below how the larger center form (the first) has all its corners exposed.
Youre final form assembly should look something like the following:
step 4 Compacting the ground
Your forms are in place, now it is time to compact the earth to keep your pavers from sinking irregularly. To do this, surround your form-work with a small amount of dirt so that water can not run out. Now, using your hose completely saturate the ground inside the forms. Take care to not let the water dig a hole by moving the hose around with your hand like waving a wand. Let the water pool up in each form then let it sit until the water completely drains into the earth below. Depending on your soil conditions, repeat this step until the ground is compacted. Alternatively, a hand rammer can make short duty of the task but must be small enough to fit between the forms.
When using water to compact the ground, make sure that the earth piled up around the form doesn’t blow out (it probably will), if it does then just scoop some more dirt into that location so that the water doesn’t pour out underneath.
step 5 Reinforcement
Take the welded wire mesh and using wire cutters, cut a piece that will sit in the center of each form. Leave 2-3 inches around each side. The goal is to have the reinforcement suspended in the center of the earthcrete. Once you have all the pieces ready, remove them and set them to the side so they are easily accessible.
step 6 Mixing earthcrete
Once your forms are complete, the ground is compacted and reinforcement ready… now it is time to mix EARTHCRETE!
Most people will probably just mix the materials by hand in the wheelbarrow. This is totally fine but gets tiring really fast. For medium size projects, I recommend buying a small portable concrete mixer. These work well for mixing earth and can save you a lot of time and energy. The one I am using is 3.5 cubic feet and they sell them at home depot for around $150. Another benefit of using the powered mixer is that it is much easier to achieve a homogeneous mix. Then again, i did ALL my early experiments the old fashioned way, by mixing everything in the wheelbarrow and its kinda fun so don’t worry if you don’t have a mixer. Just go for it!
Gather your mix materials around your mixing container of choice so they are readily accessible. Bags of Portland cement are usually 94 pounds and quite heavy. Keep these close but make sure they don’t get wet during the mixing. You should have a large pile of earth, pile of gravel(optional), bags of cement and the hose nearby.
Now use the following formula for making your earthcrete mix
(courtesy of Isaac Horton, Earth Architecture™):
- earth/subsoil (sifted)- 3 parts
- gravel – 2 parts (use of gravel is considered optional but makes stronger pavers with a slightly higher compressive strength)
- cement – 1 part
Mix all ingredients together before adding water. Add water while mixing taking care not to put too much in. The right amount of water is easy to determine by observation. Basically you want the mix to be pourable without being soupy. It should be something like the consistency in the pictures below. Learning to add the correct amount of water will make your job easier in the next step.
step 7 Pour it
If you are using a mixer, transfer the mix to the wheelbarrow. Take the wheelbarrow to the forms location and begin scooping the mix into each form. To begin, only fill the forms halfway and then put the piece of wire reinforcement on top of the wet earthcrete mix and continue to fill each form. You should now have the wire suspended in the center approximately. This will make your paver much stronger and less prone to crack later.
As you fill the forms with the earthcrete mix, take the shovel and jab it into the corners making sure that the mix goes into every crevice. Especially with gravel, the mix will tend to create pockets of air especially in the corners so jab them good with the shovel until you feel sure that you have it densely filled. fill to just above the level of the top of the wood form.
Grab a piece of wood a little longer than the length of your forms. This will be your “screed”. Now drag the screed across the top of the form in jiggly motion. You want the mix to be perfectly even with the top of the form. As you pull the screed, make sure that the mix penetrates to the sides and corners, and scoop out or push off excess mix into surrounding form spaces.
Continue to pour and screed until you have exhausted your mix. Keep mixing, pouring and screeding until you have filled all the forms completely.
step 8 Trowel finish
How you finish the top is somewhat of an artistic choice. There are a few options, but I prefer to trowel finish each paver and give it somewhat of a custom hand worked look. I also choose to push down the sides and corners slightly (about 1/2 inch) to create a rounded top on each paver. (See pictures below) For a more square look similar to a sidewalk, just use the trowel to smooth out the top letting it rest on the tops of the forms as you drag it across.
step 9 Curing
After troweling, it is time to kick back and let it cure for 18-24 hours. I’m often pulling forms apart first thing in the morning, so overnight is acceptable once you get a feel for it.
step 10 Removing forms
To remove the forms, first take out all the screws with the screwdriver. Now remove the stakes. pull all the outside forms off first by peeling them away from the earthcrete. These ones will come out very easily. Now you are left with the forms that are stuck between pavers. Very carefully, use a hammer to tap the forms slightly and break the bond. Only hit it from the edge, making sure not to stress the freshly poured earthcrete. Use the claw end of the hammer to pull up on the form delicately but with force and intention to go perfectly straight up. If you lose balance or pull against the sides of the pavers, they will break because they are still very fresh and “green”.
step 11 Clean edges
After removing the forms, there are some jagged edges. First use the trowel to lightly scrape each edge and remove the jaggedness. Now, put on a pair of heavy duty gloves and rub the edges gently until you get the desired amount of roundness. Remember to be gentle as the mix is only just begun curing.
Earthcrete and other stabilized earth mixes continue to harden as they age. I dont recommend walking on them for at least 2 weeks and even better if you can wait a month.
step 12 Stain it, seal it
Because earthcrete is stabilized with Portland cement. It turns gray. This is an unavoidable outcome of using cement and since we want to enhance our earth pavers to look at least as cool as a concrete paver, we recommend staining them with a high quality acid stain. I use “Blush Tone” acid stains made by Brickform. This product is made for concrete but has excellent results on earthcrete as well. Alternatively you can mix oxides in the mix for a “flatter” color and these are available at concrete supply stores in colors like red, yellow, brown etc.
Whatever your choice of finish, you may want to preserve the color with water based penetrating sealer. There are some great new “green” options for sealers so look around and choose the one that suits you best. I use different sealers for different jobs, but recommend the new soy based sealers as they are environmentally friendly and work great! Here is a link to some good stuff.