Step 7Building Brick
Fill the bottle with dirt and you have a brick. Dirt is a very cheap building material, but you usually need it to be a certain quality, with a proper sand/clay ratio. However, with the plastic bottles, you can build with any type of dirt. Use mortar in between the bottles, as with any other brick. Be sure to cover the ends of the bottles to avoid seeing them in the finished wall.
Alternatively, leave the bottles empty, or full of air. This will give the wall a better insulation value.
Leave a bottle exposed, and insert a solar garden light in the other end. Instant wall lighting.
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