Yes, it is recommended to use a food grade liner to keep the moist soil separated from the timber of the raised garden bed.
A ModBOX garden bed does not need to be lined. As the wood is safe (not treated with anything) and water-resistant, the soil can be filled right alongside the wood inside the ModBOX garden beds.
We do provided a lining option which can come in handy if you do not want the soil inside your ModBOX to sit straight on top of the ground (for example, you may have concrete or a balcony and don’t want the water and leachates* draining out over the pavement or through your balcony). In these cases, we also insert an overflow at the bottom of the bed where the water can drain out at one central point.
The lining is also used when we install a Wicking System into a ModBOX.
The lining we use is made from Food-grade PVC liner and is custom-fit to the dimensions of your ModBOX.
*Leachates are simply small particles of soil and nutrients that may drain away with any excess water that runs out of the bed, thus creating muddy water.