✅ Lining the raised bed with foil » This is how it's done

Damp wood rots quickly
Which films are suitable for lining a raised bed
Lining the raised bed with foil - this is how it's done

In the instructions for building raised beds, you often read about lining the bed with foil. The purpose of this is to protect the wood from moisture and thus help the bed to live longer. However, not all films are suitable for this.

The film protects the wood from moisture

Damp wood rots quickly

The substrate in a raised bed should always be as moist as possible and not dry out. Wood, on the other hand, must never come into contact with damp soil, otherwise it will quickly rot. You should therefore always set up such a bed in such a way that the lower edge can dry off quickly after a downpour. Ideally, your raised bed will have a plastic or metal profile to protect against soil moisture so that the wood does not come into contact with the soil in the first place. If this is not the case, you can also place the bed box on a row of slabs or stones. Protect the inner walls of the raised bed with a robust foil.

Which films are suitable for lining a raised bed

Water-permeable fabrics such as fleece are not suitable as bed linings because there is a complete lack of protection against moisture. Rubber, PE and PU foils, which are normally used for pond construction, are suitable for this. Above all, pond liner, which has to hold off large quantities, is ideally suited for this purpose: it is very robust, tear-resistant, absolutely waterproof and rot-resistant. If you want to use pieces left over from pond construction, the individual strips should overlap by a good ten centimeters at the seams. Dimpled foil specially made for the construction of a raised bed can also be used. This usually has the advantage that - in contrast to conventional pond liner - it is free of harmful plasticizers. The knobbed foil is also used for drainage, as excess water is drained along the bed walls.

Raised beds that do completely without foil

The sole purpose of lining the raised bed with foil is to protect the wooden bed box from moisture damage. Of course, such a protective measure is not necessary for all raised beds: beds made of high-quality aluminium, corten steel or stone, for example, usually do not need an additional lining, as these materials are more or less resistant to moisture. Plastic doesn't really need a lining either, but attaching a (harmless) film makes sense here for other reasons. Plastic often gives off harmful substances to the substrate, so that a film is interposed to protect against this.