Is it possible to use regular topsoil on green roofs?
Regular topsoil is not recommended for use on either extensive or intensive green roofs. The most important characteristics of a green roof substrate are good water permeability and high maximum water capacity. Both of which are often low in topsoil. Some topsoil may have better water permeability and retention capacities than others; however, the variability in quality is high and relying on topsoil is risky. Other problems for vegetation when using topsoil is dryness; topsoil gets especially hard when dry and can damage plant roots. The issues mentioned above can be amended by adding organic content, however, this could compromise the fire resistance of the substrate. In comparison to the mineral substrates which are normally used for extensive green roofs, topsoil has low water permeability, low water retention, much higher weight and less suitable chemical and physical properties. In addition, the contamination from weeds and pests creates competition for drought resistant plant co
