The long term health of a green roof is a subject that is often overlooked in the commercial world where value engineering reigns, sometimes at the expense of quality. In a world where buildings are part of asset portfolios which can be shuffled and sold multiple times, sometimes without the owner ever seeing the building, it is easy to see why extreme cost savings seem to take precedence.
Basic maintenance is something that isn’t treated as optional for many other parts of the building, but unfortunately when it comes to vegetation it can be treated as an unnecessary expense. On the positive side, some developers are now starting to appreciate that a good quality green roof adds real value to their property.
In the interests of projects like these, we have seen more people requesting maintenance plans and advice for the long term, and for domestic schemes particularly this will always be of interest. In this case, for high profile aesthetic roofs, it will always be the case that the roof will need slightly more maintenance than it would had it been primarily environmental.
Our plants and substrates for most commercial projects are designed so that the nutrition level will support the plants in the long term, with the nutrition gradually being replaced by a small amount of decaying plant matter. In highly overlooked areas however it might be desirable to add a small, very sparing quantity of fertiliser every few years if the plants start to look tired, just to provide a visual boost. However this should be used with extreme caution, and preferably after plants have filled in the gaps in the substrate – any increase in the substrate nutrition may increase the spread of weeds and grasses, so care should be taken to remove these if necessary.