Thursday, October 2, 2008
Florida Green Roofs - Prepping the mat with expanded mineral material - perlite, vermiclite, expanded clay, agar, trace minerals, and more!
Episode Three - prepping the planting base - prepping the mat. Lots of standards and regulations, common sense precautions and just plain good BMP's - Best management Practices come into play now that the mat is rolled out. So we've talked to death the reason why we don't like trays and modular systems....Hey I heard of a roofing company somewhere is South Florida who just installed a system of trays on their roof - and the plants died...
But the reason we choose mats is not the reason we don't use trays. The reason we choose mats is because with a mat, the green roof's plant roots can grow as far north, south, east or west they want to grow. No circling (as in trays) and no self strangulation in a couple of years (as in trays).
Sure - maybe Plant A will Run into Plant B. Instead of root circling and strangulation though, the roots will compete with each other and the stronger plant will go onto to survive. The important note here is that there is always coverage - though one may dieback, the stronger or more suited plant survives. The mat advantage has proven itself on the Dearborn, Michigan Ford Motor Company 10 acre roof.
OK - back to the soil...
Wouldn't it be easiest just to fill the mat with dirt from the backyard? - Maybe so - but I wouldn't do it. Think of the weeds, nematodes, fire ants, etc you may be digging up and placing on your roof.
Moreover, ASTM has specifications written for dust and organic matter and more for green roof soil systems. The MetroVerde engineered soil (MV GRP) mixture we use is a proprietary blend - and we add soil goodies to it! I think of it as a stabilized outdoor hydroponic system!
So lay out a piece of plastic sheeting on the ground in an area you won't be walking - please note that if you have outside cats or dogs - they love to use a rolled mat system as a huge litter box! Take precautions!
Roll out your mat on top of the plastic, add the mixture of perlite, vermiculite and expanded clay. Apply the tackifier initial layer. Sow desired seeds or installed pre-grown plugs and reapply tackifier.
We'll explore soil mixtures and tackifier solutions (there are many of these sticky mixtures) in an upcoming post. In the meantime - Happy Green Roofing!!! Kevin