Today I thought that I would talk for a minute about green roofing, specifically vegetative roofing. We have installed and consulted on green roofing projects over the years. Quite frankly, I think that they are really neat. Some of the benefits include…
- They help to eliminate water runoff into the sewer system.
- Provide a habitat for wildlife.
- Reduce the urban “heat island effect”
- Help to insulate the building.
- Can be very beautiful to look at.
Sometimes however, we run into things growing on the roof that should not be there!
This can cause major problems for your roof and your building. The roots of the plants can dig into your roof membrane, penetrating it and allowing water to enter the system. This can deteriorate your insulation and even your roof deck, maybe damaging vital contents inside your building. Dying vegetation such as leaves can sometimes clog your roof drains, not allowing the water to escape from your roof. This can add dangerous amounts of weight to your roof and potentially lead to roof collapse.
A properly designed green roof system takes these potential problems into account. When we have installed green roofs there is a root barrier that keeps the plant roots from penetrating the actual waterproofing membrane. Other elements of the system may include insulation, a high density cover board, a drainage layer, a water retention layer and a filtration layer. Here is a great example of what a green roof should look like. 
There is actually a HUGE difference between a Green roof and a roof with green stuff on it.
What do you have growing on your roof?
{ 3 comments… read them below or add one }
Joe,
Would love a guest article from you!! Just send me your blog article and the pictures and hyperlinks and I am happy to post it. Love, love pictures and real projects to talk about. Even if really old ones.
Thanks,
Linda
Sorry that it took a while to get back to you. We are swamped and I was out of the office for a week. I will work on getting these together for you.
Hi Joe,
like you we have been aware of the invasiveness of roots through membranes and are aware that the tiniest hole in a seam etc allows water through and hence the roots follow that water. Once they breach you have to basically start again. We have been using a spray applied Neoprene membrane for our projects which is homogenous having no seams or joins. Roots are not able to penetrate this membrane which means you protect both infrastructure below the membrane and above. The last thing you ever want is to be ripping up a green roof to find a leak. This product, WetSuit was developed in the States and is perfect for lightweight roofing such as Ply etc. Have you heard of this product and do you know of anyone using same in the States?