The expense of having a house collapse or constantly leak is what is too expensive to deal with when the setup is done by amateurs. If you can't afford professionals, then you can't afford to do the project at all.

Hi zaofangzi,

I would definitely get it designed by the professionals. And my reasons for that are green roof's take on a lot more weight than an average roof and even with the correct pitch a poor design can lead to drainage problems. Those two problems combined can make your exterior green roof an interior green mess. Keep in mind if there is a problem a lot of insurance companies will not cover the damage because something was not installed by professionals.

If you're handy I see no reason you can install and maintain this type of system. But I would try to find a company that has experience with green roof's and see if they are willing to help you throughout the process so you know it gets done the right way.

Hope that helps, good luck!