Building a green roof with flagstones and ground cover

Asked July 9, 2020, 8:21 AM EDT

Hi there, I live in Washington, DC and would like to install a green rooftop on the 4th story of my house which is fully exposed. I am having my deck rebuilt on the rooftop and I would like to install (instead of deck boards) some sort of material that can hold soil and plants, to make a green roof of sorts. I’d like to be able to walk on these plants and I assume they would be some sort of drought resistant succulents, but I’m not exactly sure. Can you suggest for me the best process I can recommend to my carpenter to have him construct something that will be 1) effective with minimal maintenance and 2) will last a long time ? I need to tell him exactly how to build the structure to hold the soil / plants so any information you provide me would be wonderful. Thanks. Best, Kevin W

District of Columbia County District of Columbia

1 Response

Hello Kevin,

Given the importance of proper design with regards to materials choice, structure weight ratings, moisture control, and plant selection based on substrate depth, we suggest you find a landscape architect or firm with green roof experience to work with, as this is a niche and very specialized field and not our area of expertise. D.C. encourages green roof use and likely has multiple firms/individuals serving the area from the city as well as VA and MD. Here is one search page from the Landscape Contractors Association where you can select a "green roof" specialty area in the search criteria: https://www.lcamddcva.org/search/custom.asp?id=3812. Here too there is an options for "green or vegetated roof" from the Chesapeake Bay Landscape Professional directory search page: https://certified.cblpro.org/

A number of groundcovers do not tolerate regular foot traffic well, including the more fragile succulents. That said, you can ask for a design that incorporates either walkable groundcovers (if suitable) or an unplanted pathway through the beds. This will also limit soil/media compaction which is a detriment to root health.

Miri