Tabletop green roof display with sedum plants and rain simulator at the UGA GSI demo site

Stop 3: Green Roof Display Table

Overview

A green roof is a vegetated layer installed over a waterproofing system on top of a flat or slightly sloped roof surface. At our demonstration site, a tabletop-scale model illustrates the layered construction and plant performance of an extensive green roof system using hardy sedum, yarrow, hyssop, euphorbia, and gaillardia species.
Practice Type: Rainfall interception and evapotranspiration

Quick Facts

ScaleTabletop display (3.5 ft. x 8.0 ft.)
Key PlantsSedum species (drought-tolerant succulents)
Best ForRooftops, covered structures, educational displays
Runoff ReductionUp to 60% or more of annual rainfall retained on roof surface
Cost Range$10 to $30+ per sq. ft. for extensive (low-profile) systems

The Problem

Conventional rooftops are impervious surfaces that shed virtually all rainfall as runoff. In residential and commercial settings, roof area often represents the single largest contributor to stormwater volume on a property. That runoff carries pollutants, causes erosion, and contributes to downstream flooding.

The Solution

Green roofs intercept rainfall at its source. The growing media absorbs water, plants take it up through their roots and release it back to the atmosphere through evapotranspiration, and the drainage layers slow any excess before it leaves the system. Even a shallow extensive green roof system can dramatically reduce the volume and velocity of stormwater leaving a building.

How It Works

The demonstration display uses a table-mounted model that shows both a conventional shingled roof surface and a green roof surface side by side. Rain simulator sprayers deliver water to both surfaces, allowing visitors to observe the difference in runoff behavior in real time.

Green Roof System Layers (Top to Bottom)

  • Plants (Sedum species selected for drought tolerance and shallow root systems)
  • Growing media (lightweight engineered soil mix)
  • Filter fabric (prevents fine particles from clogging drainage layer)
  • Drainage layer with water retention reservoir
  • Root barrier membrane
  • Waterproofing membrane
  • Roof deck structure

Design Specifications

The green roof system at the demonstration site uses LiveRoof’s RoofBlue RETAIN™, a planter module with extra storage space below the plants for rainwater. Excess infiltrated rainwater is stored in the reservoir, then wicked up through fabric back into the plant growing media and root zone.

Typical extensive green roof systems (those with a growing media depth of 6 inches or less) use lightweight engineered soil mixes and drought-tolerant plants that require minimal maintenance once established.

Try It Yourself

While full-scale green roof installation requires professional structural assessment, homeowners can apply green roof principles to garden sheds, carports, dog houses, and covered porches. Small-scale green roof kits and modular tray systems make DIY installation feasible for structures that can support the additional weight (typically 15–25 pounds per square foot when saturated).

Provided you have a strong roof and low slope, the extensive (low profile, large area) green roof installation costs can range between $10 to $30 per square foot. This varies based on the roof size, slope, required waterproof membranes, and labor costs. A 2,000 square foot residential roof project can cost between $20,000 to $60,000.

For Professionals

Green roof design requires structural load analysis, proper waterproofing specification, and plant selection appropriate for the local climate zone. The Georgia Stormwater Management Manual addresses green roofs as a source control practice. Consult with a structural engineer before specifying green roof systems on existing buildings.

Resources

Download fact sheets, design guides, and technical resources for this practice.