Designing Sustainable Outdoor Spaces with Water-Absorbing Surfaces

Sustainable exteriors must be long-lasting and low maintenance. This means they have to be able to withstand extensive sun exposure and inclement weather with minimal resource intervention. One force of nature that can be particularly problematic is heavy stormwater runoff.

With myriad threats such as flooding, erosion, and toxic contamination, runoff has the potential to wreck landscaping and compromise the structural integrity of the building. Therefore, it is vital to design outdoor spaces with water mitigation in mind. Keep reading as we explore some of the most effective solutions for creating water-absorbing outdoor surfaces. 

Rooftop Gardens

The installation of rooftop gardens, green roofs, and other types of vegetated roofing systems is one of the most ambitious means of creating a sustainable exterior. Using a layer of vegetation on the roof’s surface in place of traditional roofing materials, green roofs offer various benefits to a building.

FACTS:

They provide shade for cooler temperatures, stormwater runoff management, and reduced greenhouse gas emissions. According to the EPA, green roofs are 30-40 degrees cooler than traditional roofs and can lower surrounding air temperatures by up to 5 degrees, making them one of the most effective solutions for combating urban heat islands. 

While rooftop gardens may be relatively simple (extensive) or complex (intensive), most systems consist of the following components:

• Vegetation layer - the visible surface that consists of grass, plants, shrubs, trees, and any other form of vegetation.

• Growing medium - the soil for the roots. Basic extensive green roofs that use only hardy plants may have a growing medium of just a few inches, while intensive green roofs that feature trees may have a growing medium of several feet. 

• Filter membrane - this is an essential layer for proper water absorption. It keeps the growing medium from clogging the drainage while allowing water to flow freely. It is typically made of a durable, lightweight, water-permeable fabric. 

• Drainage layer - this promotes the adequate flow of water off of the vegetated roof without damaging the substrate or the exterior of the building. 

• Root barrier - prevents root penetration and keeps the roofing substrate watertight.

• Thermal insulation - usually made from polyurethane or expanded polystyrene (EPS) foam, this layer limits heat transfer between the green roof and the building interior.

• Vapor barrier - this layer prevents moisture transfer between the rooftop garden and the interior. This is especially important in humid areas or areas with extreme temperature differences between the interior and exterior that are at high condensation risk.

• Structural support - reinforced beams, girders, and b-decking to handle the increased load of the rooftop garden.

While a vegetated roof does wonders for promoting drainage and reducing heat islands, it is also an aesthetically stunning addition that will boost property values and enhance the well-being of building occupants. 

Permeable Gravel Surfaces

Water tends to flow freely over sidewalks and concrete driveways. This presents an erosion threat to the surrounding landscape. It is also a potential hazard to the building’s foundation. To help mitigate the risks associated with runoff, permeable gravel driveways, sidewalks, and parking lots are a trending solution. The system works by installing a series of permeable pavers in the substrate.

These pavers can host gravel, stone, sod, or any other type of surface infill. By holding these surface materials in place, they eliminate the rutting and clumping concerns that traditionally mar non-gravel surfaces. In addition to being able to withstand heavy compressive forces, permeable pavers promote elite drainage, ensuring that water runoff does not threaten the building exterior. 

Outdoor Drainage Grates

Flowing water will always follow the path of least resistance. To ensure that this path leads in a desirable direction, it is important to install a series of outdoor drainage grates around the property. This will help manage surface water, prevent damage to landscaping, and reduce the risk of flooding.

While the grade and layout of the exterior will go a long way toward determining where to place the grates, some common areas include zero-threshold doorways, corners going around skimmer boxes, pool decks, and cultivated landscaping. 

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Below-Deck Waterproofing

Functional outdoor space is an important component of modern homes and commercial buildings. While the role of painting, staining, and covering decks and patios is widely acknowledged for preventing water damage, protecting the substrate is just as important. Unmanaged water beneath a deck can cause mold, rot, and corrosion that make the deck unsafe to use.

These types of water-related issues are also difficult and expensive to remedy. Therefore, it is crucial to take proactive measures to waterproof under deck surfaces. This can improve the durability, lifespan, and aesthetic quality of the outdoor space. Some of the best ways to control water flow beneath a deck include installing under-deck drainage panels, deck joist tape, and substrate moisture barriers. 

Enhance Your Exterior with Effective Water Mitigation

Uncontrolled water runoff has a number of consequences for a building’s exterior. Flooding, erosion, and toxic contamination are just a few of these. To help guarantee that excess water flow does not damage your property, consider the water-absorbing exterior ideas listed above and other resources at Structures Insider to stop water damage before it starts.