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Matthew Lowe
Matthew Lowe

Green Roof Drainage Layer Buy

The green roof drainage layer mats are the ideal roof drainage solution. This 3D mesh mat enables water to quickly drain and prevents pooling. Each drainage layer mat is applied over the rooftop surface and provides a protective layer that enables both drainage and breathability of roof membranes. These mats are perfect for green roof projects as they enable water to continuously discharge even under heavy compressive loads. The geocomposite wrapping over the nylon mesh media core prevents dirt and debris from clogging the drain and filters out any litter or debris. The green roof mats are very popular in the following applications: vegetative green roofs, rooftop gardens, under artificial turf, permeable paver base, and as a protective layer over roofing membranes.

green roof drainage layer buy

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A green roof drainage layer is usually an HDPE (high density poly ethylene) membrane that stores water in cups so that plants can draw on it in times of need. Whilst excess rainwater passes through perforations between the storage cups.

Given that the primary function of a green roof is rainwater management, the means by which it drains and stores water are a more appropriate form of categorization. While the descriptors above are legitimate ways to characterize a green roof, they do not speak to its function.

Green roof components with capillary properties can help move water from wetter areas to drier ones to even out moisture differentials naturally. Instead of waiting for water to be drawn up vertically via evaporation exclusively, capillary materials allow water to move horizontally, as well. This makes better use of finite water resources and balances soil moisture levels across the many microclimates of a green roof. Capillary action proves to be an elegant way to manage water levels across a green roof without irrigation controls, timers, sensors and related systems.

There are four primary material types used in the drainage layer: molded drainage, entanglement sheets, granular material and structural drainage. In the next section, we will take a closer look at each.

Drain plates need to be overlapped during installation to create a monolithic drainage layer. In a perfect world with no thermal expansion and contraction, no building movement, no wind, no freeze/thaw cycle and no plant growth/change, it would not be necessary to nest drain plates on top of one another; but in reality, there are a number of physical forces constantly trying to push these materials apart. Any movement could result in soil movement down to the waterproofing membrane, potentially causing abrasion, erosion and drainage compromise. So, maintaining that monolithic drainage layer is paramount.

While they offer strong sheet flow, molded drainage materials cannot move water in their cups across the roof by capillarity due to their hard, plastic composition. Water residing in cups is only available to soil and plants directly above or within a few inches of the cup and cannot be accessed by plants farther away.

Contractors tend to enjoy working with entanglement drainage because it rolls out readily and is easy to install. Building owners also love entanglement sheets because they are relatively inexpensive (though slightly more expensive than molded drainage materials). Entanglement drainage also offers better aeration below the root zone than molded drainage layers.

Because of the way this material absorbs water versus simply storing it like other materials, granular drainage cannot handle incoming runoff well. It also does not possess good sheet flow and tends not to drain rapidly. To help water flow where it needs to go, contractors will often install a slotted channel (or drainage conduit) in the granular drainage/capillary storage mat layer of a green roof assembly. During a heavy rain event, there will be a pressure differential between the water in the drainage media and the air in the slotted channel, so the water will shoot into the channel, through a network of drainage conduits and then be routed to a roof drain box. The conduits snap onto these porous roof drain boxes, which are located across the rooftop and allow water to flow off the roof while keeping debris out of drains.

Granular drainage media is typically applied on a rooftop from a giant bag that is generally suspended by a crane. It is slit open and moved around, pouring onto already-installed capillary mats, where it is spread around by an installation team. Once it is evenly spread, 2 or more inches of filter fabric are added on top of the drainage media, then soil/growing media and plants are added. The finished product might look something like Figure 6.

Figure 7 shows another example of a granular drainage/capillary storage roof, though this one serves a slightly different purpose. Instead of pavers preserving the water supply, this green roof intercepts and detains some incoming runoff from a higher nonvegetated roofing section. The water comes down the downspouts on the left during storms, showcasing that green roofs can help control rainwater runoff even beyond their actual footprint.

We often see this stacking occur closer to roof drains where water tends to pond and roofs slope downward. The structural height of the drainage media gradually increases closer to the drain, maintaining and leveling the growing bed on the surface of the green roof while providing necessary water storage near the drain. Figure 9 shows an example of this setup: the drainage media on the far right might be 3 inches deep while the media on the far left, near the drain, is more like 6 inches deep to suit the ponding depth in that area.

Structured drainage can also be paired with pedestals that are designed to hold up concrete pavers on rooftops. Depending on height requirements of your weight-bearing materials under the pavement, structural drainage media or pedestals could prove to be the more cost-effective option for enabling ponding and maintaining the structural integrity of walkways. In either case, you will need some sort of drainage media in place. One thing to keep in mind is that construction of the sort of natural-looking, meandering pathway you see in Figure 6 is not possible with pedestals, as they require rectilinear, uniform pavement geometries to function properly.

Green Roof Solutions offers many different drainage layer options, depending on system goals regarding water retention. The most critical role of the drainage layer is to provide an adequate flow of water off the roof during and after rainfall. The design of the different drainage layers allows for a portion of the stormwater to be retained above where the water is allowed to flow freely off of the roof. The systems are designed to ensure that stormwater can be used by plants for longer periods of time without oversaturation of the system. This promotes plant growth, avoids anaerobic soil conditions, and keeps retained water from pooling on the roof.

GRS drainage products typically fit into a green roof system above the GRS Root Barrier and below the GRS filter fabric. Depending on regional precipitation rates and the water retention goals for your specific project, Green Roof Solutions has a full range of products to meet your needs.

GRS Extenduct is a 40% recycled drainage core in a waffle pattern with a geocomposite fabric bonded to the top side. The design creates an open and continuous flow path, even under high loads. The filter fabric top layer prevents clogging from the growing media, and the waffle entanglements sit directly on the root barrier.

It is used for the water retention of green roofs.Bauder Mineraldrän BS 2/11, L 2/11Materialslatevolcanic rockWater retention capacityAb. 15 Vol.-%Ab. 15 Vol.-%Volume weight when wet630 kg/m930 kg/mVolume weight when is saturated with water780 kg/m1050 kg/mCompaction by transporting and construction5 %10 %Bauder Mineraldrän BS 2/11 is delivered in bags of 60 l. Item number: 7412 0000

Water drainage element for roofs with vegetationBauder Dränelement NF 10Pressed foil made ofHDPEWeight of pressed foilabout 620 g/mFiltration veil made ofPPWeight of filtration veilabout 130 g/mThickness10 mmTotal weightabout 750 g/mCompression strength400 kN/mDelivery formRoll of 25 mItem number7468 0010

It can be used for light, planted roofs. These elements have low retention capacity. They have to be mounted linked to each other and floating over the protective layer of the waterproofing. Together they form the drainage layer of the extensive green roof.Bauder Drän- und Speicherelement DSE 20MaterialHDPESize1,06 x 2,36 mHeight20 mmWeight1,2 kg/mWater retention capacityabout 7,4 l/mDelivery formPanel of 2,5 mItem number7468 0020

It can be used for light, planted roofs. These elements have medium retention capacity. They have to be mounted linked to each other and floating over the protective layer of the waterproofing. Together they form the drainage layer of the extensive green roof.Bauder Drän- und Speicherelement DSE 40MaterialHDPESize1,04 x 2,03 mHeight40 mmWeight1,8 kg/mWater retention capacityabout 13,5 l/mFilling volume21 l/mDelivery formPanel of 2,1 mItem number7468 0040

These elements have high retention capacity and can be used for extensive and intensive green roofs with car traffic, heavy vehicles etc. They have to be mounted linked to each other and floating over the protective layer of the waterproofing. Together they form the drainage layer of the ecological roof.Bauder Drän- und Speicherelement DSE 60MaterialHDPESize1,0 x 2,0 m (covered area 975 x 1975 mm)Height60 mmWeight2,0 kg/mWater retention capacityabout 17 l/mFilling volume33 l/mDelivery formPanel of 2 mItem number7468 0060Even in the early design stage of a rooftop or terrace ecological construction, we can advise you in order to choose adequate elements for your investment. 041b061a72


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