Extensive or intensive green roof? Find out which one to choose

Green patios on underground garage slabs are becoming increasingly popular.

The surface of such a roof can serve as four different functional areas:

• relaxation area with intensive greenery
• children’s play area
• pedestrian and bicycle path area
• parking area

Each of these functions requires appropriate preparation of the substrate and layer layout, which is necessary for the proper functioning of green roofs and effective insulation.

Advantages of green roofs

It cannot be denied that there are many advantages to using green roofs, such as thermal insulation, which means that temperature fluctuations in rooms are not as high as in the case of non-green roofs, natural rainwater retention and a natural air filter that reduces dust and carbon dioxide.

Which bituminous felt to choose?

A thoroughly cleaned and primed garage slab should have a two-layer insulation made of bituminous felt with appropriate properties, such as a strong reinforcement and SBS-modified asphalt, so that the flexibility does not exceed -15°C. When designing the second layer of bituminous felt, remember to use a suitable root-resistant layer to minimise the risk of puncturing the waterproofing. Examples of suitable bituminous felt include NEXLER Green Roof PYE PV250 S50 or NEXLER Green Roof PYE PV200 S42.

Layer arrangement in an extensively planted green roof

Depending on the area of use, the roof should have an appropriate layer arrangement. An extensive roof is a type of green roof planted with natural vegetation such as grass, moss or herbs. The vegetation on such roofs does not require any special care or attention.

• Primed substrate (e.g. concrete with appropriate slope)
• Vapour barrier (e.g. NEXLER Alu S40)
• Bonding (e.g. NEXLER Styropuk Roof)
• Thermal insulation layer (non-absorbent, e.g. XPS, EPS boards, wool)
• Bituminous felt layer (underlay bituminous felt, e.g. NEXLER PREMIUM PYE PV200 S30 FF OR NEXLER PJ PYE PV200 S40 FF and bituminous felt resistant to root penetration, e.g. NEXLER Green Roof PYE PV250 S50 or NEXLER Green Roof PYE PV250 S42)
• Separation and diffusion layer (e.g. NexGreen Geo Safe 350)
• Filtration and drainage layer (e.g. NEXLER NexGreen Duo BB 20/200 P or NEXLER NexGreen Duo BB 20/150 P)
• Vegetation layer (which should include an irrigation system)