A green roof is a section.
A green roof is not a finish. From above it is a lawn and from the street it is a parapet; what makes it a green roof is the 45.7 centimetres of section running from the sedum down to the structural slab. This page opens that section layer by layer.
Downwards,
forty-five point seven centimetres.
As you scroll, the cut line descends. Each layer names itself — its thickness and its job — the moment the line reaches it.
- 01
Vegetation
30 mm
Sedum-based extensive planting. The living layer that shields the roof from sun, hail and thermal shock.
- 02
Garden substrate
120 mm
Lightweight engineered growing medium. 6–20 cm for the extensive planting in this section; up to 40 cm for intensive planting.
- 03
BTM Green system filter
1 mm · 110 gsm
SF 32 filter fleece. Lets water through while stopping substrate from migrating into the drainage layer.
- 04
BTM Optigreen FKD 25 drainage board
25 mm
Drainage board with water-retention cells. The perforation sits at the second step, so water stays in the cell — 25% more water and energy saved than boards perforated at the lower step. Compressive strength 250 kPa.
Drainage board — View product - 05
BTM Green moisture-retention mat
3 mm · 500 gsm
Protection and moisture-storage layer. Shields the waterproofing from mechanical damage above.
- 06
BTM Botanik Elastobit PE4
4 mm
Root-resistant bituminous waterproofing membrane. The first membrane in Turkey to carry a TS EN 13948 root-resistance certificate.
BTM Elastobit — View product - 07
BTM Elastobit PE3
4 mm
Polyester-fleece reinforced base membrane. The first layer in a two-ply build-up.
BTM Elastobit — View product - 08
BTM Bitümer primer
0.2 mm
Bitumen-based primer that prepares the concrete for the membrane. The thin film that makes it bond.
- 09
Screed to falls
70 mm
The sloped layer that carries water to the outlet. A minimum fall of 2% is formed.
- 10
Structural slab
200 mm
Reinforced concrete deck. Carries the entire dead and live load of the green roof.
A green roof is built because it measures,
not because it looks well.
The figures below come from BTM Optigreen technical documentation. Each rests on a measurement; aesthetic arguments did not make the list.
Fuel saving
The substrate and plant layer cut heat loss
Sound insulation
Substrate mass and plant texture absorb noise
Dust capture
The planted surface traps airborne particulate
Extra water and energy saving
Compared with boards perforated at the lower step · FKD 25 / FKD 40
Rain falls, the roof holds it.
Bare roof
All of the rain runs off the surface at once and reaches the outlet. In heavy rain the whole load hits the drainage network in one go.
Green roof
The planting and the water-retention drainage board hold part of the rain; the rest leaves with a delay, and what is held evaporates and cools the surface.
- The waterproofing is protected from UV, hail and thermal shock, so its service life is extended.
- Rainwater is retained, easing the peak load on the drainage network during heavy rain.
- Creates habitat for birds and pollinating insects inside the city.
- Adds usable recreation space.
- Produces oxygen.
- Can share the same roof with photovoltaic panels.
The structure speaks first,
the planting is chosen second.
What determines the green roof type is not the plant but the dead load the slab can carry. Load grows fast as substrate depth increases.
Extensive
Substrate depth
6 – 20 cm
Dry weight
60 – 150 kg/m²
Sedum-based, minimal maintenance. Non-trafficked roofs.
0 – 500 kg/m² dead load
Semi-intensive
Substrate depth
15 – 25 cm
Dry weight
120 – 200 kg/m²
Grass, herbaceous plants and small shrubs. Limited use.
0 – 500 kg/m² dead load
Intensive
Substrate depth
25 – 40 cm
Dry weight
200 – 500 kg/m²
Roof garden. Trees, seating areas, walkways.
0 – 500 kg/m² dead load
Change the pitch
and the system changes.
Move the pitch: see which system takes over and at which threshold anti-slip measures become mandatory.
Pitch
30%
Angle
17°
Required system
Anti-Slip type (P) FKD58 SD
Applied with shear barrier profiles and erosion fleece. This is the system’s design range.
- System
- Anti-Slip system type (P) FKD58 SD
- Design range
- 25% – 70% · max. 35°
- Substrate wet density
- max. 1300 kg/m³
- Planting
- Succulents, Sedum species
- Safety
- Full-body harness and lifeline mandatory
If a root gets through,
everything gets through.
The most common green roof failure comes from a single decision: using waterproofing without root resistance. The damage advances while the roof is still perfectly green.
- Vegetation
- Garden substrate
- Waterproofing — NO root resistance
- Structural slab
- ROOT BREACH
- Leak at the ceiling
- 01
The root finds the membrane
A root searches for water. In a membrane without root-resistance certification it finds the lap joint and the smallest weak point.
- 02
It penetrates
The root enters the membrane, thickens and splits the layer apart. Nothing is visible from the surface.
- 03
Water spreads underneath
Water enters through the puncture and travels between membrane and concrete. Where it gets in is no longer where it comes out.
- 04
It appears on the ceiling
Damp patches, efflorescence, blistering paint and stalactites on the car park or top-floor ceiling. Repair means stripping every layer.
The fix is one line
The waterproofing membrane must carry an EN 13948 root-resistance certificate. Where it does not, a btm GREEN Kök Tutucu 350 root barrier foil (4 m × 50 m) is laid over the waterproofing to provide it.
No green roof regulation.
It has standards.
No regulation, standard or code of practice for green roofs has been published in Turkey. Work is carried out against the German FLL guideline and product-level TSE standards.
A green roof also earns credits under YeS-TR, Turkey’s National Green Certificate System. If you are planning for certification, the roof build-up should be chosen accordingly from the outset.
Test plant Pyracantha coccinea, test container 1300 × 800 × 250 mm. BTM Elastobit PE 4 Botanic was tested to this standard by Hochschule Weihenstephan-Triesdorf.
Guidelines for the Planning, Construction and Maintenance of Green Roofing. The reference the sector works to, as Turkey has no equivalent.
Under its application rules, pipe and outlet diameters may not be less than Ø100 mm. The outlet skirt must be mesh or textile.
Three build-ups,
three separate sheets.
Whether the roof is insulated, whether the waterproofing is bituminous or liquid-applied, and what sits below all change the layer order. The build-ups below are taken from BTM Optigreen system detail sheets.
Garden roof with bituminous membrane
10 layers · ölçeksizdir / do not scale- 01Vegetation
- 02Garden substrate
- 03BTM Green system filter · SF 32, 110 gsm
- 04BTM Optigreen FKD 25 drainage board · H: 25 mm, water-retention cells
- 05BTM Green moisture-retention mat · 500 gsm
- 06BTM Botanik Elastobit PE4 · polyester fleece reinforced, EN 13948
- 07BTM Elastobit PE3 · polyester fleece reinforced
- 08BTM Bitümer primer
- 09Screed to falls · min. 2%
- 10Structural slab
Inverted insulated garden roof
10 layers · ölçeksizdir / do not scale- 01Vegetation · grass or sedum based
- 02Garden substrate · lightweight engineered mix
- 03BTM Green system filter · 110 gsm
- 04BTM Optigreen FKD 25 drainage board
- 05BTM Green high vapour-permeability separation layer · 90 gsm
- 06BTM Polpan thermal insulation · extruded polystyrene
- 07BTM Botanik PE4 waterproofing membrane · EN 13948 / FLL certified
- 08BTM elastomeric waterproofing membrane PE3
- 09Screed to falls
- 10Levelling layer · structural slab
Green terrace roof with liquid membrane
8 layers · ölçeksizdir / do not scale- 01Vegetation · extensive planting
- 02BTM Optigreen system filter · 110 gsm
- 03BTM Optigreen FKD 25 drainage board
- 04BTM Green moisture-retention mat · 500 gsm
- 05BTM Green root barrier
- 06BTM Seal next-generation liquid waterproofing + primer
- 07Screed to falls
- 08Structural slab
Edge detail: gravel strip · grating · leaf trap · vertical outlet. Under TS 11758-2, pipe and outlet diameters may not be less than Ø100 mm.
The idea of a garden on a roof
is 2,700 years old.
Let’s draw your roof section together.
Tell us your pitch, structural load and planting preference and we will say which build-up fits, then prepare the detail sheet for your project.
We’re ready for
your next project.
Contact us for a free survey, technical consultancy and a fast quote.