Integrated Drainage Systems: The Synergy of Membrane and Pipe

Solutions & Applications · Drainage

In basement walls, retaining walls, green roofs and planters, ‘half’ drainage is often worse than none at all. A membrane without a pipe collects water at the base of the wall; a pipe without a membrane leaves the pressure acting on the waterproofing; a drainage layer without an outlet on a flat roof simply stores water above the waterproofing. The system only works when the drainage layer and the outlet are designed together.

Four elements, one system

Item	Role	What happens if it is missing?
Drainage layer	It directs water towards the collection point and protects the waterproofing from backfill or the sub-base	Water rising up the wall or standing water on the flat roof — pressure on the waterproofing
Filter	Keeps fine particles from the soil or substrate out of the channel	The channel gradually fills with silt and ceases to drain
Perforated pipe or spout	It receives the flow and diverts it away from the site	Water collects at the foot of the foundation or in the corner of the planter
Gravel enclosure & geotextile	Allows water to enter the pipe quickly without blocking the holes	The holes become blocked and the pipe stops collecting

The drainage layer: with or without a filter

Product	Structure	When to choose
DRAIN E 400	HDPE, 5 mm cones, without filter	Clean, coarse-grained fill and limited available thickness
DANODREN H15 PLUS	7.5 mm HDPE with pre-bonded geotextile (O90 60 μm) · compressive strength 180 kN/m²	Walls with backfill containing fine-grained material — the typical case for excavated material
MAXISTUD GEO	20 mm HDPE with geotextile · compression 150 kPa	Greater flow rate, high walls, green roofs in a single installation
MAXISTUD F	20 mm HDPE without geotextile · compressive strength >150 kN/m² · water retention and drainage of excess water	Green roofs, always with a separate filter geotextile on top
QDRAIN C20 65 10F	20 mm PP monofilament core sandwiched between two filter geotextiles	High loads and deformations; filters on both sides, regardless of the direction of installation
Nophadrain ND 4+1h	17 mm HIPS core with geotextile filter; compression 600 kPa; water retention 4.3 l/m²	Extensive and intensive green roofs with increased drainage depth and a need for water storage

The criterion is not the depth but the particle size distribution of the material underlying the layer. When the trench is backfilled with excavated material or when there is a planting substrate on top, fine particles are present — and without a filter, they will end up first in the channel and then in the pipe.

The provision at this level is to be read in conjunction with the method

The data sheets provide flow rates in-plane, but not in the same way: DANODREN H15 PLUS specifies 0.54 l/m·s in accordance with EN ISO 12958, MAXISTUD GEO 10.00 l/m·s at 20 kPa according to EN ISO 12958-1, and QDRAIN C20 65 10F 3.7 l/m·s at 20 kPa according to ASTM D4716. A different standard, load or hydraulic gradient means that the figures cannot be directly compared. In the design, we require values at the same load as that which the layer will bear — backfill, planting substrate or traffic.

Drainage: GEODRAIN or GEODRAIN PLUS

Pipe	Structure	When to choose
GEODRAIN	Double-walled HDPE — smooth on the inside, corrugated on the outside; SN4; 360° perforation, >50 cm²/m; Φ63–Φ200	Casing with clean gravel and a separate geotextile for filtration
GEODRAIN PLUS	The same pipe with a factory-fitted sleeve of non-woven geotextile, 150 g/m²	Soils containing sand or silt, and where the separate wrapping is at risk of being omitted or displaced in the backfill

The pipe is laid with a continuous gradient towards the collection point, with inspection chambers at the corners and a clear outlet — an absorption chamber, a stormwater network or a natural receiving body. A network that is not inspected is not maintained, and a blocked perimeter pipe gives no indication of a problem until damp appears in the basement.

Green roof and planter: the same principle, applied horizontally

In a planted slab, the ‘pipe’ refers to the drainage outlet or the gutter. The drainage layer covers the entire surface and must extend to the drainage point without interruption — otherwise it acts as a reservoir above the waterproofing.

Layering — from top to bottom	Role	Key point
Planting substrate	Plant growth	It does not come into contact with the drainage cavity
Filtration geotextile	Retains the fine particles of the substrate	In MAXISTUD GEO, it is integrated and faces upwards; fitting it the wrong way round disables the filter
Drainage layer	Water storage for plants and drainage of excess water	Continuous up to the opening; selection based on the load of the substrate
Root barrier protection	Prevents roots from reaching the waterproofing	The drainage layer is not root-resistant; ESHAPROTECT becomes root-resistant only when the seams are heat-sealed.
Waterproofing	Waterproof barrier for the slab	It rises to the parapets above the final level of the sub-base

The same principle applies to planters on a smaller scale: any corner without a drain is a point where water collects. In long perimeter planters, a perforated pipe at the base directs the flow to the drainage holes, just as at the base of a wall.

Mistakes that cost

Incorrect	Consistency
The membrane stops above the pipe	Water pools in the joint between the plinth and the wall
Filterless layer on backfill or sub-base with fine-grained material	Silent blockage of the channel within a few years — rectification involves excavation or dismantling of the garden
Filter fitted the wrong way round	The product behaves like a plain membrane without a filter
Pipe without a continuous slope or without an outlet	Water simply flows to the lowest point in the system
No inspection chambers	No means of inspection or cleaning — the problem only becomes apparent when damp emerges

The sequence of works on the wall

1. Complete, dry wall waterproofing and acceptance before anything else.
2. A geotextile filter at the base and on the slopes of the trench at the base, with excess material for tucking in.
3. A layer of gravel and a perforated pipe sloping towards the collection point.
4. A drainage layer on the wall — tapering towards the wall, with a filter facing the ground — which extends down into the pipe’s casing.
5. Cover the pipe with gravel and fold the geotextile over the top.
6. Inspection chambers at the corners and connection to the receiving tank.
7. Backfilling in layers, ensuring that no large stones come into contact with the membrane.

Drainage Layers

Drainage, Filters & Protection

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