You have just purchased drainage geocomposite to solve drainage behind a retaining wall, in a buried basement, or on a green roof. The product replaces bulky layers of drainage gravel with a thin solution that captures ground water and channels it to the drainage system. In this guide, we explain how to install it correctly and, crucially, how to orient it so that it works: the correct side against the wall is decisive.
Product Specifications
The drainage geocomposite is a sandwich-like structure: two non-woven geotextiles that filter water and allow only liquid without particles to pass through, plus a three-dimensional geonet core in the center that channels this water to the evacuation point. The geotextiles act as a filter and the geonet’s voids act as a flow channel. The Dodom range is offered in a standard configuration for retaining walls, buried basements, and green roofs.
| Specification | Drainage Geocomposite |
|---|---|
| SKU | 746941 |
| Composition | Non-woven geotextile + Geonet + Non-woven geotextile |
| Function | Filtering and in-plane drainage |
| Roll width | 5.8 m (19 ft) |
| Roll length | 100 m (328 ft) |
| Coverage per roll | 580 m² (6243 ft²) |
Step-by-step installation guide
The geocomposite replaces the traditional drainage gravel layer but requires correct installation to function. The geotextiles must be in contact with the moist soil to capture water, and the geonet in the center channels this flow to the base of the wall. Any inversion of the order renders it useless.
Prepare the wall face
Apply asphalt waterproofing or a membrane to the buried face of the wall and let it dry. The wall's waterproofing and the geocomposite work together: the former prevents water from entering, the latter channels water that arrives before it creates hydrostatic pressure.
Install drainage pipe at the base
Place perforated pipe at the base of the wall, on a gravel bed, with a minimum slope of 1% towards an evacuation point. The geocomposite channels water to this pipe. Without the pipe at the base, water accumulates, and hydrostatic pressure returns.
Unroll the geocomposite against the wall
Unroll the material vertically, from the top of the wall downwards. Support the geocomposite against the waterproofed face of the wall. The lower edge must rest on the gravel of the drainage pipe so that descending water flows directly into it.
Secure the top edge to the wall
Use impact nails with a wide washer or asphalt-compatible contact adhesive to secure the top edge every 50 cm (20 in). The fastening is only temporary; its function is to hold the geocomposite in position until the backfill presses it against the wall.
Overlap adjacent rolls
Overlap vertical adjacent rolls by 20 cm (8 in). At the overlap, ensure that the geonet of the new roll interlocks with that of the previous one; the geotextiles cover the joint and prevent soil from entering the drainage net.
Gradually backfill the wall face
Pour backfill soil behind the geocomposite in 30 cm (12 in) layers and compact each layer with a light compactor. The backfill load is what presses the geocomposite against the wall and ensures full contact. Compact gently to avoid tearing the outer geotextile.
Seal the top edge
At the top of the wall, seal the upper edge of the geocomposite with waterproof sealant or an overlapping membrane. The goal is for surface water to enter through the backfill soil (filtered by the outer geotextile) and not over the geocomposite itself.
The geocomposite replaces at least 50 cm (20 in) of traditional drainage gravel while occupying only a few millimeters. In urban basements where every centimeter of excavation costs money, that recovered space translates into more usable square meters within the basement. Calculate this before budgeting for the project.
Do not install the geocomposite without a drainage pipe at the base of the wall. Without that outlet, the water captured by the geocomposite accumulates at the base, the lower geotextile becomes saturated, and the entire system stops draining. Hydrostatic pressure returns, and the wall ends up with moisture. The pipe at the base is not optional.
Geocomposite or dimpled drainage sheet?
If you are unsure between drainage geocomposite and dimpled drainage sheet for your wall, or don't know how to size the drainage system at the base, ask the virtual assistant. It will guide you based on wall height, soil type, and expected water table level.
Complementary products
For a professional installation of the geocomposite in a retaining wall, the following complementary products cover critical functions that the geocomposite alone does not solve.
The dimpled drainage sheet is the ideal alternative for low walls (less than 2 m high) or planters where the expected water flow is low: simpler and more economical than geocomposite. The metal rod is used to temporarily fix the upper edge when it is not feasible to nail to the waterproofed wall, anchoring against the backfill soil. The anchor cap distributes the pressure and prevents puncturing the geotextile.
Maintenance and care
The geocomposite is a buried system designed to function for decades without intervention. Care focuses on protecting the drainage system at the base of the wall:
- Annual inspection of the evacuation point: check the pipe outlet at the base. If it is obstructed by sediment or vegetation, clean it. A blocked outlet saturates the entire system from the bottom up.
- Attention to damp stains on the wall: if permanent dampness appears on the interior face after the first rainy season, it usually means that the drainage system is not evacuating. First check the pipe at the base before considering waterproofing.
- No subsequent punching: any subsequent work that excavates next to the wall can damage the geocomposite. Mark the area on plans so that future work respects its location.
- Storage of leftover roll: protected from direct sunlight. Geotextiles have UV treatment, but prolonged exposure before installation reduces the useful life of the entire system.
Frequently asked questions
What is the difference between drainage geocomposite and dimpled drainage sheet?
The dimpled sheet is a plastic plate with raised patterns that creates an air chamber between the wall and the soil: cheap and effective for low walls. The geocomposite incorporates geotextiles on both sides of the drainage core, so in addition to evacuating water, it filters fine particles from the soil and works with higher flows. For walls over 2 m high or soils with many fine particles, use geocomposite. For low walls in gardens, use dimpled sheet.
Do I always need a drainage pipe at the base of the wall?
Yes, without exception. The geocomposite is only the water conductor: the pipe is what removes it from the area. If there is no pipe at the base, water accumulates at the bottom and saturates the entire system. The practical rule is: before buying geocomposite, make sure the outlet at the base is resolved.
How high of a wall does this geocomposite work for?
Dodom geocomposite is dimensioned for buried walls up to 8 m high under standard soil conditions. Above this value, the accumulated flow requires a drainage core with greater capacity or systems with intermediate piping (staircase drainage). For very high walls or with a high water table, consult the virtual assistant for specific dimensioning.