Geotextile in Waterproofing Systems: Why and Where to Use It
Date Published
When it comes to waterproofing, people usually think of roll materials, mastics, and membranes. Geotextile often remains in the background — it is considered an auxiliary material that can be economized on. This is a mistake. Without properly selected geotextile, even the most expensive membrane can fail within just a few seasons.
In this article, we will explain what geotextile is, what functions it performs as part of waterproofing systems, how to choose the right density, and where its use is truly necessary.
What Is Geotextile?
Geotextile is a roll-form synthetic material made from polypropylene or polyester fibers. It looks like a dense nonwoven fabric or felt. The material is permeable to water and resistant to rot, soil acids and alkalis. It does not decompose in soil for decades.
The key point to understand is that geotextile itself is water-permeable and is not a waterproofing material. Its purpose is not to retain water, but to protect, filter, separate, and reinforce. In a waterproofing system, it always works together with a waterproof material rather than replacing it.
Five Functions of Geotextile in a Waterproofing System
1. Protecting Waterproofing from Mechanical Damage
This is one of the most important functions. Membranes and roll waterproofing materials are vulnerable to punctures caused by sharp stones, gravel, construction debris, reinforcement bars, and plant roots. During foundation backfilling or installation of drainage gravel, a single sharp stone can puncture the membrane and compromise the entire system. The geotextile layer absorbs mechanical loads and distributes them across the surface.
2. Drainage and Water Removal
Geotextile allows water to pass through freely while retaining soil particles. This allows water to flow toward drainage pipes without clogging the system with silt. As a result, the structure remains dry and hydrostatic pressure on the waterproofing layer is reduced.
3. Filtration
The material acts as a filter: it allows water to pass through while retaining fine soil particles that could gradually clog the drainage system or gravel layer. This directly extends the service life of the entire drainage system.
4. Separation of Layers
Geotextile prevents different materials from mixing — for example, soil and drainage gravel or a sand cushion and clay substrate. Each layer retains its intended function and remains separated from adjacent layers under loads and over time.
5. Reinforcement of the Base
High-density geotextile redistributes loads and increases the bearing capacity of weak soils. This is especially important under roads, parking areas, loading areas, and access roads.
Types of Geotextile
Depending on the manufacturing method, geotextile is divided into three main types:
• Woven geotextile — manufactured by interweaving threads and characterized by high tensile strength. It is primarily used for reinforcement and strengthening of foundations.
• Nonwoven needle-punched geotextile — fibers are mechanically bonded using numerous needles. It provides excellent filtration and drainage while maintaining water permeability. This is the most common type used in waterproofing systems.
• Nonwoven thermally bonded geotextile — fibers are bonded together under the influence of heat. It is denser and stronger, provides good resistance to mechanical loads, but has slightly lower filtration performance.
The key characteristic when choosing geotextile is density, measured in grams per square meter (g/m²). The higher the density, the stronger the material and the greater the loads it can withstand.
How to Choose Geotextile Density
The density of geotextile should be selected according to its purpose and the expected load. Recommended approximate values:
• Drainage systems, filtration — 150–200 g/m²
• Separation layer (sand/soil) — 200–250 g/m²
• Foundation membrane protection — 300–400 g/m²
• Green roofs — 250–350 g/m²
• Roads, parking areas, platforms — 350–500 g/m²
• Reinforcement of weak soils — 400–600 g/m²
General rule: if you are choosing between two density values, select the higher-density material. The difference in price is insignificant compared with the cost of repairing damaged waterproofing.
Where Is Geotextile Used?
• Foundation waterproofing — as a protective layer over the membrane before backfilling with soil or gravel.
• Drainage systems — around buildings, basements, and retaining walls.
• Intensive and green roofs — to protect the membrane and separate the layers of the roof system.
• Swimming pools and artificial ponds — to protect PVC film or membranes from root penetration and mechanical damage.
• Road construction, parking areas, and platforms — for reinforcement and separation of base layers.
• Terracing and retaining walls — for soil stabilization and water drainage.
Common Mistakes When Using Geotextile
• Completely avoiding geotextile to save money. One of the most expensive mistakes: repairing a damaged membrane can cost many times more than a roll of geotextile.
• Using insufficient density for heavy loads. Thin material under gravel or construction equipment can tear and lose its protective function.
• Insufficient overlap between sheets. Sheets should overlap by at least 15–20 cm. Otherwise, soil can penetrate through the joints and reach the waterproofing layer.
• Using geotextile instead of waterproofing. Geotextile is water-permeable — it does not retain water and cannot replace a membrane or mastic.
A Consultation with a MARJA Specialist — Free of Charge
If you are not sure which material suits your project, give us a call. MARJA specialists will select the optimal solution, taking into account the type of structure, the climatic conditions of your region, and your budget.
Phone: +998 77 057 57 53
E-mail: info@marja.uz
MARJA — a manufacturer of waterproofing materials in Uzbekistan since 2004.
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