If you are building a road base on soft ground, stabilizing a commercial parking lot with continuous vehicular traffic, or reinforcing the subgrade of an industrial platform, biaxial geogrid is the component that separates a work that lasts for decades from a project that shows deformation in a few months. This MOLTEXO PP biaxial geogrid delivers 40 kN/m of bidirectional strength in a 6 m × 50 m roll, a dimension calibrated for seamless extension in most road and platform construction. This guide explains the correct procedure for laying, overlapping, fixing, and filling so that the geogrid provides the bearing capacity calculated in the project.
The installation procedure is simple but strict: insufficient overlap at joints, incorrect roll orientation, or inadequate aggregate compaction can nullify up to half of the designed structural capacity. Read it entirely before starting the laying process: the difference between a successful project and one that shows potholes in the first year is almost always in the installation technique, not in the quality of the geogrid.
Product Specifications
The biaxial polypropylene geogrid is offered in a single standard presentation of 6 m wide by 50 m long, with an auditable bidirectional strength of 40 kN/m. The following table shows the full technical specifications of the only available variant:
| Specification | Value |
|---|---|
| SKU | 561774 |
| Material | Extruded virgin polypropylene (PP) |
| Orientation type | Biaxial (stretched in two directions) |
| Tensile strength | 40 kN/m (2.74 kip/ft) in both directions |
| Opening shape | Rigid square/rectangular |
| Roll width | 6 m (19.7 ft) |
| Roll length | 50 m (164 ft) |
| Area per roll | 300 m² (3229 ft²) |
| Chemical resistance | Inert to acids, alkalis, and soil microorganisms |
| Estimated service life | Decades in buried conditions |
| Primary application | Horizontal reinforcement of bases and subgrades |
| Color | Black (with anti-UV carbon black additive) |
The sister guides for PP uniaxial geogrid and PP triaxial geogrid cover the other two orientations in the family: uniaxial is specifically designed for MSE walls and slopes (directional loads with low creep), and triaxial delivers optimized omnidirectional confinement for very soft subgrades or complex vehicular traffic.
Step-by-step installation guide
The following procedure covers the complete on-site installation cycle: from subgrade preparation to aggregate compaction over the geogrid. Supervision by a qualified geotechnical engineer or site resident is always recommended for structural projects; the following guidelines are indicative and do not replace the specific engineering design for each project.
Subgrade preparation
Clear the surface of roots, large stones, and vegetation. The subgrade must be level (no potholes greater than 5 cm) and compacted to the minimum density specified in the project. Avoid laying the geogrid on water-saturated soil: if the subgrade shows surface water after rain, drain or wait for it to partially dry. A geogrid laid on mud does not provide reinforcement because the aggregate matrix cannot be properly confined.
Roll laying
Unroll the geogrid lengthwise along the work (road axis, platform axis). The direction is relatively flexible because the biaxial geogrid works in two directions, but it is advisable to maintain visual consistency throughout the project. Keep the geogrid taut during laying—folds and wrinkles reduce the aggregate's confinement effect. If multiple rolls are needed, align them so that the joints are perpendicular to the main expected direction of traffic.
Overlapping at joints
When joining two rolls, overlap a minimum of 30 cm at longitudinal joints and 50 cm at transverse joints (i.e., in the main direction of traffic). For very soft subgrades (CBR less than 3), increase the transverse overlap to 1 meter. The rule of thumb: if the subgrade sinks when stepped on, the overlap should be greater. Never cut the geogrid to "make use" of a scrap at joints; always do it with continuous overlap.
Temporary anchoring with pins
Use metal rods or J-shaped fixation pins every 1-2 meters to keep the geogrid in position during the filling operation. The fixation is temporary—its only purpose is to prevent the geogrid from moving when machinery passes with the aggregate. For large extensions in windy conditions, add sandbags or large stones along the edges.
A field trick to verify proper overlap: have a worker walk over the joint before filling, without compaction, and observe if the geogrid lifts or shifts. If it moves more than 2-3 cm, increase the overlap or add more anchors. Performing this check with personnel before running machinery reveals laying problems that are irreparable after compaction.
Filling and compaction
Dump the aggregate over the geogrid WITHOUT DRIVING machinery directly over the exposed geogrid. Maintain at least 15 cm of aggregate between the tracks or wheels and the geogrid. Distribute the aggregate in layers of a maximum of 30 cm and compact each layer to the Proctor percentage specified in the project before laying the next. Compaction is where the mechanical confinement provided by the geogrid is "activated"—poorly compacted aggregate does not interlock with the geogrid, and the investment is nullified.
Do not use biaxial geogrid where the project requires uniaxial (MSE walls, slopes of considerable height, abutments). Biaxial has moderate bidirectional strength and low creep resistance under sustained load. In an MSE wall several meters high, a 40 kN/m biaxial instead of an 80 kN/m uniaxial can progressively deform over years until collapse. The selection between biaxial, uniaxial, and triaxial is NOT optional or interchangeable: it depends on the direction and type of load calculated by the structural engineer.
Is biaxial 40 kN/m enough for your project?
The choice between biaxial 40 kN/m and higher strength options, or switching to triaxial, depends on project variables: subgrade bearing capacity (CBR or resilient modulus), available fill thickness, expected traffic type, and project life. Ask the virtual assistant with your site's geotechnical report (or soil conditions) and traffic type, and we will guide you to the correct selection without over- or under-sizing.
Complementary products
To complement the biaxial geogrid in road base and subgrade reinforcement projects, the following products cover the most common adjacent needs during design and installation:
The PP triaxial geogrid is the highest performing alternative for very soft subgrades or heavy vehicular traffic: the triangular geometry confines the aggregate in three directions and allows for an even greater reduction in fill thickness compared to the classic biaxial geogrid. The PP non-woven geotextile is installed as a separation layer under the biaxial geogrid when the subgrade consists of fine particles (silts, clays) that can contaminate the aggregate due to fine pumping during operation. Metal rods are used for temporary anchoring of the geogrid during spreading and before the first fill. The PP uniaxial geogrid is the specific solution when the project includes MSE walls or slopes that require high directional strength and low creep.
Maintenance and care
Geogrids do not require maintenance during their service life because they are designed to remain buried under an aggregate layer and pavement. The relevant care involves storage and handling prior to installation: rolls should be stored horizontally, covered to protect from direct sunlight (although PP contains an anti-UV additive, prolonged sun exposure degrades surface properties), and on a clean surface that will not puncture the original packaging.
During on-site handling, avoid dragging rolls over stones or metal with sharp edges that could tear the roll before spreading. A 30 cm transverse cut in a full roll significantly reduces the useful area of the product, due to the affected zone and adjacent material that also provides no reinforcement. Visually inspect each roll before spreading, especially the edges that may have been damaged during transport.
Frequently Asked Questions (FAQ)
What minimum overlap should I use at joints?
For subgrades in good condition (CBR greater than 5), 30 cm for longitudinal joints and 50 cm for transverse joints are sufficient. For soft subgrades (CBR between 1 and 3), increase transverse joints to 75 cm or 1 meter. For very soft or marshy subgrades (CBR less than 1), consider using a stronger geogrid or adding a separation geotextile under the mesh. Joints with insufficient overlap are the main cause of localized potholes in pavements with apparent geogrid.
Can I use biaxial geogrid on water-saturated soil?
Technically yes, but performance will be limited: the aggregate cannot be properly confined on saturated mud, and the effect of the mesh is greatly reduced. If the project requires extending geogrid over saturated soil, add a layer of non-woven geotextile under the mesh for separation and filtration, and consider an additional layer of coarse drainage aggregate. The ideal solution is still to drain the soil before installation.
How many m² does one roll cover and how many rolls do I need for my project?
A 6 × 50 m roll covers a nominal 300 m². To calculate the actual number of rolls, add the overlap: in standard work, an efficiency of 85-90% is realistic (10-15% is "lost" in overlaps and cuts at edges). For a 1000 m² platform, estimate between 3.7 and 4 rolls. If the project has irregular shapes or frequent changes in direction, reserve an additional 5-10% for on-site adjustments.