The hardscape industry is incorporating new products to help support the beautiful products that are used to create driveways, walkways, patios, and outdoor living spaces to ensure that they last as long as they possibly could. These products can help to accomplish the stabilization, separation, filtration, and drainage when used in the base material of paver projects and retaining walls.
Two materials that we use through the preparation of our base material for paver and retaining wall projects besides the aggregate itself can be categorized as Geotextiles and Geogrids. These both have overlapping applications and uses, but are two distinctively different products. In this article we will discuss the differences between the two and what their applications and uses are in the hardscape industry.
Geotextile vs Geogrid
Geotextiles are different from Geogrids, but both have overlapping purposes in the construction process. As derived from the name “Geo” they both have purposes with earth, but one is a fabric while the other is a grid. These are both used in hardscapes in the base material or pavers and the base and backfill material of retaining walls. There are also a variety of products within each of these that we will explore as well as their attributes and applications within the construction of paver and retaining wall projects.
Geotextiles can be categorized as woven, non-woven, and heat-bonded. Breaking down the word geotextile will tell you that these are earth fabrics (“Geo” meaning earth and “Textile” meaning fabric) meant to be installed to separate, reinforce, filter, and drain. Though within the category of geotextiles are variances that will provide a variety of different uses and applications. Some do better with filtration and drainage will others do better with reinforcement. They all provide separation which is important to ensure that the compacted subsoil does not contaminate the aggregate base material.
Learn more about the differences between non-woven and woven geotextile.
The two main types used in the construction of pavers and retaining walls are woven and non-woven geotextiles:
These fabrics are made of polypropylene filaments that are connected to a network. This fabric will have a feel that is more plastic than non-woven and is used where reinforcement or stabilization is more crucial than drainage.
These fabrics are made of polypropylene fibers rather than filaments and are randomly connected through a network. This fabric will have a felt-like feel to it and will be used in applications where drainage is more crucial than reinforcement. In situations where both drainage and reinforcement are crucial, a biaxial geogrid can be placed immediately on top of non-woven geotextile which will provide the necessary stabilization or reinforcement of the material placed on top.
Geotextiles are primarily used for separation of the subsoil from the base material. This ensures that over time the subsoil is not contaminating the base material from the transfer of force that the pavement will experience from the traffic. Woven geotextiles will provide added reinforcement or stabilization of the material placed on top, but provide less or very poor drainage. Non-woven geotextiles will provide less or poor reinforcement or stabilization of the material placed on top, but provide excellent drainage and filtration characteristics.
These materials are placed at the bottom of the excavated area in both retaining walls and paver projects after the subsoil has been compacted. They are meant to be in tension prior to the base material being installed on top and to wrap up the sides of the excavated are as well. The tension ensures that if there is any settlement or heaving, the fabric will stabilize the area above or below it. Wrapping up the sides of the excavated area ensures there is no contamination between the subsoil on the sides to the base material.
Is Geotextile Necessary?
In modern hardscape projects with both retaining walls and pavers, geotextile is a necessary material to install to help with stabilization, drainage, filtration, and separation. It is an inexpensive product for what it is able to accomplish and to help your business stand above others in the industry that may not have yet caught on. Use this as an additional selling point to your client to help them understand how you go above and beyond so they can see how you compare to others if they may be seeking competing bids on a project.
Geogrid is a grid-like material that helps to stabilize aggregates placed on top of it. It can be used in combination with geotextile in the installation of paver projects and in the backfill area of retaining walls. Unlike geotextile which typically has four different benefits including stabilization, separation, drainage, and filtration, geogrids focus solely on separation though because of their design drain well also.
How Geogrid Works
Geogrid works to stabilize material placed on top of it. This is accomplished by the aggregates placed on top striking through the apertures or holes in the geogrid which create lock up. This stabilization helps prevent settling or heaving and can be used in the base material of pavers or the backfilled area of a retaining wall.
Geogrid Types and Applications
There are three prominent types of geogrids including uniaxial, biaxial and triaxial.
Uniaxial geogrid has rectangular shaped apertures or holes in the grid and have strength in a singular direction. They are used primarily in retaining walls and need to be rolled out perpendicular or in the direction of strength designated on the roll of grid. This starts at the face of the retaining wall and extends typically at least 3 feet into the drainage and backfilled area of the retaining wall. It is never overlapped and requires at least 4 inches of aggregate material placed on top of it from one layer to the next. The placement heights in the wall and extension into the retained area is designated by engineered drawings by retaining wall block manufacturers or by engineers if the wall surpasses these drawings in height or based on the retained area, slope, and surcharge placed on the wall. It should also be installed in tension much like geotextiles.
Biaxial geogrid has strength in two directions and is typically more rigid than uniaxial and has square shaped apertures or holes in the grid. This is primarily used in paver projects. Biaxial geogrid does require an overlap of at least 12 inches and the lower it is placed in the base material the better. It is recommended to also have at least 4 inches of material placed on top of it if you plan to install more than one layer of it in the base material. It should also be in tension when installed similar to that of geotextile but does not need to wrap up the sides of the excavated area.
Triaxial geogrid has the same characteristics and applications as biaxial but has strength in three directions with triangular apertures or holes in the grid.
Is Geogrid Necessary?
In the construction of modern hardscape projects, it has absolutely become a necessity beyond retaining walls. It is also an inexpensive product and much like geotextile can help set yourself apart from competitive bids on a project if you can explain to your client the benefits of using geogrid in their paver project which has not completely caught on in many areas still.