Geosynthetics Part 1: Geotextiles

Geosynthetics can be grouped into several product categories; geotextiles, geogrids, geomembranes, geonets, geosynthetic clay liners, geopipes, geofoam, geocells and geocomposites. This article examines construction with geotextiles and future articles will cover construction using the other geosynthetics. The articles are excerpted from a soon-to-be released ICPI Tech Spec that provides a comprehensive view of geosynthetic materials, selection, and construction in various segmental concrete pavement assemblies.


When placing geotextile avoid wrinkles in the fabric. Follow the overlap recommendations specified in AASHTO M-288 Geotextiles for Highway Applications as noted in Table 1. Make sure the geotextile is placed in full contact with the surrounding soils or aggregates. Voids, hollows or cavities from wrinkles created under or beside the geotextile compromises its intended function.

Figure 1 illustrates a familiar detail, i.e., separating the compacted aggregate base from the soil subgrade with geotextile. This can help maintain consolidation of the base materials over time by preventing intrusion of fines in the bottom and sides. This slows the rate of rutting in the base and on the soil subgrade.

Geotextile placed under the bedding sand next to the curb provides a ‘flashing’ function. This separates the sand from the base and prevents sand loss into joints between the concrete curb and the compacted aggregate base, as they are two structures that can move independently from each other. Table 2 provides guidelines for geotextile selection depending on the soil and fabric functions required.

Figure 2 illustrates geotextile on a concrete base in a crosswalk application. For new sidewalks, crosswalks and streets, 12 in. (300 mm) wide strips of geotextile are recommended over all joints in new concrete bases to prevent loss of bedding sand, as well as over weep holes. New asphalt generally should not require geotextile on it except at curbs, structures and pavement junctions where bedding sand might enter. For existing asphalt and concrete bases, the surface of each should be inspected for cracks, the severity and extent of which determines repairs. If cracks are few and minor (suggesting substantial remaining life in these bases), geotextile should be placed over the cracks to prevent potential future loss of bedding sand. Covering the entire asphalt or concrete surface with a loose-laid sheet of geotextile can present some risk of creating a slip plane for the bedding sand and paving units as a result of repeated vehicular traffic.


Figure 3 illustrates a typical application of geotextile in PICP. Its application against the sides of the subbase and against the excavated soil is essential in all PICP projects that do not use full-depth concrete curbs to completely confine open-graded aggregates at the pavement perimeter. The design and selection of geotextiles for PICP is covered in detail in the ICPI manual, Permeable Interlocking Concrete Pavements – Design, Specification, Construction, and Maintenance.


Playing with Fire

Playing with Fire

HNA 2013 attendees Jamel Taylor (left) and Wes Maggard discuss fireplace installation after the “Construction of Fire Features for Outdoor Living Areas” demo on Oct. 24.

However precisely contractors construct outdoor fire features like fire pits and barbecues using interlocking concrete pavers, experts say that sturdiness and longevity will be compromised unless the top soil and sod are thoroughly excavated.

“Ignore [base preparation] and everything done after that is a waste of time,” says Ross Yantzi, owner of Pavestone Plus Limited in Tavistock, Ontario.

Yet that part of the job often is neglected or shortchanged, especially among first-time landscapers. The base work is probably the most difficult, but most important phase of construction, Yantzi says. “That’s where people cut corners, by just building on top of soil. They’re saving money at the beginning, but keep spending more because [the structure] moves and eventually has to be repaired. We’ve done quite a few repairs, and whether it’s retaining walls or pavers, the reason behind most repairs is inadequate base preparation.”

View a gallery of photos from this year’s HNA demo: “Construction of Fire Features for Outdoor Living Areas.”

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Not one who takes chances, Jason Goodnight, Vice President of The Brick Doctor, Inc., usually adds a concrete footer when constructing fire pits and fireplaces for an even firmer foundation. The thickness of the footer depends on the application, he says. He recommends 4 in. (10 cm) for a standard fire pit under 3 ft. (1 m) tall and 6 in. (15 cm) for larger ones.

Placement of the fire feature is another key consideration. Some regulations require the fireplace or fire pit on a non-combustible surface that extends beyond its sides to a length equal to its height, according to Section 6 of ICPI’s Advanced Residential Paver Technician Manual. Several codes, including fire, plumbing and electrical, could apply to the construction of outdoor fireplaces, fire pits, grills and kitchens. Local bylaws, municipal ordinances and homeowner association covenants also may include regulations for outdoor living spaces, while some building departments require permits for the construction of outdoor kitchens and elements like outdoor fireplaces.

Another important requirement for the construction of fire pits and fireplaces is the use of specialized heat-resistant materials because of the extreme temperature differences these structures endure, the manual states. Fire pits sometimes are constructed without regard to heat dissipation. Concrete pavers and segmental retaining wall units aren’t made to withstand extreme heat. Fire-resistant, ceramic blocks should line the inside of fire pits.

To be more efficient and not burn money, measure and establish an average excavation time for one yard of soil, installation of one ton of base material, and build time for 10 sf (1 m2) of pavers. “You’re developing a database and making jobs more predictable,” says Yantzi. Professional landscapers and hardscapers also should be aware of things like access to back properties, where fire pits and barbecues typically are located, he advises. “Access impacts whether [a job] takes three days, five, 20 or 30.”

Another way to manage the bottom line is by establishing a realistic time budget for each design and a timeline for completing each project, Goodnight says. Otherwise, expenses can spiral rapidly, especially when customers want expensive features like stainless steel inserts and granite tops, he adds.

According to the 2013 Residential Landscape Architecture Trends Survey, across all categories, 97 percent of respondents rated fire pits and fireplaces as somewhat or very in-demand for 2013, followed by grills at 96.3 percent.

With concrete pavers available in a range of colors, shapes and sizes, these options enhance their popularity over other kinds of paving materials, says Goodnight.


The Numbers Tell the Story

There are just over 100 companies with 170 plants manufacturing concrete unit paving in the U.S. and Canada. Unit paving products (defined in Master Format Section 32 14 00) include interlocking concrete pavers and permeable interlocking concrete pavers that conform to ASTM C 936 Standard Specification for Solid Concrete Interlocking Paving Units or CSA A231.2 Precast Concrete Pavers, the U.S. and Canadian product standards. Unit paving also includes paving slabs and grid units. Interestingly, there has been a paving slab standard in Canada since 1972, CSA A231.1 Precast Concrete Paving Slabs, but no concrete grid product standard there.

Conversely, there is no ASTM paving slab standard for U.S. markets yet, but there is a grid standard, ASTM C1319 Standard Specification for Concrete Grid Paving Units. The reason there is no grid product standard in Canada is that the product isn’t specified much there. Regarding an ASTM standard for paving slabs, the good news is that an ASTM committee recently balloted a draft standard for commercial paving slab applications (typically pedestrian and roof plaza decks). The committee is working through revisions and re-balloting for possible approval later this year.

Like many construction product standards, most designers don’t memorize the requirements for ASTM and CSA paver and slab product standards. ICPI certifies that paving products have met applicable ASTM and CSA standards. ICPI producer members with current certifications can be found at

Each year, ICPI conducts a survey of unit paving manufacturers in the U.S. and Canada called the ”Industry Sales Profile.” The results from 2012 sales were recently received and provide some interesting numbers that suggest certain trends. The final report is for sale at

Here are some telling numbers: Paving slabs are seeing significant growth as well as pavers used in permeable applications to reduce stormwater runoff. The 2011 survey indicated just over 16 percent of all sales came from paving slabs. The 2012 survey indicates 34 percent. This speaks to a continuing trend toward larger units, especially in commercial and residential pedestrian applications.

Another interesting statistic is the increase in the portion of paving units for permeable pavement applications. These have consistently risen each year in spite of the recent Great Recession. The increase from 2011 to 2012 was 2.8 percent to 4.8 percent based on survey responses from the U.S and Canada. Since most permeable paving units conform to ASTM C936 or CSA A231.1, the portion of permeable paving units sold of all units conforming to these standards is around 8.3 percent in 2012, with 75 percent going to commercial and municipal uses. Grouping together pavers and slabs, this portion represents one-sixth to one-fifth of all the concrete paving units sold to commercial and municipal markets. The numbers are telling us a story about the growing acceptance of PICP.

In this issue, we explore the growth in permeable applications with intriguing case studies from Lancaster, PA, and Nashville, TN. The Nashville project replaced dysfunctional porous asphalt with concrete pavers, and Lancaster discovered substantial savings in the processing of combined sanitary and storm flows by developing a green infrastructure plan that includes permeable pavement. The proof is in the numbers: When selecting pavement for green infrastructure projects that provides the best performance, concrete unit paving is gaining recognition as the best choice.


Specialty Paver Applications

To make customers choose your business over others, you must offer unique services unavailable elsewhere. An easy, cost-effective way to do this is through specialty paver applications—small, customizable add-ons your company can offer to a customer in order to enhance the original design or capture more work in the project scope.

“It takes [your business] from ‘everybody does it’ to ‘only a few select people can do it,’” says Aaron Wolfe, vice president and CEO of Wickenburg Landscape in Arizona. “It sets you apart, makes your company the leader.”

What’s in stock

What exactly can you sell to a potential customer? One unique specialty application is down-lighting, Wolfe says, which is lighting installed into trees that casts shadows over the branches and leaves, creating a pattern on the pavers below. “It takes [the design] to another stratosphere,” Wolfe says.

Because the lights are installed and positioned during the day, when the expected shadow design isn’t visible, Wolfe says you must start the project knowing roughly what you’re going to do. “We don’t run the lights until the entire project is complete,” Wolfe says.

An added advantage of down-lighting is that it can be applied at any time, so the service can be marketed to people with existing installations as well as new. Plus, the extra lighting can even improve safety.

specialty2Custom paver designs are another specialty option to consider. Wickenburg Landscape recently installed a Cadillac logo measuring 10 ft (3 m) in diameter using pavers in a residential driveway. Wolfe says the company has also installed horseshoes, flowers, inlaid circles and mosaic patterns.

Make the sale

Added services mean extra costs to customers that they may not initially be willing to pay. To effectively market specialty applications, Wolfe says there is a good amount of customer research that needs to be done.

“You need to understand the history of your client as much as possible. A lot of people don’t get anywhere because they’re recommending the wrong thing to the wrong person,” Wolfe says. “Matching the customer with the specialty product is one of the big keys that contractors miss.”

This includes being realistic about budgeting — if the client clearly cannot afford an add-on, don’t try to sell one. However, if you think your customer may be willing to spring for extras but hasn’t mentioned them, consider upselling, says Bill Gardocki, president of Interstate Landscape Company, Inc., in New Hampshire.

“I include upsell items in every quote, even if the customer doesn’t ask for it,” Gardocki says. “Most people aren’t aware of what’s available, so you have to show them.” Gardocki’s secret is getting customers to the showroom, where they can actually see what a sitting wall or custom paver art looks like. After that, he says, 18 percent decide to purchase upsell items—despite having no initial interest in them. Another approach is presenting examples of lighting design, custom paver designs, or other unique options using high quality photos in your project portfolio and company website. The portfolio can be used to show design capabilities on sales calls and the website examples can be referenced anytime.

Be the expert

While the extra revenue gained from offering specialty applications is tempting, extra legwork is required to successfully sell them.

“It’s a landscaper’s responsibility to learn about the industry, the technology [and] the new advances and then take those ideas and find ways to incorporate them,” says Wolfe, who uses trade shows to get ideas from manufacturers or distributors and make contacts with creative people.

If you’ve done the proper research, you can have confidence in your product—and that attracts customers, Wolfe says. “If you have a passion to do this, it comes out. It makes it easy for me to sell this stuff because I talk to somebody and they can hear that I love everything I do.”

Wolfe’s enthusiasm and creativity sets the context for presenting design ideas to potential clients. As an existing condition to upselling projects, attitude and the ‘vibe’ you bring to future clients is probably the strongest selling tool, next to showing actual project examples. It’s easy to ask a client for business and then upsell when you energetically provide design ideas that delight them as well as provide useful features.


HNA 2013 Show Info

Hardscape North America is produced by the Interlocking Concrete Pavement Institute and endorsed by the National Concrete Masonry Association and the Brick Industry Association. HNA is collocated with GIE+EXPO, and together they are the 9th largest trade show in America.

Hardscape North America
October 23-25, 2013
Louisville, KY

Evening Concert Lineup

Three free concerts are planned — one each evening — at the Nissan Commercial stage at Fourth Street Live! Attendees won’t want to miss the after-show-hours fun.

Oct 23
7:30 p.m. – Jamie McLean Band
9:00 p.m. – Craig Morgan
Oct 24
7:30 p.m. – Angie Johnson
9:00 p.m. – Three Dog Night
Oct 25
8:00 p.m. – Olivia Henken
9:00 p.m. – Holly Williams

Outdoor Demonstration Area

The unique Outdoor Demonstration Area, just outside the indoor exhibits, covers 19 acres and showcases the newest equipment in the industry. The HNA Outdoor Arena gives attendees an exclusive, up-close-and-personal opportunity to learn the latest installation methods and techniques.


Return to the HNA 2013 Preview article


HNA 2013 Preview

Hardscape North America (HNA) is THE Hardscape show for contractors and distributors/dealers. It brings top-notch education, certification courses, products and technology to contractors and installers who build segmental pavements and retaining walls, and to distributors. With more than 750 exhibits indoors and out, networking opportunities, education and live demonstrations, HNA is the No. 1 trade show for the hardscape industry.

hna6New this year at HNA, top hardscape contractors from three countries will compete for the Hardscape North America Installer Championship. Competitors from Canada, the United States and Mexico will test their understanding of industry best practices, safety, quality and craftsmanship in a race against the clock and other top installers. This championship will determine the best of the best in the hardscape industry!

hna5HNA’s Distributor & Dealer Program, “What’s The Big Idea?” is set for Wednesday, Oct. 23, 9:30 a.m.–3 p.m., at the Kentucky Exposition Center. This optional full-day program is dedicated to distributors and dealers who sell hardscape and landscape products to contractors and consumers. The program will cover topics such as marketing, social media, sales strategies, retaining quality employees and more. Following the program, distributors and dealers are invited to an exclusive preview of the trade show and welcome reception. Also new this year, the Distributor & Dealer Program will start Tuesday evening with an optional networking reception where dealers and distributors will have the opportunity to come together for an evening of fun, networking and entertainment.

Back for a second year, the Hardscape Contractor Executive Workshop will focus on best practices for hardscape contractor owners and executives. Set for Wednesday, Oct. 23, 1:30–5:30 p.m., at the Hyatt Regency in downtown Louisville, this optional program will give seasoned hardscape contractors the opportunity to network with peers from across North America and share ideas on topics critical to their business.

The Interlocking Concrete Pavement Institute (ICPI) will host its Hardscape North America Conference Tuesday through Friday. Courses and sessions will take place at the Hyatt Regency (Tues-Wed) and at the Kentucky Exposition Center (Thur-Fri). Attendees can earn up to two years’ worth of continuing education credits for ICPI Certified Installers in one central location.

hna4HNA will announce the winners of the 6th Annual HNA Hardscape Project Awards at a breakfast banquet at the Hyatt Regency Louisville on Friday, Oct. 25th. The awards recognize the contractor’s quality construction and craftsmanship in outstanding commercial and residential hardscape projects in North America. Winners will be featured in Interlock Design magazine, other trade publications and on the HNA website.

A big hit last year, the $10,000 Friday Giveaway will start at 1 p.m. on Friday. Winners must be present to win $1,000 at 1 p.m., $2,000 at 2 p.m., $3,000 at 3 p.m. and $4,000 at 4 p.m. To be eligible, register for HNA. An entry form will be mailed along with badges and will include instructions for returning it on-site.

The New Products Showcase will be a launching pad for new products. Attendees can stop here for a glimpse of the latest innovations and make their must-see lists, then stop at the exhibits throughout the show floor to meet with the manufacturers and test the products.



Through a grant from the Interlocking Concrete Pavement Institute (ICPI), the University of Georgia’s College of Environment and Design (CED) has developed an innovative online learning resource called Paveshare. This website provides landscape architecture professionals, students and educators with a flexible, living, and robust resource for place making, environmental design and technical knowledge. This program was forged in response to a need in landscape architecture academia for increased design knowledge, creativity and technical competency with segmental concrete pavements.

The Paveshare website is developed on a foundation of multimedia and online learning educational theories. Its structure includes links to self-guided presentations with interactive animations and a growing studio project library that spans concept to construction. Faculty is encouraged to use the site to supplement existing curriculum and to encourage students to augment this living library by uploading their completed studio projects to the site. Students are encouraged to explore and interact with the site’s materials to become familiar with design and structural principles related to segmental concrete pavement, as well as industry technical resources.

Paveshare presents an open, graphic-driven, interactive, diverse and continuously changing online site that combines traditional and newer modes of learning that are sure to appeal to students of design. Familiar, self-directed learning formats such as presentations and quizzes are available to students, and are complemented by newer learning modes in landscape architecture, including interactive animations, tagged precedent libraries and an open contribution framework. Paveshare’s content team continuously cultivates site materials and acts as a vetting source for materials uploaded to the site, ensuring Paveshare is an adaptive environment. Users are also encouraged to post projects, photographs, and videos.

Browsing and contributing to Paveshare is intuitive and user-friendly. Users can browse by following learning paths or by using the library feature, which allows hunting for specific information by topic. All uploaded material is credited to the contributing author, so the desire to publish and share completed work, recognition for uploading compelling precedent project images, or class requirements will encourage students to contribute. The site also has links to and materials cultivated on several social media sites to foster cross-fertilization of knowledge sources and discussions.

The site functions as a comprehensive and constantly updating library of project precedents, design ideas and lessons, including specific interactive features that teach critical concepts specific to landscape architecture. Most importantly, these features have been made engaging and fun, especially when compared to the stuffy pages of Time Saver Standards familiar to most students. Paveshare complements studio methods and learning with features like design tools that help link abstract design and concrete materiality, which can be a difficult concept to teach while working on studio projects.

Through these capabilities, the wiki-based openness of the resource’s framework, and Paveshare’s social media portals, the developers hope that the site will ultimately reach a tipping point within student and faculty knowledge and social circles, and will become a self-sustaining, critical headwaters for integrating and expanding design inspiration and technical knowledge.

Related Links

Check out this video for an overview of the Paveshare website and how it works:


Get With the (New) Program

ICPI is pleased to announce the creation of the Accredited Paver Installation Company Program (APIC) to recognize companies that meet industry best practices.

In 1995, ICPI designed the ICPI Certified Installer Program, which has trained close to 20,000 individuals.A central concept of the ICPI Certified Installer Program is that an individual becomes a certified installer, not a company. As a result, some member companies have been unable to effectively promote that they follow industry best practices and ICPI guidelines. The new APIC program recognizes companies that consistently install interlocking concrete pavements in the U.S. and Canada to industry guidelines, best practices and according to professional principles.

Features of the program:

  • Marketing to promote APIC participants, including additional company listing and web links on the ICPI website;
  • A Construction Task List that requires trained personnel to be present at key construction steps;
  • A Code of Conduct that sets a model for businesses to follow.

Requirements for the program:

  • The owner/principal of the company must hold a current ICPI Certified Installer certificate;
  • An ICPI Certified Installer must be present on every job site and actively involved in each step identified in the Construction Task List that is part of the company’s scope of work;
  • The work performed by the company must be within their area of experience and of a scope similar to previous company projects;
  • All employees must comply with a company safety program;
  • The company must pledge to uphold the APIC Code of Conduct;
  • The company must maintain current commercial insurance policies and produce insurance coverage certificates when and where requested by ICPI or a customer.


Geomembranes in PICP

Permeable interlocking concrete pavement (PICP) systems can be designed and constructed to accommodate three drainage conditions:

  • Complete infiltration of water into to the high infiltration rate soil subgrade with no underdrains;
  • Partial infiltration of water into low infiltration rate soil subgrade with some outflow through underdrains;
  • No infiltration into the soil subgrade with all outflow exiting through underdrains.
  • All conditions have similar surfacing, and base/subbase reservoirconstruction. No exfiltration designs, however, use a geomembrane on the sides and bottom of the base/subbase reservoir to contain stormwater and prevent it from infiltrating into the soil subgrade. Commonly called an impermeable liner, Figure 1 illustrates a typical PICP design using such a membrane.

A no infiltration design with a geomembrane is typically used in the following conditions:

  • The soil has very low permeability, low strength, or is expansive;
  • High depth to a water table or bedrock;
  • To protect adjacent structures and foundations from water;
  • When pollutant loads are expected to exceed the capacity of the soil subgrade to treat them.

By storing water in the base/subbase and then slowly draining it through pipes, the design behaves like an underground detention pond with the added benefit of reducingcontaminants. A no infiltration retention design may be used for water harvesting. The water may be piped to an underground cistern for reuse on site. Harvested rainwater reduces landscaping water requirements and in some cases it can be used for gray water within buildings.

Geomembranes are a class of geosynthetic fabricated to create a sheet barrier that is relatively impermeable and is installed to prevent the flow of liquid or gas across that barrier.

Geomembranes can be manufactured from a range of polymers including polyvinyl chloride (PVC), chlorosulfonated polyethylene (CSPE), chlorinated polyethylene (CPE), or, more recently, polypropylene (PP), ethylene propylene diene monomer (EPDM), high-density polyethylene (HDPE) and linear lower density polyethylene (LLDPE), very flexible polyethylene (VFPE). Each of these polymers is unique and provides varying levels of resistance to acids, alkalis or petrochemicals. Some polymers can also function in extreme heat or cold. Normally, the surface of a geomembrane is smooth, but some sloped applications can benefit from a textured surface that provides greater friction with the adjacent geotextiles or soil.engineer2

Geomembranes come in a range of thicknesses depending on the polymers and the manufacturingprocess. For example, HDPE geomembrane is typically available in 40, 60 and 80 mil (1.0, 1.5 and 2.0 mm) thicknesses and in a range of roll widths. Geomembranes have different engineering properties depending on polymer type, thickness and manufacturing process. Typically the nominal thickness, density, tensile strength, tear resistance, dimensional stability and puncture resistance are provided in manufacturers’ literature and referenced in product specifications.

Geomembranes for PICP are typically fabricated on the job site and this requires cutting, fitting and seaming to create waterproof joints. Different seaming techniques are used depending on the polymer,environmental conditions and project requirements. Materials like EPDM and PVC are routinely seamed using adhesive or double-sided tape. Before two panels are joined, the areas to be joined are usuallycleaned and primed. HDPE and other polymers are typically welded together with extrusion welders or hot wedge welders. Seams for all materials should be field-tested to ensure their integrity, especially around underdrains penetrating the geomembrane. For smaller projects, it might be possible to have the supplier prefabricate the geomembrane to meet site requirements. Prefabricated geomembranes are typically delivered to the site folded on a pallet.

When preparing a site for a geomembrane application, remove rocks, roots, and other sharp objects from the subgrade that may damage the geomembrane during installation, aggregate compaction,or use. Such areas should be filled with dense-graded aggregate and compacted before placing the geomembrane over them. A layer of non-woven geotextile is commonly used to protect one or both sides of the geomembrane. The thickness of the geotextile is typically selected based on the materials placed next to the geomembrane and the importance of preventing puncturesof the geomembrane. Figure 2 illustrates a green alley in Richmondwith a geomembrane that is protectedby a non-woven geotextile before placing and compacting the subbase aggregate.

When designing a no infiltration PICP system, there are many factors that must be considered in selecting the geomembrane and protection materials. For most projects, consultation with an engineer familiar with the design of a geomembrane is recommended.


ICPI Releases Tech Spec 18

The Interlocking Concrete Pavement Institute (ICPI) has published the newest addition to its popular Tech Spec technical bulletins, Tech Spec 18: Construction of Permeable Interlocking Concrete Pavement Systems.

This bulletin is for contractors and project inspectors, and assists design professionals in understanding construction requirements for project specifications. Tech Spec 18 covers permeable paver components, benefits, recommended sites and important characteristics, sites to avoid, functional descriptions for full, partial and no exfiltration systems, design considerations and a step-by-step description of the construction process, which is also summarized in a convenient check list.

Permeable interlocking concrete pavement (PICP) is recognized by federal, provincial, state and municipal stormwater and transportation agencies as a best management practice (BMP) and low impact development (LID) tool to reduce runoff and water pollution. In addition, PICP offers unique design opportunities for reducing combined sewer overflows with green alleys and streets, as well as with parking lots and pedestrian surfaces. Tech Spec 18 addresses a growing need to educate contractors on installation best practices for this sustainable pavement system.