Transitional Space

The worlds of commercial and residential concrete paver installation are vastly different. Commercial jobs like parking lots and streets often require specialized equipment such as mechanized paver installation equipment and the financial resources to finance the longer period of time required to get paid for a job. In contrast, residential jobs are typically smaller in scale, with fewer stakeholders wanting answers, but where creativity is a driver for success. As a result, the great majority of contractors specialize in one area or the other, and few bid for both commercial and residential projects.

However, some have found a unique middle ground. Small commercial projects, such as business entryways or corporate courtyards, can provide a point of entry for the residential installer looking to expand into commercial work. These smaller commercial projects can be executed without specialized installation equipment, and often feature creative designs that are a residential specialist’s forte.

Gleason Works Entryway - 2
The 1,100 sf entryway courtyard for Gleason Works in Rochester, NY, featuring a 250 face foot wall, is the kind of small-scale commercial project ideal for residential installers to seek out as a springboard into the commercial world.

John Welch, owner of John Welch Enterprise outside Rochester, NY, is a residential contractor who recently expanded his business to include these types of small commercial projects. His company started developing commercial relationships by doing plantings and irrigation work for commercial properties, but they soon saw opportunities to bid on some hardscape projects as well. Rather than tackling parking lots and the like, his company focuses on specific areas like main entrances. “We sell our customers on the artistic value of what we’re doing, versus just being a functional entrance,” Mr. Welch says.

Mr. Welch prides himself on the artistry of his work, and the decisions his company makes when they tackle residential projects. With small commercial projects, Mr. Welch and his team can still cut and craft paver inlays by hand, allowing for much more artistic freedom. When designing small commercial entryways or courtyards, he maintains creative freedom, and the companies that hire him value his designs. As a result, Mr. Welch has developed a good reputation in the commercial world and a marketable portfolio for these types of jobs.Mr. Welch speaks to the benefit to small commercial projects where contractors often have some influence or complete control over the design and artistry versus larger commercial jobs designed by an architect or landscape architect. With large jobs such as parking lots, contractors are hired for efficiency rather than creativity, says Bill Gardocki, owner of Interstate Landscape Co. in Londonderry, NH, who has also done some small commercial jobs. “In the [broader] commercial market, you receive a plan and you bid on it,” Mr. Gardocki says. “There’s no creative element, generally speaking.”

Last year, almost 24 percent of John Welch Enterprise’s revenue came from commercial projects. This year, it’s up to 29 percent. “Once you get into these commercial areas, companies start to see you,” says Mr. Welch. Expansion into commercial work has been good for business, and the company’s growing reputation has attracted new customers every year.

However small these projects may be when compared to the larger size of most commercial work, they still have similar challenges, for example, how long it takes to get paid. “We don’t get paid nearly as rapidly,” Mr. Welch says. “The size and cost of the project is generally more, so we are trying to get a larger sum of money, and that’s a challenge as well.”

All things considered, that small commercial space between these two worlds might actually be a better fit for some residential contractors than commercial ones. Residential contractors may not need to invest in specialized equipment, and commercial installation companies focused on paving production may not want to engage in time-consuming custom detailing. Some residential contractors are likely poised to fill that sweet spot and reap the rewards. Mr. Welch profited from it, and other residential installers might find lucrative new business opportunities by following his lead.


The Icing on Top

Residential or commercial clients can be acutely aware of how tired-looking hardscape surfaces become over time. In some cases, an upcoming or recently completed sale of the property will prompt the owner to refresh unappealing drives, courtyards or walkways. Owners who are cost-conscious may look to concrete paver overlays as a less expensive solution that delivers the visual improvement they desire.

Contractors may also view overlays as a potential high-margin, lower-effort job, but many factors must be taken into consideration to ensure a comprehensive and accurate bid, and quality installation.


Prior to submitting a bid for the job, installers need to conduct a thorough assessment of the site. Evaluating the condition of the surface to be overlaid is, of course, the first step. It is best practice to have a pavement/civil engineer assess the quality of the surface, but property owners may balk at the cost associated with this, especially for a relatively small job, such as a driveway.

Asphalt or concrete surfaces with severe cracks or chips, or ones that show heaving, rutting or pumping, are not suitable surfaces for new paver overlays. Base surfaces with this degree of damage are likely near the end of their lifespan, and pavers applied over them will reflect the underlying damage and could fail within a very short period of time. In these cases, it is best to recommend complete replacement of the surface.

Contractors should also examine the base and subbase of the existing pavement. Signs of water trapped beneath the pavement or movement of underlying soils are usually visible at the surface as heaving or deflection in the concrete slabs or sections of asphalt. Again, paver overlays are not appropriate for these kinds of conditions and a total replacement should be recommended. If the base, subbase and old surface are in good shape, an overlay job can proceed.


Once the existing surface is deemed suitable for an overlay application, site evaluation continues with an examination of the surface thickness, grade, elevation, drainage and any incorporated structures. Be sure to explain the evaluation process to the client—particularly any changes in elevation or slope—to ensure complete understanding and agreement before work begins.

The existing surface should be smooth, with a surface tolerance of ±3/8 in. (10 mm) over 10 ft (3 m) to ensure even application of the bedding sand. If there are minor deviations in the surface, higher sections can be ground down. If the milling exposes cracks within the asphalt or concrete, those sections can be patched to make them conform with the rest of the area.

Use a transit level to measure the grade of the existing surface. Because the paver overlays will follow the contour of the existing surface, any minor adjustments needed in the slope can be accomplished by selectively varying the depth of the bedding sand. Keep in mind, however, that the compacted depth of the bedding sand should not exceed 13/8 in. (35 mm) in any given area.

Drainage will be needed for the bedding sand. For a short time after the overlay installation is complete, water will continue to move through the paver joints into the bedding sand. To direct this water out, drill several 2-in. (50-mm) diameter drainage holes through the existing surface at the lowest elevation. Fill the holes with ¼- to ½-in. open-graded washed, angular aggregate.

Plan for elevation transitions to adjacent pavement so that new and old surfaces meet exactly. In most instances, this will require an adjustment in slope over 10 ft (3 m) as the overlay pavers approach the pavement, and might necessitate removal of some of the underlying concrete or asphalt. In cases where the overlays will butt against stairs, the additional height of the overlay may decrease the height of the first stair riser, which might be a code violation and may present a hazard. One solution is to adhere pavers to the stairs as well to maintain the appropriate rise and run.

If another party, such as a utility company, state or local authority, is responsible for raising or relocating structures such as manholes, catch basins, utility boxes, or gas or water valves, be sure that they receive timely notification of the work plan and construction drawings with elevation changes clearly marked.


To prevent shifting of the outermost pavers, use edge restraints made of cast concrete, steel, aluminum or plastic, fastening them directly to the existing surface with expansion bolts (on concrete) or spikes (on asphalt). Place a 12-in. (300-mm)-wide strip of geotextile against the edge restraint, turning up a 1-in. lip to hold the bedding sand. In some cases, the paver overlays will butt against an existing curb. If the curb face is perpendicular to the surface, no new edge restraint is needed, but place the geotextile strip along the curb and turn up the edge as you would for the other edging. If the curb face is angled—as is sometimes the case on street-side installations—it might be necessary to saw-cut a vertical face on the curb.

Generally speaking, an underlayment of geotextiles would not be required on existing, relatively new asphalt and where there is little to no danger of bedding sand loss. For existing concrete, place a 12-in.-wide strip of woven geotextile over seams and expansion joints to prevent bedding sand loss.

Prepare the site for bedding sand by first setting up the screed bars. To help prevent wrinkling the geotextile as sand is being poured in, shovel a small amount onto the fabric in several spots to hold it in place while the dump truck moves across the site. Have the truck driver move in a single path, preferably in a straight line, and at slow speed to minimize disruption of the textile.

The bedding sand should conform to ASTM C33 or CSA A23.1 gradations with only 1 percent throughput in a No. 200 (0.075 mm) sieve. Aim for a depth of 1 in. (25 mm) in the field overall; but to allow for variation in the underlying surface, compacted thicknesses of 5/8 in. (16 mm) at minimum or 1 3/8 in. (35 mm) are acceptable. Screed to a smooth surface and proceed with setting the pavers.


A Foothold in Nature

A once-popular park in the center of Calgary, Alberta, received a reprieve from dereliction when 6,000 residents responded to a Calgary Municipal Land Corporation survey on re-development options. The overwhelming response was to return it to an island park oasis reminiscent of its fondly remembered glory days as a wooded campground and recreation site. Thus began the revitalization of the 31-acre St. Patrick’s Island Park on the Bow River in the heart of Calgary.

Unveiled to the public on July 31, 2015, the $20 million renewal of the regional park features restored natural habitat with native plantings and wetlands accessible by trail, a boardwalk and walking trails. A river channel was dredged and restored to its natural state to allow access for waders, water play and rafting, plus a woodland habitat was re-established for nesting hawks, owls and other birds. With the natural environment being the soul of the project, designers kept the human footprint light while providing an amenity-filled, family-friendly park that encourages year-round use by city dwellers. Amenities include play, picnic and viewing areas; walking, running and bike trails; pavilions surrounding two event spaces and pathways that can accept small (up to 1-ton) utility, maintenance and emergency vehicles.

“The project team took a biophilic approach in terms of development,” says Susan Veres, VP, marketing and communications with project owner Calgary Municipal Land Corporation (CMLC). “Biophilia, literally translated, means a ‘love of life’. The concept is based on the theory that there is an inherent human need to interact with nature. In fact, studies have shown that people’s physical, mental and spiritual well-being is tied to the natural environment. In the context of St. Patrick’s Island Park re-development, that means looking at the island from its natural state, its physical location in the Bow River, and how, from an emotional state, Calgarians wished to experience the park.”


The surface materials of choice for this island oasis include 65,000 sf (6,000 m2) of concrete paver ‘planks’ measuring 445 mm long, 100 mm tall and 70 mm wide, set in a running bond pattern with random color distribution in three grays. The pavers are prominently used in two key areas of the island: Confluence Plaza (an event pavilion and amphitheater area named for the island’s location at the confluence of the Bow and Elbow Rivers), and at the Seasonal Breach area near the landing of St. Patrick’s Bridge. St. Patrick’s Bridge opened in October, 2014, as a pedestrian and cyclist access route across the Bow River. Portions of paver pathways meander throughout the island. The design creates unique, seamless transition details in the many, varied edges where the pavers join the park’s other surface materials, including gravel and clay mix on trails and wood decking.


When starting on the island design, CMLC and city stakeholders were already familiar and comfortable with the aesthetic and practical benefits of concrete pavers, says Ms. Veres. The island project is part of a larger, 20-year infrastructure improvement program being delivered by CMLC throughout Calgary’s Rivers District Area in the east end of Calgary’s downtown. The lion’s share of CMLC’s work is a master-planned community called East Village, a 50-acre brownfield site reimagined for mixed-use, high-density development that serves 11,500 residents, and is planned in response to exploding city population growth driven by oil and gas development.

A key element of the East Village streetscape is about 31,000 square meters of L-shaped concrete pavers used to establish sidewalks and road carriageways with a cobblestone effect—the first large-scale use of concrete pavers in the city, says Ms. Veres. While the initial installation cost of the pavers was relatively high compared with some of the design team’s other options, that cost has since been more than outweighed by ease of repair and maintenance, and by the fact that the streetscape serves as a unique selling proposition to developers and residential buyers. “They’ve attracted interest, set a standard of quality we were seeking for this community, and helped set the tone for the larger project,” said Ms. Veres. After years of working on the East Village, CMLC’s contractors had a wealth of experience with the materials, she adds. “It was easy for us to imagine how the pavers might add to the experience and aesthetic of St. Patricks’ Island Park. We tested them and had success.”

Chosen in part for their experience with waterways, design firms W Architecture of New York City and Civitas of Denver envisioned a naturalized environment and modern amenities fitting together without too much visual contrast—a challenging design task, says Martin Barry, ASLA, associate with W Architecture. That led to the choice of paver planks for a linear look with texture created by a tricolor scheme, he explains. “It elongates the smaller spaces, while shrinking the scale in others. The result is some places have more of a feeling of expansiveness, where in others, there are big pauses.” While even longer pavers were an option, Mr. Barry says the paver length on the island project was limited to 18 inches to protect against potential cracking under occasional use by light-utility vehicles.

Pavers were also chosen for their ability to withstand Calgary’s climate, including bitterly cold winters and year-round sun. In addition to creating an even visual flow, the paver colors, in natural gray, medium gray and charcoal, were chosen partly for their high reflectivity to minimize heat-island effect, Mr. Barry says. The system is also designed to be entirely permeable, accepting and filtering stormwater just as the surrounding environment will do naturally. Calgary is flood-prone with the Bow and Elbow rivers running through it. While it is unlikely that St. Patrick’s Island will find itself underwater again anytime soon—as it did in a massive 2013 flood caused by a 100-year weather event—the permeable paver system fits neatly into the larger project’s necessarily water-friendly design, say stakeholders.


The paver design creates appealing, seamless connections to natural materials, such as wooden decking and trail surfaces, Mr. Barry says. “The flush transition from hardwood tropical decking onto the concrete pavers, and the color variation between the two, is really quite beautiful. Where the pavers intersect with trails of decomposed stone, a very nice transition is achieved with the soft material butting up against the hard.”

“The choice of a running bond, random color distribution was a core component of these many, varied transitions when it came to installation,” says Mr. Barry. “We used these pavers [in another project] with a stacked random bond color distribution, and it was tough keeping the pavers in a straight line on a big plaza,” he explains. “When using linear pavers, I recommend being careful of the kind of alignments and patterns, as they can be limiting. Using the running bond on St. Patrick’s Island allowed us much more flexibility.”

Local landscape architecture firm IBI Group collaborated with designers on the choice and placement of native plantings and other softscape materials. They were pleased with how the pavers’ flexibility allowed edges to blend well with the natural environment, says Garth Balls, senior landscape architect, associate, IBI Group. “We wanted the natural vegetation of the island to be the focus for visitors. There is very little manicured grass on the island. Where the pavers end and the landscape touches, the long, narrow paver creates an attractive pattern that is very compatible with the plant material and doesn’t draw too much attention to itself.”


Experienced with previous paver installation in the East village project, Marmot Concrete created attractive transitional edgings in the park. After excavation of some areas, the base installation was a relatively simple project, says Cameron Smith, project foreman. “There are a lot of underground water systems with drain rock and river stone on the island—all good building material. We just had to strip off silt and loam and away we went, with the base and bedding.”

Then there came a learning curve with hand installation due to the random paver pattern. “We wanted nice straight lines and bisecting angles, while keeping the pattern tied together when we went around obstacles. Working with long, skinny pavers and cutting that with steep angles made that a challenge, but it went well,” he says. On Confluence Plaza, for example, the pavers flow around the amphitheater and stairs, and tie to precast seating. Paver-surfaced finger pathways meander through the park as well as tying into the pedestrian bridge at the island’s west end where they direct visitors in two directions, to an elevated breach walk and a low-water crossing.

The Marmot team experimented a bit with some patterns prior to getting started, Mr. Smith adds, but in the end the designers chose the random pattern, so the logistics were pretty simple: Due to the size of the project, manpower needs were significant. Marmot had 15 workers installing pavers full-time prior to the July grand opening.

“To know the island [before] and to know it now—the change is truly remarkable,” says Ms. Veres. Adds Mr. Barry, “We are calling this project the ‘emerald jewel’ in the Bow River and of downtown Calgary. It’s great to have an environment that provides hard plaza spaces for recreating, and having festivals and fairs. We were able to concentrate those and use more open space for looking at the city views, standing where the water comes through the site, or tobogganing in the winter. It’s remarkable to be involved in a project that gives such a variety of spaces for Calgarians to enjoy year-round.”


Learning Curve

The ICPI Foundation for Education and Research awarded the Landscape Architecture Foundation (LAF) a three-year, $75,000 grant to enhance the Landscape Performance Series (LPS), an online interactive resource that helps designers, agencies and advocates evaluate performance, share best practices and make the case for sustainable landscape solutions.

Launched in 2010, showcases evidence-based environmental, social and economic benefits of landscape by sharing information and innovations from the fields of design research and academia, as well as industry and professional practice. Much of the site provides case studies demonstrating landscape performance with detailed information on performance assessment of economic, environmental and social benefits of landscape designs with the human and natural systems with which they interact.

Besides significant visibility for the ICPI Foundation, the grant includes input from the ICPI Foundation by curating case studies with segmental concrete pavement systems and by providing product information. The site’s content will be filterable by landscape system, such as interlocking or permeable interlocking concrete pavements. The most significant aspect of the program will be a new training section that the ICPI Foundation will develop with LAF, “Designing for High Performance,” with the first learning module focused on segmental concrete pavement.

Moreover, the ICPI Foundation has opportunities to share their research and sustainability initiatives within the LPS. This will be in the form of blog posts or a curated “collection” of content as part of the new website. Since its inception in 2000, the ICPI Foundation has sponsored several research projects to better define the economic, environmental and social performance of segmental concrete pavements. The LAF website provides significant visibility for the ICPI Foundation with landscape architects and academics via a website that receives over 90,000 visits annually.


Grabbing Wallets

When introduced in 2014, the U.S. Green Building Council’s LEED v4 heightened awareness of environmental product declarations or EPDs. Among significant changes to the LEED Materials & Resources credit criteria, LEED v4 now bestows a modest one point for projects with at least 20 EPDs from different construction material manufacturers. Given that buildings and sites typically contain thousands of products, this seems a small requirement by LEED v4.

One intent of this credit is to raise awareness of EPDs among construction material suppliers. This requirement has led many construction materials industries to first create product category rules (PCRs) according to ISO standards. PCRs prescribe requirements for defining the impacts of manufacturing a product, as well as outline the elements of a life-cycle assessment (LCA) of environmental impacts from manufacturing. The LCA forms the basis for creating an EPD.

EPDs list environmental impacts from manufacturing a product. They have been compared to reading a nutrition label on food packaging. Rather than fat, carbohydrates, proteins and vitamins, EPDs list the following impacts: global warming potential (carbon emissions); sulfur-dioxide, ozone and smog-type air pollutants; total energy consumed; use of renewable resources; depletion of non-renewable natural resources; nutrient emissions into waterways; and fresh-water use.

A practical yardstick for measuring these impacts is typically a unit of volume or mass of the finished construction product. For segmental concrete paving units, this is a cubic yard or meter of concrete. Most impacts per cubic yard of concrete are from carbon emissions due to producing cement and from generating electricity to run a manufacturing plant. Obviously, the energy source to make cement and electricity influence carbon emissions. EPDs favor hydroelectric, nuclear, wind and solar energy with lower carbon emissions compared to coal, gas or oil-fueled sources.

Now that ASTM issued a PCR for segmental concrete pavement products, it’s up to manufacturers to conduct LCAs, then produce and publish EPDs on their products. While the market isn’t consistently or even intermittently demanding EPDs from concrete paver manufacturers, the industry is preparing for the inevitable change. California manufacturers will likely be the first with EPDs, since that state imposed a legal mandate to trim carbon emissions. To assist the education process, the ICPI Foundation for Education & Research recently developed a guidebook for manufacturers on creating LCAs and EPDs. ICPI also developed a manufacturing material and energy-use inventory spreadsheet tool for its members.

Comparing EPDs among manufacturing segmental concrete paving products, asphalt and ready-mix concrete requires nearly equivalent PCRs. The asphalt industry will weigh in when their PCR is completed late this year or next.

While LEED and other sustainability evaluation tools have taken modest steps to raise EPD awareness in the North American construction world, where are EPDs ultimately going? They will become a critical source of data that will eventually feed into evaluating environmental impacts from a product’s construction, life and disposal/reuse. This is already happening in the building design world. It’s just starting in the pavement world.

Segmental concrete paving products are in a unique position to offer lower environmental impacts by not requiring huge paving machines and concomitant fuel consumption during construction. During their life, segmental concrete pavements offer immediate reuse in-service, a significant benefit for cities. Asphalt and cast-in-place concrete do not; those materials are removed and landfilled or later recycled.

Quantifying differences among construction, lifetime and end-of-life impacts will become increasingly important to municipal transportation agencies in the coming years.

Aggregates supplies are decreasing in some regions. Asphalt isn’t cheap. Transportation agencies are expected to build, maintain and rehabilitate pavements with less money and make them last longer.

Like Europe, agencies here will eventually move toward bidding material, construction and project maintenance life-cycle assessments. Maintenance pricing and LCA bids will spawn risk assessment/financing companies. (Maintenance price bids are already happening with some ICPI members selling permeable interlocking concrete pavements.)

All of these tools will ultimately save agencies money. LCAs will grab their wallets. That will get their attention.