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.


The Great Enheightenment

In recent surveys, readers have asked for instructional articles with practical knowledge they can use on the job. In response, Interlock Design is pleased to present this first installment of its new how-to series of feature articles that will run throughout the year. We welcome reader feedback and invite you to contact us at with any suggestions or topics you’d like us to cover in the new how-to series.

Why a Raised Patio?

As this issue’s cover story explains, residential outdoor living is a booming market for the hardscape industry. An integral component of an outdoor living space is a raised patio.

Traditionally, a raised patio allows movement from house to backyard without a change in elevation. A homeowner steps out the back door and into the outdoor living space as easily as walking from one room to the next inside the house, creating a seamless transition from interior to exterior space.

Initial Precautions

“If not done properly, a raised patio can do significant damage to the building that it’s constructed against,” says ICPI Director of Engineering Robert Bowers, P. Eng. The main factors that can cause damage are moisture accumulation and the increased lateral load placed on the foundation, and possibly on exterior above-grade walls.

Most exterior above-grade walls of a house are not designed to have moisture continuously against them, explains Mr. Bowers. Whether they’re brick, wood siding, vinyl or another material, these exterior walls are designed to resist water and shed it—to get wet and then dry out. They cannot withstand a continuously moist environment. Placing compacted soil against these types of walls can trap moisture, resulting in mold, decay and deterioration.

Regarding foundation walls, in most cases they are constructed to bear the weight of the supported structure, the lateral pressure from the soil and not much more. By constructing a raised patio, the lateral pressure against a foundation increases. This presents an increased risk of blowout and basement wall collapse, because the increased load to the wall is not counterbalanced. This is called an unbalanced fill condition. When taking on an unbalanced fill project, an engineer should be consulted to ensure the stability of the project. Additional reinforcement of the foundation wall is sometimes necessary. The cost of the engineer’s involvement will increase the cost of the construction, so it’s important for contractors to include this in the price of their proposals.

 “A homeowner should be able to appreciate it,” Mr. Bowers says, “if you say, ‘Hey, I’m concerned that we don’t damage your house in any way and I’d like to have a professional engineer tell us the best way to do this.’”

At the outset of planning, be sure to thoroughly document the existing conditions of the site. Take photos of the exterior walls, the foundation and the basement walls inside and out, carefully inspecting for cracks, bulging and any signs of dampness or water damage.

Design Considerations

The most effective way to raise a patio adjacent to a building is with a retaining wall (aka stress relief wall) that faces the building, offset from it by 3 to 4 in. This creates an air gap that prevents the patio from touching the building’s exterior cladding and also allows airflow so any moisture that gets in can dry out (See Figure 1). Additionally, the air gap prevents a raised patio from covering up weep holes. Covering weep holes compromises the exterior above-grade wall venting system, leading to deterioration and potential collapse. For this reason, covering weep holes is a building code violation. At the top of the air gap, cantilevered pavers and screens are common solutions to prevent debris from falling into the gap. A drainage system at the bottom of the air gap is also required. Another option is applying aluminum flashing against the house. This surface, however, cannot block weep holes designed to wick moisture from the walls.

The higher the patio is raised, the greater the complications and potential risks to the foundation. Most homes are constructed with 8 to 12 in. of foundation wall above grade, atop which sits another 12 in. of floor joists. That means the threshold of the back door is typically 20 to 24 in. above grade. For every foot of elevation a wall is built up, roughly 50 to 100 pounds of additional load is applied to the foundation walls. Depending on a number of conditions, it could be even more.

Coincidentally, a raised patio height of 20 to 24 in. is a gray area for determining if additional measures are required to reinforce the foundation wall. For any patio raised above 24 in., it is recommended to have an engineer review the design, test soil quality, evaluate foundation walls and make recommendations.  Heights of 20 in. or less generally carry less risk in relation to the loads. Ultimately, each contractor must decide on his or her level of comfort and corresponding liability.

“If you think there’s the slightest possibility you might need an engineer, then you need an engineer,” Mr. Bowers says. “I can’t tell you how many calls I get from contractors who say, ‘I’m not sure but I think I might be doing something that requires an engineer.’  They describe the situation and yes, they should’ve had an engineer involved weeks ago.”

Local building codes also come into play at heights around 24 in. or greater and when adjoining the raised patio to a building exit like a back door. Every building code has specific requirements for steps including tread depth, riser height and pitch, as well as for hand railings and guards. Because many aspects of raised patio construction are governed by building codes, raised patio construction often requires first obtaining a building permit.

Raised Patio Construction

Raised patios are constructed using three basic components: walls, flatwork and steps. But before building anything up, the ground must be broken.


When new home construction is completed, often the soil against the foundation wall is excavated backfill of the soil consisting of silty, clay soil unsuitable for the subgrade of a raised patio. A soil probe or test pit will confirm this and is recommended to determine soil type and quality. A common way to reduce the lateral load applied to a foundation wall is to remove poor quality soil and replace it with a higher quality dense-graded, crushed stone aggregate. As a rule of thumb, the height of the patio determines how deep to excavate and how far out from the building foundation. If a raised patio will be 48 in. (1.2 m) high, dig down 48 in. (1.2 m) and out from the building the same distance.

Subbase, Drainage, Base

Dense-graded, compacted aggregate is commonly used for the base of the wall and the raised patio. For some projects, flowable fill may be advantageous because it’s lighter and does not require compaction. However, it can be more expensive to install and may require time to cure.

Once the subgrade and base for the wall are set, install a 4 in. (100 mm) diameter perforated drainage pipe along the length of the wall that slopes to a drain. For the drainage layer above the drainage pipe, use open-graded, compacted aggregate with ¾ in. (19 mm) minus clean stone (See Figure 2).


When using segmental retaining wall (SRW) units to raise a patio, a conservative rule of thumb is that the maximum height of the wall should be approximately twice the depth of the SRW unit. For heights three times the depth of the SRW unit or greater, geogrid should be used to help stabilize the wall. Most building codes require walls over 48 in. (1.2 m) in height to be engineered, and some jurisdictions have set limits even lower.

A conservative initial design incorporating geogrid could specify continuous layers every 12 to 16 in. (300 to 400 mm) vertically with a length equal to the height of the wall, and not less than 4 ft (1.2 m). This design would only be suitable for typical conditions: dense graded aggregate backfill; pedestrian-only loading with no slope or terraced wall above; a stable, undisturbed subgrade to a maximum total height of 8 ft (2.4 m). If these typical conditions do not exist on the site, or the decision is made to optimize the design, an engineer should be consulted to develop the initial design.


Every building code has requirements for steps. For outdoor applications, a common pitch requirement is 6:12: a 6 inch (150 mm) riser and a tread depth of 12 in. (300 mm). Maximum riser heights of up to 8 in. (200 mm) may be permissible, so check local building codes. The steps must have a consistent tread depth and riser height to prevent a tripping hazard. Complete compaction of base material is extremely important. Flowable fill or a well-compacted, cement-treated aggregate can help minimize the potential for settlement.

SRW units (Figure 3) or concrete pavers (Figure 4) can be used to construct steps. Either way, choose a material that has freeze-thaw durability. Snow removal and deicers can destroy concrete materials not manufactured to freeze-thaw resistance. Some SRW systems have cap units that are not meant to support regular pedestrian traffic, so be sure to choose the proper units if using for steps. If pavers are selected for the steps, it is necessary to build the base out of concrete to prevent “roll over” that occurs if paver steps are not properly supported.


For patios with elevations greater than 24 in. (600 mm), most building codes require a guard or handrail, including minimum height requirements, as well as specifications for resistance to lateral loads. For code compliance, the railing, mount and foundation all must resist the applied load. Generally, there are four types of mounts used to connect the post to the stabilizing foundation: surface, core, side and direct.

Surface mounts are common but also typically the weakest. A plate is welded to the bottom of the post and then connected to the top of the retaining wall with lag bolts or self-tapping concrete screws. Core mounts involve drilling down 18 to 24 in. (450 to 600 mm) into the retaining wall and grouting or epoxying the post directly into the wall. Core drilling can be time-consuming and costly and risks splitting the SRW units under certain conditions in freezing environments. While core-drilled guards are potentially more stable than surface mount guards, neither should be relied upon as the only means of securing the guard.

Side mounts attach handrails to the face of a side wall. When side-mounted handrails are combined with a guard system, they contribute to the stability of the entire guard assembly. The most effective way to secure a guard system is with the fourth type, a direct mount, which attaches to a solid fixed object like a building or caisson (See Figure 5).

Site Prep

The main task in job layout is transferring the final design from paper to the site. Verify access and staging areas; identify slopes and drainage conflicts; install erosion control and containment measures; and provide protection for trees, plantings and structures. Confirm the location of all utilities and buried utility lines, making sure everything is clearly marked. Outline the extent of excavation and the patio, install string lines, and designate finished elevations with stakes, string lines and markings on adjacent structures. Make plans for equipment storage and vehicle parking. And always maintain a clean, organized site to make a favorable impression.

When defining the elevations of a project, identify the critical elevations on existing structures like a doorsill. Typically, critical elevation determines the finished elevation, so it is necessary to calculate backward from the finished elevation down to the starting elevation. Repeat this calculation in several locations on-site and double-check them.


Care must be taken when compacting adjacent to a foundation wall; excessive force may cause cracking. Less force can be used by placing soil in thinner lifts. For the first course of SRW units, dense-graded aggregate base should be compacted to a minimum of 98% standard proctor density (SPD). Although industry guidelines call for 95% SPD for the fill behind the retaining wall, ICPI recommends 98% SPD to minimize the settlement of the pavement surface above. It is important to watch the alignment of the SRW units to ensure they are not pushed out of alignment or rotated forward during compaction.

For bases and fill, in addition to the flowable fill alternative previously mentioned, geotextile or geogrid, cement-treated base (CTB) and asphalt-treated base (ATB) are also options. Installers who have limited experience with these materials and methods should receive technical support prior to selection. A geotechnical engineer’s input may also be necessary to determine the strength of the subsoil and the extent of remediation required.

Raised patios also require adhesives for retaining wall caps, treads and other materials. Adhesives that remain slightly flexible after curing are preferred. Though mortar can be a cheaper option, its use is not recommended in areas with freezing and thawing conditions.

Close Out

Equipment removal and cleanup are standard operating procedure. After running down punch-list items and performing final inspection, secure a certificate of occupancy and final payment. As a courtesy, provide the homeowner with spare pavers, sand and cleaner. Photograph the completed project for the company’s portfolio and be sure to write a thank-you note for a high-dollar job.

Continuing Education

The information provided in this article is from the ICPI Advanced Residential Paver Technician Course manual. To sign up for this course or any other offered by ICPI, visit


Backyard Project Boom

Some spa owners might be jealous of the newly revamped backyard of a Wayne, NJ family: 5,000 sf of outdoor living space, complete with an elevated patio area, pool and hot tub lined with natural rock, a waterfall bubbling gently down from a walkway above, and a cozy fire pit tucked off to the side. The era of kiddie pools, Coleman grills and fold-up lawn chairs may be officially over.

“Our backyard residential projects are all becoming high-end, and even people who are watching their budgets are asking for elements like fireplaces, outdoor kitchens and extensive living spaces,” says Joe Monello, owner of New Jersey-based Monello Landscape Industries. The recent project in Wayne makes significant use of hardscape, with concrete pavers playing a major role. Four different sections on the project — dining, pool entrance, lounging and fire pit — each used a unique paver style to differentiate one space from the other, with a repeating border that brings the hardscaped area together aesthetically.

Currently, Mr. Monello is working on several similar projects, including one that involves about 7,000 sf of concrete pavers. He certainly isn’t alone in garnering more extensive backyard projects like these. The trend is toward elaborate, sumptuous living spaces that replicate and expand indoor layouts, complete with a kitchen, dining and lounging areas, and a fireplace. “There’s no question that this is going to continue,” he says. “If anything, these projects are just going to keep getting bigger.”

Going Backwards

The shift toward larger backyard projects comes as the result of several factors, including a continuing interest in staying home and connecting with nature. Even though the 9/11 terrorist attacks happened over a dozen years ago, the dramatic move away from travel as recreation never really returned in a big way, notes Justin Hampton, co-owner of Paver Designs in Omaha, NE. And the sputtering economy of recent years has put “staycation” in the American lexicon firmly if not permanently.

“Instead of going on vacations, people learned how to stay home and have fun,” he says. “They’re turning their backyards into places to hang out. They’re going from a small patio or deck to grill islands, pizza ovens, seating walls and fire pits.”

Most of these projects incorporate several natural elements like fire, water and stone, as well as edible plants like grape arbors or herbs, says Julie Moir Messervy, a landscape architect based in Vermont who helms JMMDS, a creative design firm. “I’ve been pushing for people to put these things in their front yards and actually talk to their neighbors,” she says. “But there’s a sense of privacy in the backyard, and intimacy when you’re entertaining.”

Another part of the reason for the larger scale is lower cost compared to renovation, adds Frank Gandora, president of Creative Hardscape Company in Englewood, CO. To build an addition onto a home is usually around $300 per sf, he says, but for 10 percent of that price, a homeowner can have a large outdoor space for entertaining.

Mr. Gandora experienced this phenomenon firsthand. He spent almost $100,000 to refinish his home’s basement but less than $20,000 for a sumptuous backyard patio area. Where do guests prefer to spend their time? “Everyone wants to be outside, it just has a better feel to it,” he says.

The recent recession also reduced material costs, notes Jeff Zock, a landscape architect with Ryan Hughes Design in Florida. That incentivized homeowners, prompting them to increase the scale of outdoor projects. The recession made people retreat from interior renovations and put funds toward backyard projects instead. As the economy has improved, those projects got larger and more elaborate, Mr. Zock says. “People felt like they couldn’t justify remodeling, but they could see the sense in spending money on outdoor spaces. As a result, there’s been a huge surge in people wanting to invest in their backyards.”

Then, there’s Pinterest. More than any other social media site or marketing campaign, the online bulletin board has driven interest in backyard landscaping and remodeling. “Basically, people spend hours on that site getting ideas,” says Mr. Gandora. “Then they go to Google and spend more time looking at separate features, like fire pits or concrete pavers. People used to want to keep up with the neighbors. Now, they want to keep up with everybody on Pinterest.”

Bigger is Better

The trend many contractors and landscape architects are noticing is more larger pavers and slabs that require special handling and installation to prevent cracked units. Big pavers and slabs give a more natural look, believes Mr. Gandora. “The sense of scale is bigger, so what we’re seeing is a preference for bigger pavers,” he says. “If you have a very large project with smaller pavers, it can tend to look busy, and homeowners don’t like that, especially with so many elements in the space.”

Mr. Gandora thinks the paver industry may see issues with this trend in the near future. If homeowners start asking for larger pavers on driveways, they won’t work well there. Another disadvantage to larger pavers and slabs is weight; some can weigh up to 60 pounds, requiring specialized equipment to place them. But larger pavers are bringing advantages as well, Mr. Gandora says. Since each paver or

slab takes up more area, they install faster, which increases production efficiency. They also create an expansive aesthetic similar to natural stone, he adds.

Addressing Challenges

With the trend toward large outdoor residential projects, particularly in backyards, unique challenges emerge. One of the major difficulties can be access, especially with homes that have landscaping or narrow passageways along the sides of a house. That can increase a project’s cost because it takes more time to get materials into the backyard, says Mr. Hampton. For example, on a recent backyard project that involved a grill island, fire pit, retaining wall and extensive pavers delivered along the side of a mansion-style house, Mr. Hampton and his team couldn’t use a skid loader, so they used smaller equipment that required more trips. Overall, the project took five weeks, which was longer than it would have been with better backyard access.

But the extended timeframe became a positive, Mr. Hampton says. As the crew worked, the homeowner kept adding to the project, wanting more pavers and additional features. Grades are another challenge with backyard projects. People often will want their hardscape floor to meet the back door or existing patio, but a contractor has to figure out how to create enough slope away from the house to prevent water problems. That usually means putting in more hidden drains and finding an appropriate area where they can empty.

Looking Ahead

Despite some of the challenges that backyard projects present, many landscape architects, designers and contractors expect these outdoor living spaces to get even more extensive, especially as the economy strengthens and more of the population ages. “Empty nesters are really taking hold of this trend,” says Ms. Messervy. “They’re creating these backyard-homestead kind of spaces, where they have an appreciation for the land and nature. They find ways for their backyards to simply work better for them.”

The backyard is no longer a mere grass patch the kid down the block grudgingly mows each week. These days, that space is a place as vital and lively as any indoors. In some cases, it’s even more enticing than hanging out in the kitchen. Messervy says, “People love what they can create for themselves in their backyards, and it doesn’t matter where they live or whether it’s winter for six months of their year. They all want to be outside.”


Green Alleys of St. Louis

Taking cues from the successes of projects in cities like Chicago, St. Louis has installed several green alley projects since 2007 utilizing permeable pavers and interlocking concrete pavement. The Tower Grove Heights Green Alley Paver Project was completed in two phases from 2011 to 2014. It updated 400-year-old alleys with permeable pavers through a federal Community Development Block Grant, a state Department of Natural Resources grant, and local tax-based funding. PICP was used to reduce stormwater runoff and maintain the historic appearance of the alley, originally laid in brick over clay.

In 2009, the City of St. Louis commissioned a Pilot Green Alley project using donated materials and labor. Three alleys were installed that year with pervious concrete, porous asphalt and PICP. The performance of the city-owned alleys is being evaluated over time. All of these are built over open-graded aggregate reservoirs, allowing stormwater to drain through the system per the City’s specifications.

“We helped fund a portion of them because of the experimental nature of the materials at the time,” says John Grimm, of the Metropolitan Sewer District. St. Louis also used tax funds for the $41,000 Cherokee Green Alley Concrete Project, a 150-ft long by 12-ft wide alley completed in 2009. The pilot project’s outcomes are still being tested, with MSD conducting a report on flow measurements scheduled for completion at the end of 2015.

Green alleys are not unique to St. Louis, but the city’s history and layout with centuries-old alleyways and roads lends to more paver installations in the future, Mr. Grimm says. “There are some suburbs that have alley arrangements, but they are not as prevalent,” he says. “It’s mainly particular to the city.” 

return to River City Green


David Quinn, ASLA

David Quinn, ASLA, Sales, Angelus Block, Los Angeles, CA


ICPI’s efforts include the development and support of industry research, technical resources, university courses, specs and standards, contractor training, and marketing. Looking back at the Institute’s 20-year history, which of these efforts have been the most successful?

In looking back at the 20-year history of the ICPI and my own 18-year history in the paver industry, I would say the most successful effort has been in the technical resources from ICPI.

Any new person to this industry can quickly understand the advantages, performance, and function of ICPs and PICPs by reading and understanding the technical resources. This allows them to confidently carry that information to market, and provide the designer with valuable information instead of a sales pitch.

I have used the Tech Specs [technical bulletins] many times to provide information from ICPI, giving designers confidence that they are specifying the product and system correctly. Recently, the industry research has been very successful in providing information to engineers, so that they may specify the products with confidence. This has particularly been of value on PICPs where engineers have been slow to embrace this new technology and the research has been able to validate the ICPI’s design recommendations.

Another major benefit that ICPI provides is access to industry people and information, which have allowed for me to become a technical resource to local designers. There’s enormous advantage in talking with other members and finding out what trends they see, and what’s been successful in their markets.

We are all aware of the widespread use of segmental pavements in Europe compared to North America, understanding that there are centuries of tradition behind this widespread use. What do you think will accelerate acceptance here in North America?

For pavers to accelerate acceptance in the market there has to be an understanding of life cycle value, particularly in the municipal and commercial market by the decision makers and engineers. As more municipalities and commercial projects use programs such as LEED or building codes like CALgreen (California’s Green Building Code) which have a greater focus on life cycle, they will begin to see that they are not only green in the environmental sense but in the green financially with lower maintenance costs, lower repair costs, and longer performance with the use of ICPs and PICPs.

From a personal perspective, what are the main benefits of your ICPI participation?

The number one benefit to participation in ICPI has been access to industry people and information that has allowed for me to become a technical resource to the local designers. Also there is the benefit of talking with other members and finding out what trends they see and what has been successful in their markets.

Where do you see the industry in another 20 years?

In 20 years I see the paver industry having a larger share of the municipal and commercial markets. ICPs and PICPs will continue to prove their value as durable, functional pavements and with advancements in concrete technologies they will be more efficient, cost effective and environmentally responsive, leading to their greater acceptance and usage.

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Dave Hein, P. Eng., VP and Principal Engineer

Dave Hein, P. Eng., VP and Principal Engineer, Applied Research Associates, Toronto, ON


What trends have you seen in the past few years that could contribute to the increased use of concrete pavers in North America?

Definitely we’re seeing stormwater management and environmental awareness as major trends that are driving increased use. Sustainability is a big topic right now in all industries, and that makes it easy to talk about all the benefits that concrete pavers offer when you consider their advantages in terms of sustainability.

Also, I think some cities are beginning to see the differences between using asphalt and concrete versus using permeable pavers, and they’re hearing about the success other cities have had with pavers. The performance with a surface like asphalt is affected by how it’s applied, and that can be frustrating for city engineers. Also, you can’t test concrete or asphalt before you put it on a roadway, the way you can with pavers. So, I think all of those add up to more awareness and higher usage.

Another big trend could be the use of pavers in countries like Bolivia and China, where it’s relatively inexpensive to get into the business and you can lay the pavers by hand. That’s leading to major employment opportunities, especially for women in South America. As local municipalities begin to see that kind of usage increase, I think it’ll have an effect on what happens in North America.

From a personal perspective, what are the main benefits of your ICPI participation?

My history with the ICPI goes back 20 years, when I was approached by David Smith while I was at a conference. We talked about whether I would write a technical manual, because they wanted to use paving stones for an airport. I thought it was a crazy idea, but I did it anyway. I got input from ICPI members and technical folks and it turned out to be a pleasure working for these guys.

I think back then and now, they’re just out there trying to get the word out about using more paving stones. They’re meticulous in ensuring that standards are high. The bottom line is the barrier to get into this industry is not that high — you can buy a machine and off you go. It’s an exciting, accessible industry, and that’s creating numerous companies and each has its own agenda, but ICPI brings them all together. 

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Permeable Design Pro Upgrade

Permeable Design Pro, a software application for hydrologic and structural design of permeable interlocking concrete pavement, now features CAD drawing output (see example drawing). Drawings are generated by the program after calculating the subbase thickness for water storage and subgrade infiltration, as well as the required subbase thickness to support anticipated traffic. The program automatically selects the thicker of the two subbase solutions and presents the CAD drawing from a menu selection. The drawing can include an underdrain, geotextile, and an impermeable liner if no infiltration into the soil subgrade is desired. The CAD drawing also specifies the height of the underdrain outlet, if the designer indicates this in the program, as a means to detain some water for infiltration.

Also, the user can modify the CAD drawing by changing the subbase thickness and the underdrain pipe diameter, as well as the presence or absence of geotextile or an impermeable liner. The CAD drawing can be saved as a .dwg file for use in project drawings or submittals.

Permeable Design Pro can be downloaded from for a 30-day free trial. The purchase price is $190 per license with a discounted price of $95 for design professionals and ICPI members.

Permeable Design Pro

Permeable Design Pro software now features CAD output of design solutions for permeable interlocking concrete pavement.


Ed Fioroni, VP of Marketing

Ed Fioroni, VP of Marketing, Pavestone, Dallas, TX


How has ICPI helped to accelerate the acceptance and use of concrete pavers?

ICPI has been outstanding at providing technical support and standards that we all have to follow, which puts all manufacturers on equal footing.

Another major contribution in accelerating use of concrete pavers has been ICPI’s strong representation with government, to make sure that laws don’t affect the industry in a negative way. For example, keeping an eye on potential legal issues that might crop up from laws that mandate silica content in products.

Thirdly, the organization has come up with some strong marketing ideas that manufacturers can use, especially in getting architectural engineers and city planners to listen to us. That’s helped to get a foothold in the commercial and municipal arenas.

All of these are important because when you look at Europe, there’s such widespread use of segmental pavements there compared to North America, but they have the advantage of history. Pavements have been used there for centuries, and people are used to seeing roads and other surfaces with pavers, which leads them to want that same look for their homes or businesses.

We don’t have that kind of widespread use that inspires people to ask for pavers for their own projects, so ICPI efforts become incredibly helpful for creating awareness, and providing standards that advance the industry forward. Their efforts are an asset for all of us as we try to duplicate Europe’s success. The only way we can get anywhere close to their level — and I’d be happy with even half their square-foot-per-capita numbers — is to keep increasing awareness. I think we’re on the right track, with ICPI thinking strategically.

From a personal perspective, what are the main benefits of your ICPI participation?

Obviously being a professional research guy, I really enjoy the exchange of information that you can have as an ICPI member. You meet people in the same industry at events, meetings, dinners, and you have the chance to talk with top contractors and distributors. That creates benefits you can’t even explain. As a past chairman, I think it’s made me a better person. I learned to be a better leader through that experience.

What trends have you seen in the past few years that could contribute to the increased use of concrete pavers in North America?

The fact that we’re environmentally friendly will make permeable pavers major for us. The government will be mandating zero runoff and permeable pavers offer tremendous opportunity for meeting that goal. Residential should be important, since pavers are going into patios, pool decks, and outdoor living. What we need to do is help homeowners see pavers as an option for their driveways because that’s a big area where we can increase awareness.

Where do you see the industry in another 20 years?

Our goal will be to duplicate European success, and to go in that direction. The only way we can get that done is by increasing awareness in the commercial world, because once we do that, residential will follow. I think we’re on the right track, and that we’ve changed our way of thinking strategically. But pavers in the U.S. are still thought about in an aesthetic way, and in Europe, it’s considered functional. So, in the next 20 years, we need to be closer to getting people to think that way here.

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Chuck Taylor, Commercial Hardscape Advisor

Chuck Taylor, Commercial Hardscape Advisor, Oldcastle, Dayton, OH


What advice would you offer the next generation looking to follow in your footsteps?

About 30 years ago, I was just starting out in this industry and I had a friend ask me why I’d chosen to get into this field. I told him that it seemed to be an excellent industry for young people because it was still growing, and it had huge potential.

Now, when I’m not so young anymore, I can still say the same thing. I believe that this industry offers a great opportunity to build a future, not just for yourself but also for your family. My sons are in the business, and my nephew, and I expect the generation after them will also consider being in this business because that opportunity for growth still remains.

In addition to making a living and being in a solid industry that’s on a growth track, I’d tell anyone looking to follow in my footsteps to remember that this is a field that can make you proud. I know that I’m proud to be involved in it. When I started, my mission wasn’t just finding a career, I wanted to make a difference in the world, and I feel like I’ve done that. I’m still doing that. This is a way to address storm water management, and create more sustainable systems that are important for clean water. I look forward to seeing the impact of the next generation.

We are all aware of the widespread use of segmental pavements in Europe compared to North America, understanding that there are centuries of tradition behind this widespread use. What do you think will accelerate acceptance here in North America?

Well, the European culture has definitely had a head start, since they have so many roads built with stone. If you look at a place like Holland, with its high water tables, they use segmental pavers that can be moved every 10 years. In general, Europe just tends to be more sustainable in their thinking. I don’t think we’ve embraced pavers as a utility here the way they do in Europe, to many people here, pavers feel more like an accessory.

Another challenge is that asphalt here has always been popular because it’s cheap, but the problem is that it’s expensive to maintain. We just haven’t had the level of educational awareness needed here, but people are beginning to recognize that sustainability is an issue.

How as ICPI helped to accelerate the acceptance and use of concrete pavers?

I think ICPI has endeavored to be the voice for the industry, and they’ve provided research and technical papers that have advanced the industry. That’s important because we need a third party that’s not biased — it’s not like speaking to a manufacturer and hearing them talk about why their product is superior or necessary. ICPI has provided a format to teach contractors, and has developed programs specifically for residential and commercial markets.

What trends have you seen in the past few years that could contribute to the increased use of concrete pavers in North America?

I think stormwater management is going to be important, because we have the right system for that, and you’re seeing more municipalities making that a priority. I think the growth of our industry will be in that arena. Also, ports will be an area for expansion, like the Panama Canal. We should also see growth in the residential market. All of these are factors that builders and developers need to look at for new opportunities.

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