For owners and stakeholders funding a project, the idea of a concrete boardwalk may have never crossed their minds. While well known to many landscape architects and contractors, constructing a boardwalk out of precast concrete can raise some questions for those who are new to the subject.
At PermaTrak, we aim to demystify the concept, educate our clients, and help demonstrate the tremendous life-cycle value of our product. Our resource library contains information centered around questions we receive and current industry trends.
This topic came up recently on our new video series, Ask a Boardwalk Engineer, where PermaTrak's Director of Engineering Andrew Craig sat down with host John Pyle to walk through these exact misconceptions. Watch the full conversation below, or keep reading for the full breakdown.
Misconception #1: Concrete is more expensive than wood or composite materials.
It is true that wood tends to be less costly at the onset when compared to concrete, though the cost of lumber has increased dramatically in recent years. However, the startup costs are only part of the overall picture. It is important to consider the costs of lifelong maintenance associated with a project.
One PermaTrak client compared costs on a smaller boardwalk and found the concrete option ran about 30% higher on day one. By year 20, though, the timber option had cost twice as much once replacement and maintenance were factored in.
Since the structural strength of concrete is superior to wood, the wider (greater than 10 ft. clear) and more heavily loaded boardwalks (emergency vehicles and specific county maintenance vehicles) have proven concrete to be cost competitive with wood. This superior strength allows standard concrete beams (stringers) to span greater distances than wood, around 20 ft. for concrete compared to roughly 10 ft. for typical timber designs, cutting the number of foundations roughly in half and saving on foundation costs. Concrete boardwalks also typically use just two beams regardless of width, while timber requires additional joists as the boardwalk gets wider.
Additionally, wooden boardwalks require considerable maintenance that incurs additional expense, including the replacement of warped and rotten boards and even full replacement in a timeframe of 10 to 15 years.
While precast concrete is usually a higher upfront cost, it requires no maintenance and can last upwards of 50 to 75 years, per Army Corps of Engineers.
Check out our article “Life Cycle Maintenance Costs” to learn more about the cost of concrete versus wood and composite materials.
Misconception #2: Concrete only works in certain environments and damages the ones it's installed in.
Concrete is often assumed to be a rigid material that only suits certain sites, and some believe installing it can even harm the surrounding environment. Neither is accurate.
Concrete is highly versatile, making it a prime choice for a wide range of environments and climates. Concrete boardwalks are installed using an optimal foundational system for each project's unique geographical factors, like soil characteristics, lateral load, and uplift. On a project in Lake Tahoe, for example, PermaTrak boardwalks were designed for snow loads of 200 to 300 lbs. per square foot, two to three times a typical boardwalk's demand, simply by adjusting the rebar and concrete mix strength rather than changing the piece sizes.
The same flexibility applies to harsher climates more broadly. For coastal applications with heavy saltwater exposure, or projects in very cold climates, PermaTrak can adjust the concrete mix design with air entrainment and admixtures, and use epoxy-coated or chromium-infused rebar for added corrosion resistance. This ability to match the foundational system and mix design to a project's surrounding conditions makes concrete a viable solution for stable environments as well as more sensitive ones like wetlands. Unlike other materials, concrete also withstands extreme hot and cold temperatures. It does not crack in dry climates or warp in wet climates, is impervious to termites, and is unaffected by other harsh conditions like saltwater and bushfires.
Precast concrete's effect on the environment is minimal, especially when compared to that of lumber. Lumber is often treated with chemicals and preservatives that, over time, damage the natural environment by leaching into the surrounding land, soil, and water, a particular concern in wetland environments with low flow rates, where copper-based treatment chemicals can begin leaching out even in the early phases of a boardwalk's life. Precast concrete, on the other hand, is an inert building material that has not been chemically treated or altered, meaning its use does not contribute any toxins into the area around it.
Concrete boardwalks can also be installed via top-down construction, which minimizes disturbance to the surrounding environment. Because it is composed of only natural raw materials like sand, water and stones, the materials used in a concrete boardwalk can be repurposed in other precast concrete projects if the boardwalk is ever removed in the future.
An added benefit of the modular design of a precast concrete boardwalk is that it allows for the structure to be fully disassembled and relocated in the future.
Misconception #3: Concrete is a high-maintenance material.
The only potential maintenance needed for precast concrete boardwalks is an occasional power wash to remove any buildup of dirt, dust, or algae. No additional treatments or chemical additives are necessary to ensure longevity.
While wood will ultimately decay, rot, and warp, especially if not repeatedly treated with chemicals, precast concrete maintains its integrity for upwards of 50 to 75 years (compared to an estimated 3 to 5 for unmaintained and 12 to 15 for heavily maintained wooden structures).
For more information, check out our article, “What Kind of Maintenance is Required for a Concrete Boardwalk?”
Source: Putnam Greenway, NYC Parks Twitter Feed
Misconception #4: Construction of concrete boardwalks can easily damage tree roots and other natural factors, leading to a shorter life span.
While poured (cast-in-place) concrete is susceptible to damage from tree roots and shifting conditions, precast elevated boardwalks offer a solution.
Depending on the site, PermaTrak's engineers take one of two approaches: locating slender, deep foundation elements like helical piers in the gaps between existing root zones and below the shallow root structure, or, for larger or more sensitive trees, or areas with a dense concentration of roots, using precast pedestal footings that are cast in the plant and simply set on top of the sensitive root zone with no excavation required at all.
The foundations for our precast concrete boardwalks, like the modular PermaTrak Low Profile Series, for example, can be positioned to avoid the root systems of nearby trees entirely.
One such application in Washington state allowed a community to preserve mature trees and effectively reach its environmental goals.
An elevated concrete boardwalk under construction in Shoreline, WA
Similarly, the Putnam Greenway in New York City's Van Cortlandt Park was uniquely developed, allowing a trail to fit comfortably into the natural setting with minimal disturbance to the surrounding ecological environment.
As a precast modular system, PermaTrak's products also flex as the ground moves, shifts, or settles over time. Joints are dispersed throughout the construction, which allow the entire walkway to sink, heave, and otherwise move with the earth, root systems and all, thus eliminating the potential for cracks and separations in the boardwalk surface.
Misconception #5: Concrete can't handle curves or radius geometries.
Concrete is highly versatile, making it a prime choice for a wide range of environments and climates. Concrete boardwalks are installed using an optimal foundational system for each project's unique geographical factors, like soil characteristics, lateral load, and uplift.
The ability to match the foundational system to the project's surrounding area makes concrete a viable solution for stable environments as well as more sensitive environments like wetlands.
Unlike other materials, concrete also withstands extreme hot and cold temperatures. It does not crack in dry climates or warp in wet climates, is impervious to termites, and is unaffected by other harsh conditions like saltwater and bushfires.
Misconception #6: Anyone in the business can produce precast boardwalks.
The quality and appearance of a finished project is largely dependent on the expertise of the professionals involved. It's critical to thoroughly evaluate precasters before partnering on the construction of a concrete boardwalk system.
PermaTrak has spent 16 years focused exclusively on precast concrete boardwalks, with more than 700 structures installed across North America. That focus matters. It's a system with a lot of engineering, planning, and design detail behind it, from integral color and texture options to matching span arrangements and widths to a project's specific needs, that goes well beyond simply producing concrete components.
PermaTrak works with landscape architects and engineers to design boardwalks that will accommodate specific environmental factors while delivering the aesthetic features our customers desire. We also thoroughly vet and partner only with specific precasters across the nation to develop boardwalks of the highest quality.
For the best product and overall experience, contact us for a no-obligation consultation.
Helping to Educate Stakeholders
We hope these answers, and the conversation in the video above, help clarify any misconceptions you may have about concrete boardwalks. Feel free to share with others as well, particularly if you've gotten one of these questions while working on a project.
Have you heard any other misconceptions about concrete boardwalks that you'd like us to address? Drop a comment on the video or reach out. We'd love to cover it in a future episode or add it to our resource library.
