The Asphalt Jungle

Pavement is subject to all kinds of abuse from nature and humans. But preventing asphalt cracks and potholes has a favorable, money-saving effect.

 People from Minneapolis are surprised to learn there are potholes in Los Angeles. Not surprisingly, people from both Los Angeles and Minneapolis are none too pleased about rough roads.

 This is because – despite common misperceptions about the causes of asphalt deterioration in parts of the country that experience frigid winters – asphalt pavement has many foes of different types. Freeze-thaw cycles in places where temperatures oscillate above and below the 32-degree Fahrenheit mark, sometimes several times in a 24-hour period, are certainly at fault for much of America’s potholes. This is a frustrating fact for commuters, a welcome fact for the commercial asphalt contractor. That is not the end of the story, however.

 Other factors besides cold weather break down the smooth surface of roads and highways, pathways and parking lots. This happens at all latitudes and climatic conditions. The following rouges gallery of pavement busters is what streets and highway maintenance supervisors know all too well:

 Heavy traffic: The effects of heavy vehicles on asphalt roadways is best seen in how the US Congress limits the size of trucks using the Interstate Highway System to 80,000 pounds (20,000 pounds per axel), although that number is higher for several state highways. The reason is damage to asphalt – cracks caused by heavy vehicles permit moisture to enter, which undermines the subsurface.

 Moisture: Moisture ruins much of the built environment. In cold weather, water that gets under the surface layer of pavement expands when frozen, pushing aside the gravel base and upward on the asphalt layer. The cavities created by this eventually collapse from even lighter weight small cars, which is the most common version of a pothole.

 Heat: Moisture under pavement can also cook, leading to steam that literally explodes. During a major heat wave in 2011, portions of roads in Arizona and Texas buckled and blew up due to thermal expansion that came from a month-long string of days where temperatures were above 90 degrees and into triple digits. The fact that black asphalt also holds heat to a much greater degree than light colored surfaces increases this effect. Even without explosions, heat deteriorates the bonds of bitumen holding together the aggregate that makes up the bulk of asphalt.

 Sunlight: In regions blessed with abundant sunshine, UV rays can deteriorate the asphalt surface, permitting more moisture to enter it.

 Chemicals, including petroleum: Aesthetically, such things as motor oil, gasoline and antifreeze leaks from a parked vehicle ruins the appearance of a driveway or parking lot. But such spills also cause the asphalt to break down. Also, sealcoating will not adhere to those spots unless cleaned off before application of the sealcoating.

 Utility work and tree roots: Anything that cuts into or forces the asphalt layer to rise up introduces points of entry for moisture.

 Another reason for asphalt deterioration is shoddy workmanship in installation. This is why your local asphalt contractors’ reputations are very important.

Everyone loves a good deal, and some of life’s best luck is about being in the right place at the right time. But that place is never a driveway.

 If it sounds too good to be true, it probably is.

 More than probably, the guy who knocks on your door and tells you he’s a licensed paving contractor that can give you a new or refurbished asphalt driveway at a steep discount is almost certainly too good to be true. In fact, there’s not a lot of good that is likely to come through this scam disguised as good luck.

 More like heartache and unplanned expenses. There’s a small but persistent “industry” of traveling scammers who go from town to town, as they have for decades, offering cut-rate and shoddy work either at crack sealing or putting a new layer of asphalt over aging driveways. This happens everywhere in the US, Canada and other countries, as it’s a well-established ruse. They sometimes get caught and prosecuted: in 2017, 52 individuals who identify as Irish Travelers in North Augusta, South Carolina were arrested and pled guilty to a variety of, including home improvement scams. According to a report in The State, the daily Columbia SC newspaper, “a popular scam was paving driveways with substandard material,” describing them as “traveling handymen, who roam the Carolinas and Georgia and rip off unsuspecting homeowners by doing shoddy or unfinished repair work after being paid up front in cash.”

 The pitch, often made to elderly homeowners, goes something like this: They knock on the door and say they notice the driveway needs work. This is the homeowner’s “lucky day,” as they were on another job nearby and had excess asphalt leftover from their job. Rather than let it go to waste, they’d repair your driveway that very day at half the normal price. No contracts are involved, the homeowner doesn’t have time to check their credentials, but it looks like a great deal right before their eyes.

 The layer of asphalt laid down might (but won’t always) look ok. Or, they may run out of material before the full driveway is covered, so they explain they’ll be back the following day. But the next day, and the day that follows, and the day after that as well, will come and go with no return of the itinerant asphalt paving crew. What was laid down won’t stand up to much time and traffic – and the homeowner’s money is long gone. With no written contracts, phone calls that go unanswered and no identification of the paving company there is little chance the homeowner will ever be compensated. Chances are the entire driveway will need to be redone by a licensed asphalt paving contractor.

 The Better Business Bureau annually issues statements warning of this scam (almost all asphalt is laid in warmer seasons). They advise that paving companies would almost never have “excess asphalt leftover” from another job, as contractors are very accurate in bringing only the amount of material needed for that day (asphalt has to be laid down within a narrow range of temperatures to set correctly; leftovers would cool and need to be reprocessed at wasteful expense).

 Instead, advises the BBB, the homeowner should always initiate contact with contractors on their terms. Investigate providers, read their online reviews, get more than one quote, and insist on written contracts – with no more than a 1/3 payment up front.

Paving driveways and walkways are commitments to the material for decades to come. Cost differences matter, as do maintenance, longevity and aesthetics.

 The appearance of concrete (typically a light color) and asphalt (it’s called “blacktop” in many regions for a reason) is what distinguishes the two types of paving surfaces – to the casual observer. But there are surprising similarities in composition, and widely divergent characteristics in their cost and maintenance requirements.

 Smart homeowners need to consider the differences. Especially as they set out to find a reputable asphalt paving contractor as opposed to a concrete contractor. They may be the same contractor or they may not. As a rule of thumb, concrete can cost a bit more for installation, it requires less maintenance than asphalt, it can crack (which requires replacement), and it absorbs less heat with a lower tendency to create a heat island effect.

 So it’s a mixed picture. To determine which is best for different applications, it helps first to understand what distinguishes the two. Both are primarily laid on a gravel base, which allows drainage and some flex underneath without altering the surface (important where there are freeze thaw cycles in particular). The key difference, in color and how they work, is that concrete is bound by cement, which is inflexible, while asphalt uses bitumen (derived from petroleum) as an emulsifier. Bitumen can revert to a more fluid state under heat.

 What that translates to largely amounts to maintenance and longevity differences, as follows:

 Maintenance. Asphalt should be resealed 6-12 months after first installation, and then every three to five years later. This not only prolongs the life of the driveway, but it also improves its appearance.

 With concrete, there is no need to reseal it. Concrete may require cleaning if motor oil or other materials stain it. Concrete can also develop cracks, which cannot be repaired while asphalt cracks can be sealed.

 Longevity. In general concrete lasts longer. That said, in colder climates the freeze-thaw cycles can be problematic for both. Potholes form when moisture enters the subsurface of asphalt and then freezes; this is largely preventable with early attention to fissures (cracks) with sealant material. Concrete is laid in slabs, and cracks are for the most part permanent. The “repair” often is a replacement of the damaged slab.

 For a more stylized look, concrete offers many more options. It can be stamped with patterns, or stained, to mimic pavers or otherwise create a broad range of designer effects. Asphalt pavement can also have colored sealants, although those tend more to be used to delineate parking areas or for basketball and tennis court demarcations.

 If the driveway runs along the south or west sides of a house and there is no shade, the homeowner should be aware a darker surface (asphalt) will hold heat longer into the night. That would likely affect air conditioning costs.

Trees provide the shade that pedestrians appreciate as they go for a walk. But when the tree roots push concrete slaps upward a smart solution is needed.

 Is there a better picture of what the word “upheaval” means than when tree roots push a sidewalk slab out of place? And isn’t it amazing how a slow-growing plant can move something that weighs 150 pounds per cubic yard – about 200-300 pounds per concrete slab (depending on sidewalk slab dimensions)?

 What’s not so interesting is the expense and liability risk associated with uneven, heaved sidewalks. A trip-and-fall accident can cost property owners a bundle, depending on who bears that responsibility, even if it is technically on city-owned property. That risk might be equally shared between a municipality and homeowners, but in any scenario a flat sidewalk is preferred for all concerned.

 While a concrete contractor initially laid those sidewalk slabs, they may not be the first person to call with those slabs are displaced by aggressive tree roots. Something has to be done about the roots, work out of the scope of your typical asphalt paving company. Once the roots are dealt with, a good concrete contractor will come much in handy.

 The most common cause of sidewalk slab upheaval is tree roots, which are nature’s way of anchoring the tree, making it resilient to storms, and of course how the tree gathers water and nutrients from the ground. Tree roots can extend up to three times farther from the trunk than the drip line (branches) of the tree itself. The cultivar of tree selected can make this bad or better, and most cities provide some guidance on which will thrive, provide shade, minimize nuisance (dropping seeds and sap), and best withstand storm conditions. Importantly, silviculture research has improved our knowledge about this in recent years.

 But a long legacy of poor choices and inartful placement of problematic trees in the strip between sidewalks and curbs (often called parkways) has created concrete sidewalk slab upheaval in neighborhoods all across America. As municipalities largely decide on the fate of the trees themselves – and the effects of urban heat islands make towns and cities loath to remove mature shade trees – more often that means making do with the tree, tree roots, and heaved sidewalks in a number of ways:

 Call an arborist: An arborist will consider the health of a tree in all respects (tree surgeons largely focus on branches, above the ground). The arborist will look at how tree roots might be cut to enable replacement or repositioning of the concrete sidewalk slabs. It must be noted that root pruning, inground, is usually not a permanent solution – it grows back – and can potentially destabilize the tree and otherwise compromise its health. So the consultation of a professional is strongly advised.

 Excavation of subsoil: Another way to manage around tree roots is to lift the concrete slab (easy, right?) and remove soil below the tree roots. Filling the void with loose clean pea gravel will allow the roots to push down instead of up, enabling the sidewalk to remain flat to grade.

 Create a geogrid: Basically, this involves joining several slabs together to create sufficient force to hold the tree roots down. Employing a metal grid, joining two or more slabs of concrete together (more would be better), the larger slab sits on a gravel bed that provides space for the roots to grow.

Trees provide the shade that pedestrians appreciate as they go for a walk. But when the tree roots push concrete slaps upward a smart solution is needed.

 Is there a better picture of what the word “upheaval” means than when tree roots push a sidewalk slab out of place? And isn’t it amazing how a slow-growing plant can move something that weighs 150 pounds per cubic yard – about 200-300 pounds per concrete slab (depending on sidewalk slab dimensions)?

 What’s not so interesting is the expense and liability risk associated with uneven, heaved sidewalks. A trip-and-fall accident can cost property owners a bundle, depending on who bears that responsibility, even if it is technically on city-owned property. That risk might be equally shared between a municipality and homeowners, but in any scenario a flat sidewalk is preferred for all concerned.

 While a concrete contractor initially laid those sidewalk slabs, they may not be the first person to call with those slabs are displaced by aggressive tree roots. Something has to be done about the roots, work out of the scope of your typical asphalt paving company. Once the roots are dealt with, a good concrete contractor will come much in handy.

 The most common cause of sidewalk slab upheaval is tree roots, which are nature’s way of anchoring the tree, making it resilient to storms, and of course how the tree gathers water and nutrients from the ground. Tree roots can extend up to three times farther from the trunk than the drip line (branches) of the tree itself. The cultivar of tree selected can make this bad or better, and most cities provide some guidance on which will thrive, provide shade, minimize nuisance (dropping seeds and sap), and best withstand storm conditions. Importantly, silviculture research has improved our knowledge about this in recent years.

 But a long legacy of poor choices and inartful placement of problematic trees in the strip between sidewalks and curbs (often called parkways) has created concrete sidewalk slab upheaval in neighborhoods all across America. As municipalities largely decide on the fate of the trees themselves – and the effects of urban heat islands make towns and cities loath to remove mature shade trees – more often that means making do with the tree, tree roots, and heaved sidewalks in a number of ways:

 Call an arborist: An arborist will consider the health of a tree in all respects (tree surgeons largely focus on branches, above the ground). The arborist will look at how tree roots might be cut to enable replacement or repositioning of the concrete sidewalk slabs. It must be noted that root pruning, inground, is usually not a permanent solution – it grows back – and can potentially destabilize the tree and otherwise compromise its health. So the consultation of a professional is strongly advised.

 Excavation of subsoil: Another way to manage around tree roots is to lift the concrete slab (easy, right?) and remove soil below the tree roots. Filling the void with loose clean pea gravel will allow the roots to push down instead of up, enabling the sidewalk to remain flat to grade.

 Create a geogrid: Basically, this involves joining several slabs together to create sufficient force to hold the tree roots down. Employing a metal grid, joining two or more slabs of concrete together (more would be better), the larger slab sits on a gravel bed that provides space for the roots to grow.

Asphalt is largely the same, whether in a parking lot or a driveway. But the construction of pavement differs between the two. Most contractors can do both.

 Reputable asphalt paving contractors with a good history of satisfied customers generally don’t sell themselves as residential-only or commercial-only. This is because the business of building driveways and commercial parking lots is quite similar, therefore most are able to do both. A commercial parking lot contractor can assuredly construct a quality driveway. A residential driveway contractor can build a quality parking lot.

 That is not to say the two projects are interchangeable. They are not. The difference is in depth and drainage design.

 By depth, we refer to the subgrade layer, below what is visible to the eye. Think of it as the supporting structure for the pavement surface. It starts with the natural earth or rock below the midlayer; this is the substrate, which being a factor of nature, varies in thickness. It needs to be free of soft spots, therefore the contractor will evaluate that layer and sometimes compact it by running a full, heavy truck over it or add clay or decomposed granite to firm that area up.

 The physics of this, relative to a commercial versus a residential installation, is pretty straightforward. If the site will receive heavy vehicles, such as delivery trucks to a grocery store, the depth of the subgrade layer has to be thicker. In a commercial setting that will be four to six inches after compaction. For a residential driveway that will largely handle passenger vehicles, all other factors being equal, it would be less than that.

 But the depth of the subgrade is only part of the story. Drainage design is critical in both types of applications, with commercial parking lots being much more complex.

 A driveway will be built to accommodate one, sometimes two, lanes of traffic. As such it rarely will need a drainage system other than to have a sufficient slope for shedding rainwater. The formula for that – assuming that water can drain to both sides – is for the slope to be ¼ inch per linear foot from the crown (center peak) to the edge. For example, if the driveway is 16 feet wide, the crown-to-edge distance is 8 feet, therefore the drop from the center will be 2 inches on both sides.

 Parking lots are generally larger and broader, which means the slope would have to be dramatic to avoid the formation of puddles (standing water tends to infiltrate pavements, which undermines the subgrade and leads to potholes). Instead, water can be channeled into a drainage system built below the surface before paving. Depending on municipal building codes and the extent of the project, a civil engineer may be required to design such a system.

 To be clear, a pavement contractor’s equipment to install residential driveways is the same as what they’ll need for a commercial project.

The fight to get road space for cyclists began with building pavement outside of cities. More recently, designated bike lanes prove to be safest.

 Bicycling is, unfortunately, the source of contentiousness insofar as who gets to use the roads. For some reason, motorists resent human-powered two-wheelers as much as the cyclists are none too pleased with close brush-bys or worse from cars, trucks, and buses.

 This is as true today – even as cities install bike lanes – as it was in the 19th century when bicycles were first invented.

 Over this time, virtually all forms of transportation (horses, bikes, cars, trucks and now scooters) had surprising advocates and adversaries.

 When the first bicycle with pedals was patented, in 1866, pavement was pretty rare. Macadam asphalt, invented in the 1820s, was not widespread, nor was asphalt contractors. Urban areas had their cobblestones and, sometimes, wood block pavers, but bicyclists wanted to go out into the country where rutted mud roads were the best they could expect. No concrete or asphalt was to be found where the best scenery was.

 As it was, bicycles preceded motorcars by several decades. It helped that the first bicycle enthusiasts were well-to-do. So they organized. Local groups formed, pressing for public access in cities (police otherwise forced them off streets), which evolved into a national coalition known as the League of American Wheelmen (LAW). Among its membership at the turn of the century (1900) were John Jacob Astor and John D. Rockefeller.

 This organization exists today under the gender-neutral name, League of American Bicyclists (LAB), and operates with a $2 million budget and 14 staffers. LAB is part of a larger coalition known as PeopleForBikes, which lobbies for bike lanes.

 Going back to bicycling’s origins, a surprising partnership the bicyclists were able to forge in pushing for better roads was with farmers. The agricultural community initially read bicycling as a worthless hobby, a dalliance outside their interests. But when the two-wheel enthusiasts demonstrated that better roads for bikes meant better roads for loaded wagons of hay and corn, the farmers realized that pavement improved their economics: fewer horses were needed and faster transport meant less time required getting to markets. Together, they lobbied Congress to create the Office of Road Inquiry, which ultimately became the Federal Highway Administration.

 Still, the need for dedicated bike lanes was recognized even in the 1890s, when Brooklyn’s (New York City) Ocean Parkway was built, a 5.5-mile bikes-only track that terminated at Coney Island. This led to a “sidepath” movement a few years later, which would have created protected bike lanes on all major streets nationwide; alas funding never materialized for it. By 1908 the affordability of the Ford Model T sank the bike movement for decades. It wasn’t until 1967 that Davis, California installed what was America’s first painted bike lanes, copying what was more commonplace in Europe.

 In 1968, the Vienna Convention on Road Traffic recognized bicycles as vehicles, a definition that led to much more global acceptance of bikes and bike infrastructure. By 1999, the American Association of State Highway and Transportation Officials (AASHTO) issued its first guidelines for creating bike-friendly streets. Six years later, researchers at the University of Texas/Austin identified how painting bike lanes on streets ensures greater safety; a few years later, research in Montreal identified that protected bike lanes (with physical separations from car lanes) reduce the risk of injury even further. By that time New York City was systematically installing protected bike lanes. When an entire lane in Brooklyn was removed from car usage and dedicated to bicycles, weekday bike commuting tripled.

 According to the PeopleForBikes website, the most recent figures reflect 550 miles of protected bike lanes in 124 cities in the US. While there are many more miles of painted bike lanes, which lack barriers and bollards for protection, the protected lanes are found to significantly increase safety and, as a result, overall use.

A driveway project might seem like buying a commodity, i.e., one paver is the same as the next. But often a lower price means lower quality – and higher risk.

 If your house needs a new driveway, you find an asphalt paving company and they just do it, right? I mean, every house has a driveway. Everyone just pays the driveway contractor. This isn’t complicated.

 Or is it? There are driveways that turn out badly. Generally speaking, there can be poorly installed driveways that rut (get depressions), have cracks and potholes, or sometimes don’t hold up to seismic events or shifts in the subsoil.

 What is not apparent in looking at the driveways of home upon home upon home are the liability costs that sometimes happen with asphalt or concrete driveways. Heck, even a beautiful paver drive-up can be riddled with lawsuits.

 The reason any driveway ends up being problematic – i.e., an expensive headache – is when the workmanship is poor or the crews doing the actual work are inadequately trained and protected. From a safety standpoint, poorly -trained or -managed work crews might have serious accidents when handling hot asphalt or heavy concrete. Believe it or not, those accidents might cost you, the customer, a lot of money.

 The reasons subcontractors are sometimes used in paving projects are when the homeowner is actually engaged in a larger landscaping or building project, where the primary provider is a landscape architect or a builder. You hire them, and they hire various subs where their expertise isn’t right for the job. Or, the nature of the job – on a hilly site perhaps – requires a little more engineering than is typical. That might involve soils experts and other civil engineering work, and they might have preferred suppliers for such projects.

 Where subcontracting gets unnecessarily risky is when the “contractor” cuts corners on the types of labor used to do the work. They would do this to reduce their labor costs – which might make them the lowest bidder, should you approach this by getting competitive bids – because the contractor doesn’t cover health insurance, payroll taxes, or, most importantly, accident compensation insurance. Even worse, that corner cutting might mean the contractor lacks liability insurance.

 In the case of a failed end product, or an injury-causing accident, there actually is a risk to the homeowner. Obviously, a bad paving job might require a re-do, which may or may not be an expense borne by the homeowner. In an accident, the project might go on a pause, before being completed, in part because the contractor then needs to recruit new workers for the project. If the injured worker decides to sue the employer for injury compensation, which the employer has no insurance against, it’s in the realm of possibility that a sharp legal team will also seek damaged from the owner of the site where the accident occurred.

The urgent need to reduce urban heat is fortunately driving innovation and experimentation. Los Angeles is expanding its CoolSeal program in 2019.

 The term “urban heat island” may have entered the general lexicon in the summer of 1995, when as many as 800 people died in a slow-moving heat wave disaster in Chicago. Temperatures in the Windy City hit triple digits (Fahrenheit) for five days, and the city’s concrete buildings and asphalt roads and highways held the heat into the night. For vulnerable populations, the elderly in particular, that meant no respite with nighttime cooling.

 The cause of heat islands is basic physics: Dense objects like pavement capture and hold heat. Even more so if the pavement is dark, as is most asphalt, because the darker the color the more ultraviolet rays it absorbs from the sun. Pavement surfaces can be between 68 and 86 degrees F higher than the surrounding air temperatures on sunny days in summer – at times as high as 150 degrees F, truly hot enough to fry an egg.

 The good news is the commercial asphalt paving industry has devised solutions to cool areas around streets and parking lots. The trick is to reflect those ultraviolet (UV) rays off the pavement, creating something called the albedo effect. For example, a recent layer of fresh white snow in sunshine reflects a lot of UV, meaning it has a high albedo. A roof covered in black bituminous material (as most were until recently) absorbs UV rays, making it a much hotter surface because it has low albedo.

 One such pavement solution is the CoolSeal coating project underway in Los Angeles. It involves applying a titanium dioxide-infused liquid seal coating to existing streets. Laid down as a ¼ millimeter layer, the temperatures on CoolSeal streets is about 10-20 degrees F lower than a traditional (black) asphalt street.  Commercial paving contractors have been out in force throughout summer.

 Begun in 2014 in LA as an experiment, the program has been expanded from single blocks to several blocks at a time and will cover 1500 city blocks over the next decade.

 CoolSeal offers other benefits as well. It requires less energy to light at night, at the same time when use of air conditioning can be reduced with lower nighttime temperatures. And given how high temperatures cause asphalt deterioration, reducing those temperatures should prolong pavement life.

 There may be downsides to CoolSeal in that the reflected light, similar to what downhill skiers and Arctic explorers find, can be bright enough to require sunglasses. And while pets show a propensity to walk on CoolSeal-coated streets – bare paws prefer it – the reflected light can cause the ambient air to be warmer during the daytime. The biggest benefit is the pavement retains less heat, literally at the end of the day, enabling cooler nights.

The majority of outdoor court sports playing surfaces and running tracks are made with asphalt. It’s under a layer of acrylic, usually, and built to last.

 The clay courts at the French Open might get all the buzz, but two things should be clear about the vaunted venues of the tennis Grand Slam: they are not made of the type of clay that gardeners know and hate (they’re made of crushed shale, stone, or brick). Also, other Grand Slam courts are made of other materials.

 And to be clear, the reigning kings and queens of tennis are all over the board on what type of surface they prefer: clay (Serena Williams, Rafael Nadal, Andy Murray), grass (Roger Federer, Venus Williams, Johanna Konta), and hard court (Novak Djokovic).

 But in fact the tennis courts that most of us amateurs play on are asphalt-based hard courts – about 95% of them. They may not look like the black asphalt we use to pave driveways and highways, and they should be built by different methodologies. But the part that is most visible, and which affects play, is generally covered with an acrylic surface layer, typically with green pigment. Of note, while perceived as somewhat pedestrian, hard courts are nonetheless used at the US Open (Forest Hills, NY) and the Australian Open (Melbourne). The play of the tennis ball on hard courts is faster than, for example, grass (Wimbledon uses perennial ryegrass); this is because grass absorbs much of the ball’s energy.

 But to the point of building tennis courts, outdoor basketball courts and running tracks, all usually have an underlayment of asphalt. The construction of each has to be done to the standards of the sport, not just in dimensions but in factors that relate to athletic performance. Also, because many of these facilities are publicly owned by parks departments and public schools, they need to perform with as little maintenance expenses as possible.

 This is not a service the average asphalt paving company provides. Sports court construction is a specialized service few asphalt installers are equipped to deliver. When seeking a contractor to design and construct a sports court, find one with a proven record of expertise.

 In all cases, the added expense of the acrylic surface over asphalt puts pressure on the contractor to achieve precise planarity (the plane as required by the sport and to achieve rain runoff) and smoothness. This is primarily done with two layers of asphalt – the second corrects for the flaws of the first – over an aggregate (decomposed granite) base. A clay or rock base under that is preferred. When a contractor has to cut into organic (softer) soil to build a tennis court, for example, the earth needs to be compacted first lest there be settling of the court a year or two after installation.

 There are specific instructions on how to build tennis, track and basketball courts outside, provided by the American Sports Builders Association. The organization closely tracks development of current and accurate technical information in pursuit of maximum standards of design, construction and maintenance of sports venues.

When public sidewalks lift or drop, creating pedestrian hazards, the responsibility for damage repairs often falls on homeowners.

 The importance of functioning sidewalks is often overlooked. But given the importance sidewalks give to communities – to the health of citizens, access for the disabled, and even assists to commerce – to forget to budget for sidewalk construction, maintenance and repair is folly.

 Just as important to individual homeowners, the financial burden for repairs very often falls upon them.

 But first, why are sidewalks important? None other than the original urbanist, Jane Jacobs (“The Death and Life of Great American Cities,” 1961 and subsequent reissues), spoke of the contributions sidewalks make to our cities. “Sidewalk width is invariably sacrificed for vehicular width, partly because city sidewalks are conventionally considered to be purely space for pedestrian travel and access,” she wrote. “ [Sidewalks] go unrecognized and unrespected as the uniquely vital and irreplaceable organs of city safety, public life, and childrearing that they are.” Her treatise speaks to the health of urban environments with functioning sidewalks, even claiming that crime (down) and social discourse (up) are impacted by functioning sidewalks.

 But still, even in neighborhoods where sidewalks are valued, things can go awry.  Not all commercial and residential asphalt contractors are created equal and even the best asphalt paving company can make mistakes. Improper installation on looser soil can lead to sinking slabs of concrete. Or excessive water on and under pavement – think leaky pipes, or a redirected downspout – can undermine the sidewalk. In some cases, with certain species of trees, roots can also lift sidewalks.

 The result of shifting and lifting sidewalks is that it can be difficult for people in wheelchairs or with other walking disabilities to traverse these areas. Children on bikes (under age ten bicycle riding is allowed on sidewalks), and parents with baby strollers, encounter difficulties and might have accidents. Runners whose feet might catch on uneven pavement can take hard and injurious falls.

 Depending on the municipality, the responsibility for maintaining a safe, flat sidewalk can fall partially if not completely on the owner of the adjacent property. A publication from the League of California Cities, “But it’s Your Sidewalk! Sidewalk Repair and Liability” (2014) clarifies provisions of the Golden State’s Streets and Highways Codes section 5610, which largely places the costs on the homeowner. Elsewhere in the US those costs are often shared between the municipality and the private property owner.

 An exception to this burden being on homeowners is when a city-owned tree, placed in the public right of way, has a root system that raises the concrete slab. Most often, the city then is responsible for repairs.

 Importantly, whomever is responsible for the repairs and maintenance of the sidewalks also bears liability if and when someone is injured by the disrepair. The average cost for a trip-and-fall accident is $30,000, and can go much higher.

Tripping and falling on public, commercial or private property is all the same: injuries can happen and they can be a costly liability for the owner.

 It is equally vital that homeowners and commercial property owners hire the best asphalt contractor to build and maintain their driveways, sidewalks, walkways, pool decks and parking lots.  Reputable residential, as well as commercial asphalt construction companies assure that surfaces are durable and even, with an eye on safety and liability for the property owner.

 Want to know what kinds of risks you run with uneven walkways on your property? Just google “slip and fall injuries” and the first page of search results will likely be a list of law firms who specialize in personal injuries from falls.

 Note that the responsibility for safe, fall-free walkways isn’t just a concern to commercial enterprises. A homeowner or owner of apartment or condo units is subject to litigation as well from poorly installed or maintained hardscape (asphalt pavement, cement, paving stones) on property. The facts are that disability, pain and property loss due to poorly maintained pavement, lighting or other hazards fall on the property owner, be it private or commercial.

 The injured parties are more than just members of a household or close friends. Delivery personnel, people attending parties, even relatives making a visit who trip in a driveway pothole, uneven sidewalks, loose rugs or icy spots due to a drip from a gutter, all can suffer injuries and eventually engage in a lawsuit (yes, even relatives sue other relatives sometimes).

 How serious can a trip-and-fall injury be? Some facts:

  Bones break     in about five percent of slips, trips and falls.

Older people     are particularly vulnerable, as about one-third of people over the age of     65 fall about once a year.

Being younger     is no protection. For people over the age of 24, the most common causes of     non-fatal injuries are trips and falls.

Traumatic     brain injuries from falls are greater than those from organized sports.

Almost all     (95 percent) of hip fractures are due to trips and falls.

The average     cost of a slip and fall injury is $30,000, and those caused by icy     surfaces average as high as $48,000 (costs vary by locale; stats from the     U.S. Centers for Disease Control and Prevention)

In most     cases, a homeowner’s property insurance will cover losses related to the     accident – to a point. The homeowner might have medical payment coverage     in addition to liability coverage.

Medical     payment coverage might be limited to $5000; beyond that it’s on the     homeowner.

Liability     coverage applies only if there is evidence of negligence on the part of     the property owner.

 This last point is critical, as negligence is largely in the control of the property owner. A flat, smooth-but-not-slippery walking surface is what one needs to provide guests.

 That starts with removing trip-and-fall causes, such as loose, random objects (hoses and wires, for example) in walkways, and ensuring flat paved surfaces on driveways and on sidewalks. It’s also important to study where rain puddles and perhaps freezes or grows slippery moss, which can be a function of settling or an unintentional water source (e.g., roof gutters that leak).

The added expense of the surface material used around a pool should be regarded as a barrier to problems – not the least of which are slip-and-fall accidents.

 A pool in a backyard is what defines a dream home for many. Particularly in warm climate markets, the pool can be a must-have for homebuyers.

 But just as important as the pool is the area surrounding it. The hardscape surface material matters, aesthetically, in framing the pool and providing jumping-off points. The use of brick pavers, concrete, flagstones or wood decking provides a place for water to splash without muddying turf grass areas.

 And that decorative hardscaping allows a place where occupants can enjoy soaking up sunshine. But safety is also a critical component of that hardscape.

 In-ground pools – despite their image of luxury, providing halcyon summer days and elegant nights – are also associated with horrible accidents. The National Safety Council reports that in ten states (Alaska, Arizona, California, Florida, Hawaii, Montana, Nevada, Oregon, Utah and Washington) drowning is the number one cause of death to children under the age of 14.

 In many cases, those deaths aren’t just from going underwater due to a lack of swimming skills. Some are also related to slip-and-fall accidents, where a child or an adult lost their footing or balance on the surrounding hardscape. An even surface is rarely the problem, but a slippery surface is. Consider how children naturally run while playing near a pool. Teenagers might “hot dog” it by running into a cannonball jump. And adults, with or without a cool cocktail in hand, can be playful around the water’s edge. If the area nearest the pool is slippery and the adult or child loses his or her footing and hits their head, injury or death can result – sometimes from drowning, sometimes from just the traumatic brain injury.

 Pavers are generally considered the safest of materials to prevent tragic accidents. Yes, the very same pavers – or “paving stones” that an asphalt contractor utilizes on fancy estate driveways. This becomes even more so with the application of a matte sealant, which adds traction to the paver surface.

 Surprisingly, these sealants used on pavers give surfaces a shinier luster. It is a safety feature that, surprisingly, also adds a certain elegance. Just as important, the treatment will preserve the pavers against the elements (rain, ultraviolet rays, freezing, etc.) longer than if left untreated.

 Another advantage of pavers is that they are set in sand and thus flexible to seasonal temperature shifts and small seismic events. With a solid sheet of concrete large cracks develop that are both unsightly and can add a different kind of hazard, the trip-and-fall effect.

It may be a little jarring to drive on a stretch of road that’s been scraped. But milling is the cost-cutting, environmentally friendly way to improve pavement.

 An environmentally meaningful innovation came out of the oil shocks of the 1970s that is often overlooked. It is asphalt milling, also referred to as cold planing, pavement milling and profiling. It’s a pavement improvement technique used asphalt paving contractors when the surface of aging asphalt pavement is scraped off, which later is overlaid with new asphalt that is partially composed of what was scraped.

 So what does this have to do with the 1970s? A 1973-74 steep uptick in oil prices happened coincidentally with an eco-consciousness of that era (asphalt milling technology goes back to the earlier parts of the 20th century, but went largely unused for decades). When the cost of asphalt binder, which is almost entirely based in petroleum and its byproducts, increased by nearly 400% from a supply-limiting decision of the Organization of Arab Petroleum Exporting Countries (OAPEC), the asphalt pavement industry began to seriously consider recycling existing pavement to counter the cost burden. Note this was just a few years after the first Earth Day in 1970, a symbol the modern environmental movement.

 It was wildly successful and widely adopted by contractors who specialize in asphalt repair as well as new asphalt paving. Today, reclaimed asphalt pavement (RAP) is one of the most recycled materials in America. According to the US Environmental Protection Agency and the Federal Highway Administration, about 80 million tons of asphalt material is reclaimed through pavement milling every year, and of that almost 100 percent is recycled for reuse again on roads, streets and highways. Compare that to recycling rates for aluminum cans (60%), newsprint (56%), soft plastic drinking bottles (37%), glass beverage bottles (31%) and magazines (23%).

 By reducing demand for oil-based binder and aggregate, American taxpayers save about $2.5 billion dollars on public highways while none of that material is hauled to and deposited into landfills.

 The process of milling involves, with some variation, carbide cutters and large rotating drums that remove and grind the road surface. The removed material is then channeled onto a conveyor belt that is part of the milling vehicle. Heat generated by the process and the resultant dust are managed with a constant spray of water. Lasers or string-lines are used to achieve the milled depth of the existing pavement.

 The intermediate result is the scraped street with which all motorists and bicyclists are familiar. The end result is the addition of a new “lift” (top layer) of smooth asphalt, much of it composed of recycled material that has been reprocessed at an asphalt plant. According to a 2011 study conducted for the US Department of Transportation/Federal Highway Administration (“Reclaimed Asphalt Pavement in Asphalt Mixtures State of the Practice”), mixtures containing up to 30% RAP in newly laid asphalt perform as well as pavement made entirely of virgin material.

How much repair is required is of course a function of pavement’s current state of degradation. There are many options to restore a smoother surface.

 Asphalt, like people, deteriorates over time. It may be a tough mix of gravel, sand, and bituminous fluid that stands up to semi-tractor trailers, but time and other factors take their toll. This is why we have potholes – and the imperative to repair asphalt on a regular basis. Asphalt repair service is a brisk business nationwide.

 Indeed, regular maintenance is the key to longer last roads, parking lots and driveways. Money spent earlier saves much more money later.

 Private and commercial asphalt contractors provide repair services, but what exactly is included in pavement repairs? What should the homeowner or department of transportation do to stave off cracks, crevices and the need to curse from pothole hits to vehicles? There are several tactics, somewhat dependent on the current degree of asphalt damage or deterioration:

 Regular maintenance

 1.  Seal surfacing: This is where a slurry is applied to the driveway or parking lot to fill cracks and voids, extending the life of the pavement that was laid a year or longer ago. It effectively protects from water seepage below the surface, which undermines the pavement and is the primary cause of potholes.

 2.  Crack sealing: Instead of sealing an entire road, parking lot or driveway, noticeable cracks can be sealed on a spot basis (through the entire length of the crack) to prevent water infiltration.

 3.  Resurface: Older pavement might simply be ready for resurfacing if there are no serious problems. It can be resurfaced with 1.5 inches or more of asphalt material laid over the existing pavement.

 Light damage repair

 4.  Throw-and-go patch material: When the season is wet and/or cold (below freezing), it may be necessary to do a temporary repair of loose asphalt that is tamped into the hole. It is not likely to last, as asphalt will not adhere to the hole surface areas.

 5.  Permanent patching: When weather conditions allow (usually, drier and warmer temperatures above 50 degrees F), a pothole up to 4 inches in depth can be repaired with permanent asphalt mix.

 Severe damage repair

 6.  Skin patching: When pavement has depressions (look for pooling after rainfall) or potholes, a skin patch might applied to restore level pavement.

 7.  Removal and replacement: When the problems are significant and widespread, a scrape-and-replace is advised. This not only provides longer-lasting pavement, the material that is scraped is 100% recyclable.

The quest for travel is old as time. But it took millennia until McAdam devised asphalt pavement – an invention largely driven by the vehicles that needed it.

 Nobody is sure who the first asphalt contractor was but we do know this: The first asphalt street in America was in front of the Newark, New Jersey city hall, laid in 1870. The mixture of sand and the tarry substance known as asphalt (bitumen) had previously been used for sidewalks. Note this was at a time when mass-produced bicycle transport was coming into vogue, prior to the development of horseless carriages (cars). It was the bicycle clubs that initially pressed for smooth pavement.

 Shortly thereafter, Pennsylvania Avenue in Washington DC got its first pavement of asphalt. The road building industry was rather clever about impressing the Powers That Be on the benefits and virtues of solid surfaces.

 But the origins of pavement and ensuring contiguous travel go back much further in history. Herewith is an abbreviated chronology of road building – and why today more than 90 percent of streets and highways are made with the asphalt “macadam”-style pavement:

 2350 B.C.: A cuneiform tablet from the Akkadian Empire (Arabian Peninsula) includes directions on using bitumen, the tarry substance later used in road building that then was used as a water seal on baths and cisterns.

 2000 B.C: The Silk Road connected Asia and the Middle East, and later (13th century A.D.) provided Marco Polo a means to find China and bring gunpowder and paper (but not spaghetti, per popular legend) to Italy. That early version of a highway had a big problem: Use caused ruts, and rain caused puddles and washouts.

 312 B.C.: The Romans completed the Appian Way, which involved small stones in mortar laid on top of dirt, topped with tightly interlocked stones that were cambered along the spine of the road (slight elevation along the middle to promote runoff), with ditches on the side to channel storm water away. Portions of the road were a mix of iron waste and gravel, which oxidized and fused from rain, forming an interlocking surface. The water and erosion problem was solved? Not quite. The success of those roads taking traffic was dependent on bedrock below; a soil subsurface usually meant a rougher stretch of the Way.

 19th Century: Since the Romans all kinds of efforts to ensure smooth pavement were tried. But bicyclists needed flat surfaces, and soon thereafter the cars did even more so.  This created the drive for John McAdam to apply his engineering skills to dependable road building.

 The problem was then and remained (even today) water and deterioration ­– for travelers on the Silk Road and Appian Way and bicyclists in Newark and Washington DC and Chicago and Los Angeles.  But McAdam had a plan.

 Rather than depend on a solid bedrock foundation, which isn’t available everywhere, and from experiencing the shortcomings of brick and wood plank streets (part of why Chicago burned to the ground in 1871), McAdam theorized that a solid upper crust (asphalt pavement) placed over gravel could be sustained over soil instead of bedrock.

 McAdam was correct – so much so the “Macadam” road building style was pretty much the template for what has been built ever since. That style includes a middle layer of angular rocks (not round pebbles) that when compressed form a lock. The upper layer also uses angular (but to a lesser degree) rocks mixed with bitumen (asphalt), and sand. Importantly, compaction of the water-resistant upper layer is done so that cambering along the center of the road allows rain runoff.

 20th century: The success of Henry Ford’s affordable Model T cars were the impetus for applying the macadam method to roads in the first half of the century, with even greater needs following World War II. National security concerns drove the interstate highway system – a boon to seeing the USA in your Chevrolet, but also to allow movement of vehicles from coast to coast as needed. Every fifth mile of the Interstate System is straight, allowing it to be used as an airplane landing strip.

 Some roads are built of concrete but not many (about 4%; 96% are asphalt). Concrete costs more, is inflexible to utility work under streets, takes more time to construct and is noisier to build. By some estimation, asphalt is the “greener” material, involving fewer greenhouse gases in its production than with concrete. This is subject to some debate because different circumstances such as location yield different comparisons; also, concrete is often a subsurface to asphalt, particularly in superhighway construction to increase resiliency to heavy traffic.

 Importantly, both asphalt and concrete are routinely recycled. And just as important: a smooth road enables smoother driving and more efficient fuel usage.

Persistent greasy stains – from cars, birds and trees, mostly – can ruin the appearance of an entire property. There are several ways to clean it.

 Just as no man is an island, no driveway is one either. A home’s concrete driveway in particular can add great value to the home it services. But maintaining that driveway, keeping it clean from oil and tree and bird dropping stains, is essential for making sure it adds value instead of detracting from it.

 As any realtor can tell you, driveways are important to the look – and value – of a home. A concrete driveway contractor also knows this, as well as asphalt paving contractors.  They’re busy six days a week designing, constructing and repairing driveways.

 That said, certain cleaning methods can be overzealous and harmful to surrounding landscaping as well as the person working with it. So we’ll break down the methods and materials used for washing a concrete driveway with particular attention to (a) what works at cleaning and (b) its potential harmful effects on plants and wildlife, plus ways of mitigating the harm.

 But first it helps to understand what you’re up against. Start with color: concrete is somewhere between grey and white, so it’s less forgiving of stains than asphalt. So whether it’s motor oil or crushed elderberries or berry-eating bird droppings from a tree, dark stains are more evident on concrete. Also, the surface of concrete driveways is generally porous, so other liquids absorb and stick to it. Your work is cut out for you if your car has an oil pan leak.

 Here are ways to go about cleaning the concrete driveway surface, with due warnings on what might go wrong.

 Soap and scrub: A quick, if not exhausting, method is good old dish soap and water with a good scrub brush. Even if it doesn’t fully remove a stain it can reduce your need for other methods. Where there is a slope and several stains (and all driveways should have some slope to shed rainwater), start at the top so that the soapy water runs down to where you’re cleaning next.

 Power wash: Why do the hard scrubbing when water pressure can do it for you? Use the fan tip washer nozzle – best a 25-degree fan or 15-degree nozzle for particularly stubborn stains – to dig into the stain. A tighter fan might damage the concrete, and take care not to aim the wash at other people or pets, as it could cause injury. Also, as with soap and scrub, start at the top of the driveway and work your way down.

 Degreasing cleaner: If a persistent stain needs a little something stronger than dish detergent, kick it up a notch with trisodium phosphate (TSP). This is a degreaser used by professionals for tough, oily stains. In a mix of 1:30 (about one cup to a gallon of water), apply it to the stained area and allow it to sit for 20 minutes, then scrub and rinse with a garden hose. For particularly egregious stains, add grit by including cornstarch or diatomaceous earth to the TSP to create a paste.

 TSP can damage the skin and eyes, so wear protective gloves and eyewear. TSP can also be used to kill harmful fungus and bacteria in gardens and indoors. But be considerate of nearby natural ponds and lakes where the high alkalinity can lead to algae growth. A small amount shouldn’t upend a local pond’s ecosystem, but frequent and heavy use might.

 Chlorine bleach: Just as with sheets and nice dress shirts, chlorine bleach can brighten the white color of a concrete driveway in addition to helping clean it. Mix it in a 1:1 ratio with water, then scrub it into the stain. But just as it can hurt the eyes and other sensitive areas, it can be deadly to plants where the water washes off the driveway. In tightly packed neighborhoods where lot lines coincide with the side of a driveway, it often happens that the neighbors plants are killed – which no one wants to happen. Proceed with caution and courtesy.