U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
The following sub-section summarizes the common repair practices associated with concrete sidewalks based on the research conducted for the report and the discussions conducted with communities as presented as part of Chapter One. The Guide will elaborate upon these identified repairs and expand the discussion to asphalt pavement and brick and concrete paver. While this research report identified the current state of practice for sidewalks, the Guide itself will provide a series of exemplary approaches to maintenance repair practices accompanied with recommendations.
Maintenance practices can be categorized into two main groups: short term measures typically lasting from one to five years, and longer term measures lasting many years, perhaps in some situations even over ten years. Short term measures consist of repairs that are often temporary until sidewalk segments are replaced. Long term measures include sidewalks being replaced either through a sidewalk replacement program or when a street is reconstructed and sidewalks are replaced as well.
When a sidewalk is reported as damaged, or damage is found during routine inspection, temporary repairs may be made. These temporary measures may include wedging or patching with asphalt or quick-mix cement that may not meet a municipality's desired level of maintenance. However, the temporary repair should alleviate most hazard concerns until a more comprehensive repair is later performed.
There are several measures that can be considered short term maintenance techniques (lasting one to five years) for sidewalks and trails. The main measures include wedging, patching, horizontal cutting, grinding, mud-jacking, overlays, etc. and the inevitable solution in many cases – sidewalk replacement – which is most often considered a long term solution.
The universally accepted long term maintenance technique is sidewalk replacement. However, many of the communities contacted have had some success with grinding and mud-jacking as longer term solutions. Horizontal cutting is a newer technique that is similar to grinding and should have the same success rate as grinding. The problem in considering grinding, mud-jacking and horizontal cutting as longer term solutions is the uncertainty that the underlying problems associated with these fixes will continue to be an issue. For example, if a sidewalk sags and mud-jacking is used to correct the problem, the sidewalk may continue to sag after the mud-jacking due to the underlying problem – an unstable base. Likewise, grinding and horizontal cutting will often be used to rid a sidewalk of a tripping hazard, but will leave one or two sidewalk panels with a cross slope of greater than two % or with warped transitions between panels.
Following are photographs and descriptions of the main set of sidewalk repairs and replacement.
Entails the placement of an asphalt or concrete filler placed in the advance of a vaulted section of a sidewalk or shared use path to essentially provide a ramp and remove a tripping hazard. If done properly to a sidewalk that has not vaulted severly, it can be made ADA accessible. The wedge on the left is just a few days old, while the wedge on the right is likely to be several years old with significant deterioration illustrating the short term nature of this technique. Also note the gradual grade with the wedge on the left consistent with a grade of less than 8.3% and in keeping with the ADA draft guidelines for public right-of-ways.
Image 8: A wedge has been placed to mitigate the hazard caused by a raised sidewalk slab.
Image 9: A small wedge may still create a hazard or be difficult to navigate in a wheelchair.
This is a common and often effective repair when small sidewalk corners have broken off or minor gaps have formed between sidewalk panels. It is temporary and most often done in asphalt. When a concrete filler is used, it is best to undercut the hole to allow the patch to bond more permanently with the existing sidewalk. As seen below, patching (as well as wedging) leaves a lip that is at least as significant as the aggregate that is used in the material. Choosing asphalt as a patching and wedging material is seldom done in the southwest parts of the U.S. because of the incompatiability of the material with high sustained temperatures.
Image 10: Missing areas of concrete have been marked for repair.
Image 11: The areas have been temporarily repaired with asphalt patches.
Grinding and horizontal cutting are similar treatments. New cutting technology is allowing tighter tolerances with horizontal cutting saws. The photo on the left is of a horizontal cut at a sidewalk panel fault. Note that the panel has uniformly lifted allowing a straight cut across the width of the panel removing the tripping hazard. The panel being cut has not settled from one side to the other, just lengthwise. Therefore, there is no change in the cross slope, making cutting or grinding an appropriate treatment for this sidewalk displacement. Grinding or cutting of the panels depicted on the right will leave the transition between the panels without a tripping hazard, but will likely leave a warped condition as users transition to and from the treated area since the panel fault has settled to one side. A sidewalk with a cross slope greater than two % is not in compliance with ADA draft guidelines for public rights-of-way. ADA draft guidelines accept grinding and cutting for displacements of between ¼ in and ½ in. If over a ½ in, the repair has to be at the grade of a ramp – maximum of 8.3%.
Image 12: A raised sidewalk block has been ground down to provide a smoother transition.
Image 13: The diagram shows how an unevenly raised slab can be ground to provide a smoother transition.
This repair method lifts concrete sidewalk slabs back to their original position by pressure injecting cement or non-cement material under the sidewalk. Holes are drilled through the slab and grout is injected to raise the concrete slab or to fill the voids under them. Although it is less costly than replacement, it is only effective on sunken sidewalks. Of the communities contacted for this report, few were using this repair method. It can have long term success. The photo below of a mud-jacked sidewalk segment in Madison, Wisconsin, has been in good shape and in compliance to standards for more than 20 years.
Image 14: Graphic detail of how the mud-jacking process works.
Image 15: These panels were mud-jacked more than 20 years ago and are still in good condition.
Image 16: Replacement sidewalk being installed.
Photo Courtesy of the City of Charlotte
Although many repairs can provide temporary solutions to sidewalk problems, especially tripping hazards, at some point it becomes necessary to replace concrete sidewalks. This involves the entire removal and replacement of sidewalk panels or slabs and if done properly usually results in extending the life of sidewalks well over 10 years.
Of the communities contacted for this part of the research, there were several approaches in how communities used sidewalk replacement practices. One of models used especially in many of the Midwestern states was a zone-by-zone approach to sidewalk replacement. It is typically cost-effective for a moderately sized or larger community to manage an annual program for the replacement of sidewalks in a sub-area or zone of a community. Communities often put this in action on a four to 10 year cycle. It has the added benefit of being able to address all of the defects related to hazards and accessibility. Most communities combine this with short-term repairs as described above for addressing problems outside of the targeted zone(s) so that immediate hazards can still be addressed while a sidewalk replacement program is cycling through the city. Some of the smaller communities were able to manage such a program over the entire community on an annual basis. This model requires a significant commitment of inspection (see inspection and inventory).
Another model that was discovered when conducting discussions with communities was a sidewalk replacement program operated exclusively or nearly exclusively as the only means of sidewalk repair – none of the shorter term repairs cited above were used. Fifteen % of communities contacted for discussions used this approach including Norwalk, Iowa; Sparks, Nevada; Salisbury, North Carolina; Hoboken, New Jersey; Greenwich, Connecticut; Burlington, Vermont; Cedarburg, Wisconsin; and Crossville, Tennessee. Several in this group stated that they respond only to reported hazards on a community-wide basis and did not have a formal program in place where they had annual inspections and programmed replacements zone-by-zone. However, in these cases, their own city crews were replacing the sidewalks on the spot since these communities were funding 100% of the repairs. Not having to levy property assessments for these repairs significantly aided these communities ability to respond quickly to the hazards, and in some cases, they were replacing sidewalks in as few as three days to a week.
Nearly all of the communities reached for this study indicated that they take full advantage of street reconstruction projects to replace sidewalk pieces. At that time, cost for sidewalk replacement is generally at a lower unit cost.
The conditions of sidewalks for safe, comfortable and accessible travel are influenced by seasonal events such as snowfall, the accumulation of leaf debris and the overgrowth of vegetation. Maintenance activities to remove obstacles to safe walking are needed to keep sidewalks accessible and hazard-free year-round.
Meeting the obligations to keep sidewalks accessible is reinforced by the Americans with Disabilities Act (ADA).3 The act requires that to "the maximum extent feasible" pedestrian facilities in the public right-of-way be accessible to people with disabilities. The federal code acknowledges that there may be isolated or temporary interruptions in accessibility, but otherwise walking surfaces must be kept clear of snow, debris, and any obstructions to a minimum passage width of 36 inches.
The level of effort and cost associated with these activities varies widely between jurisdictions. Jurisdictions in different climatic zones have different seasonal activities. For example, jurisdictions in the "snow belt" must dedicate additional resources to snow removal while those with abundant street trees may require additional management of leaves and debris to ensure safe sidewalks. Throughout the United States, as conveyed by the communities researched, it is common that these activities are performed and balanced as part of an annual maintenance cycle. It is also common that local governments, by ordinance, pass on the responsibility of keeping sidewalks clear to the adjacent property owner abutting the sidewalk. This approach requires additional education, inspection, enforcement and administrative actions to be successful.
Street trees and other plants adjacent to the sidewalk are a beneficial amenity for a variety of reasons including provision of shade, carbon dioxide reduction, increased property value, stormwater control and visual interest. However, vegetation must be properly installed and maintained in order to keep the sidewalk unobstructed. Sightlines must also be maintained for pedestrian safety. In addition, the surface of the sidewalk must be kept free of debris. Most communities reported that work related to vegetation maintenance is not a significant effort due to the informal nature of most programs. However, jurisdictions with large numbers of deciduous street trees require leaf collection, and may require a significant seasonal maintenance effort.
Vegetation in the public right-of-way is often managed differently than vegetation that is planted on private property. The majority of communities surveyed require adjacent property owners to maintain vegetation on their parcels so that it does not overhang onto the sidewalk. Most jurisdictions found that this was a successful practice with good compliance. If vegetation is not maintained and it overhangs onto the sidewalk, many communities will follow-up only when complaints are filed. For example, the City of Greenwich, Connecticut, has an informal inspection program and complaints generally guide enforcement. Residents who have been notified of vegetation encroachment have 14 days to remove the vegetation. After 14 days the city will trim the vegetation for free. However, most residents comply because they do not want the city trimming their plants for aesthetic reasons. This process, although somewhat informal, has worked well to clear vegetation from adjacent sidewalks.
The City of Portland, Oregon, has developed a street tree program that equips residents with guidelines and information on how best to plant street trees. The pamphlet, which is available online, provides residents with spacing and planting information for the establishment of healthy trees. Other cities, such as Saint Paul and Minneapolis, Minnesota, encourage the planting of vegetation in the public right-of-way. A local organization has developed a "Twin Cities Boulevard Gardening" brochure that describes city guidelines such as vegetation height limits and location restrictions as well as the best materials to use for planter boxes.4 Providing the public with clear planting guidelines can encourage appropriate plantings in the public right-of-way, which can improve the stewardship of a community and help maintain a clear pedestrian zone free of obstructions.
Vegetation within the public right-of-way is managed in a variety of ways. Some communities require adjacent property owners to maintain vegetation planted between the sidewalk and the curb. Other jurisdictions may have city staff such as arborists, parks department personnel, public works personnel or urban foresters maintain city-owned street trees, which may include repairs to sidewalks when damaged by tree roots. Other jurisdictions require property owners to obtain a permit in order to plant between the sidewalk and the curb so that proper sightlines and the pedestrian clear zone are maintained. Successful programs employ arborists to do inspection, trimming and monitoring of construction activities that may influence street trees.
While some communities have ordinances regarding the maintenance of vegetation, it was unclear how many municipalities have ordinances that govern the maintenance of vegetation along the sidewalk on private property and in the public right-of-way. Wilsonville, Oregon, exemplifies the typical approach that small jurisdictions take toward vegetation maintenance. The city has one full-time arborist on staff in the public works department who is responsible for inspecting sidewalk vegetation overgrowth that impedes sightlines or sidewalk passage. If vegetation on private property has overgrown the sidewalk, the arborist will give the property owner notice to remove the vegetation. The city has the authority to remove the overgrowth and bill the property owner but that rarely occurs. Generally communities are less likely to enforce through fines than through the issuance of a warning.
The City of Seattle, a larger jurisdiction, has an Urban Forestry Department that is responsible for maintaining street trees. However, the street-use department manages enforcement of sidewalk overgrowth. Due to budgetary restrictions, the city has focused on educating property owners of their responsibilities rather than exercising enforcement mechanisms such as issuing tickets to property owners unless the conditions present a hazard.
In the presence of street trees, the success of sidewalk replacement and repair is determined by how well adjacent street trees are protected. Conversely, the health of street trees can be influenced by the maintenance and practices of sidewalk repairs. Factors that influence street tree health include: 1) adequate tree pit size for the tree type, 2) proper spacing along the roadway, and 3) making informed decisions when pruning and cutting roots.
Understanding the anatomy and special requirements of street trees and repairing sidewalks to best preserve existing trees can influence sidewalk conditions in the long-term. According to a presentation by James Kringer on urban forestry techniques presented as part of the UW-Madison's Developing an Effective Sidewalk Program, tree root systems extend horizontally one to two times the height of the tree and lie eight to 24 inches below the surface on average. Root systems are comprised of stabilizing roots and feeder roots. On average there are four to 11 stabilizing roots which are most likely to damage sidewalks. These roots extend horizontally from the trunk and provide stability and support for the tree. Cutting stabilizing roots can be detrimental to the health of the tree. Feeder roots are smaller and denser roots that absorb moisture and nutrients. These roots are less likely to be influenced by sidewalk repair.
There are several methods recommended to avoid damage to sidewalks and adjacent street trees. Each of these recommendations will be addressed in more detail in the final guide:
In communities with street trees and large amounts of street vegetation leaf collection can be a significant seasonal activity on the part of the jurisdiction. Surveyed communities reported spending between $10,000 and $200,000 annually on leaf and debris pick-up programs. Jurisdictions with leaf collection programs usually require residents to collect leaf and vegetation debris from adjacent properties, sidewalks, and gutters or sweep debris to the street for pick-up. Some communities dictate the collection techniques such as banning leaf blowers to reduce dust and noise pollution. Jurisdictions will then provide curbside pick-up on a weekly, monthly or seasonal basis. Some jurisdictions provide community composting opportunities in an effort to reduce costs of debris pick-up programs.
While most communities sweep streets of debris, only one community had an active city-wide, sidewalk-sweeping program. Many other jurisdictions have sidewalk debris removal programs within commercial business districts. For example, the City of Perry, GA, sweeps sidewalks in the core business district three times per year. Adjacent property owners or business improvement district contractors more commonly perform this work. The City of Concord, NH, sweeps sidewalks citywide every spring. The cost of the sidewalk sweeping program is approximately $15,000 annually. This activity clears sidewalks of accumulated debris remaining from snow removal.
3"2010 ADA Standards for Accessible Design – Alterations." U.S. Department of Justice. September 15, 2010. Accessed January 23, 2013. http://www.ada.gov/regs2010/2010ADAStandards/2010ADAstandards.htm#alterations.
4 "Twin Cities Boulevard Gardening." Sustainable Resources Center. Minneapolis. Accessed January 23, 2013. http://www.mppeace.org/downloads/boulevard.pdf.