How To Repair Sidewalk Lifted By Oak Tree

Options for Sidewalk Repair Effectually Existing Trees

Tree root-sidewalk conflicts are very common in developments. And the about commonly planted swale tree in many parts of Florida is the live oak (Quercus virginiana), which is a wonderful long-lived, sturdy tree, that only requires more root and body space than the half-dozen foot swale designated by the designers. And equally many homeowners and belongings managers take learned, the trouble seems to escalate later the start 10 years equally the trees brainstorm to mature and their root systems expand and try to grow out of the much-too-small infinite allotted between the street curb and the sidewalk.

Manifestly, it would be ameliorate to plant copse in larger spaces such as the front yard away from sidewalks and streets. But it is besides belatedly for many people who buy a home in a development that has already planted large-maturing copse in a narrow swale betwixt the sidewalk and the street. This is a landscape design flaw, in my stance, that is creating significant maintenance costs for homeowners and property managers.

Considering removal of the trees past sidewalks is not practical, sometimes not immune past local ordinance, and would remove an of import environmental amenity from streetscape, I will primarily talk over options to conform roots on existing big copse, infrastructure-based strategies, non options for recently planted young copse past sidewalks that we refer to as root-zone based strategies. The goal is to conform the infrastructure to accommodate the tree to reduce the sidewalk damage and increment the interval betwixt sidewalk repairs.

Types of impairment

Over the years we have observed swale trees (more often than not live oaks in this part of Florida) lifting sidewalks usually at the seam or expansion joint. The lifting can occur anywhere between the slab next to the trunk to as far away from the tree as the third concrete slab which is nearly 15 feet from the trunk. Once the slab lifts over ½ inch, there is a serious liability consequence — a trip and autumn hazard.

In addition to the lifting pressure caused past roots, the tree root flare of trees will slowly expand outward and even upwards putting sideways and up pressure on the sidewalk. Often the root flare begins to get a trouble with nearby infrastructure when trees reach a diameter of around 20 inches. The root flare of a thirty to 36 inch DBH live oak can extend almost the unabridged width of the 6-foot swale.

A slab has been removed and the existing roots are painted for identification.

Cut roots

We have institute that cutting roots is only a temporary solution. Severed roots regrow nether a sidewalk within iii years after being cut. In San Francisco and other cities, the interval betwixt root pruning and renewed sidewalk lifting is about five years. This relatively brusk repair interval can create an escalating and compounding effect of needed repairs equally the copse keep to abound.An boosted problem with root pruning is the loss of tree stability. Trees have stability against wind throw because of the lateral roots. Tap roots are rare and quite small in nearly broadleaf trees and provide virtually no support. When the important lateral roots are pruned, tree stability tin exist reduced. Research at the Bartlett Tree Research Laboratories has demonstrated that cutting large lateral roots within the root plate, which is a altitude from the trunk of three times the body diameter, tin can destabilize a tree. For example a 20-inch diameter tree should not have roots cutting closer than 60 inches from the tree (3 X twenty = threescore). In a 6-human foot broad swale with a growing tree, that does non allow space to root clip at the edge of the sidewalk. And then root pruning should only be done as a last resort when all other methods have been judged as not feasible. And those ordering cutting of major lateral roots should exist aware of the liability for tree failure that root cut creates. At that place are consequences to cutting roots such equally reduced tree health anddestabilization.

Other options

There are several options to consider when repairing lifted sidewalks. These include options that sometimes can be combined with others. All of the techniques except for #1 Shaving and #2 Slapjacking are used when removing and replacing sidewalk slabs.

Shaving lifted concrete: Once a slab is lifted by roots, it can be shaved downwards several times until the thickness of the sidewalk is also small to support the weight of pedestrians and golf game carts using the sidewalk. This relatively inexpensive technique should be used at first to even out lifted sidewalks. Another version of shaving is the utilise of cobblestone to level the sidewalk slabs where they accept lifted. Asphalt on a concrete sidewalk is not a very esthetic alternative.

Slabjacking: This is a process where concrete is injected under high pressure beneath the low side of a lifted slab causing the slab to elevator upwards to match the lifted section of the adjacent slab. This process has been around for several years but I accept yet to speak with anyone who has had the slapjacking washed.

Other options

Meandering sidewalk: Motion the repaired sidewalk out abroad from the tree by several feet preferably outside the root plate, which is the distance from the tree that is three times the tree bore.

Excavate beneath offending roots: Instead of cutting the offending roots that have lifted the sidewalk, leave the root intact and use an air excavation tool like an Air Spade or Air Pocketknife to remove soil beneath the root. This void can be left open beneath the root or filled with make clean pea gravel that volition move out of the way every bit the root expands downward. Because the concrete sidewalk is existence replaced above the root, the root should expand downwards filling the void. This technique should exist combined with reinforced sidewalks and possibly thicker sidewalks.

Span over roots: Sometimes the roots are too big to cutting and take expanded above the natural course. In these cases the root(s) must be bridged possibly creating a slight ascent in the sidewalk where it passes over the root.

Use reinforced physical: Utilise rebar or wire mesh when repouring physical sidewalk slabs. This will make the sidewalk stronger. Information technology is of import to connect the slabs together with rebar to avoid the lifting of a unmarried slab. In that style the root volition be pushing against two or three slabs rather than a single slab.

Use thicker physical: Increasing the concrete thickness from iv inches to half dozen inches will brand the sidewalk less probable to break or elevator. This technique should be used with the reinforced concrete technique higher up for best results. At that place is currently research beingness done to determine the best concrete thickness to utilize. Only no data is available at this time.

Place sidewalk over a geogrid and gravel base: Recent research into roots and sidewalks has demonstrated that a geogrid mesh base of operations placed on summit of roots will spread the force of the upwardly force per unit area of the roots over a broad area. Then if nosotros cover the geogrid with clean #57 rock for at least a depth of 3 to 4 inches, the physical sidewalk tin can be poured on top of the stone. The rock should be covered with a geotextile fabric to help keep the sand and soil from filtering into the stones, which provide a partially flexible buffer to diffuse the strength of lifting roots on the physical sidewalk slabs above. This arrangement may cause the sidewalk to be higher than the original sidewalk.

Place clean gravel below sidewalk: Contempo inquiry has demonstrated that simply placing clean gravel beneath a sidewalk slab will cause roots to abound below the gravel non directly beneath the concrete slab. The large air spaces in the gravel crusade whatever roots to grow below both the concrete sidewalk and the gravel layer. Consequently, the sidewalk is less probable to get pushed up past the roots.

Rubber Sidewalks and Pavers: Rubber sidewalks, other flexible materials and brick pavers allow for reduced repair costs to lift out a root-damaged sidewalk section and replace it. Notwithstanding, often the repair involves cut the offending root that is lifting the sidewalk. These materials, exercise not solve the trouble of what to exercise with an existing big root that is increasing in bore. Other methods may be needed to accommodate the large roots rather than cut them.

Other options that may not have merit

Pervious pavement: This type of pavement will let moisture to percolate through the concrete direct to the soil and roots below. But pervious physical is not as strong equally regular concrete so a thicker layer of pervious physical may exist needed. And allowing moisture to percolate through the physical may increment root growth beneath the concrete. Pervious concrete is a skillful product to use in a parking lot or area where root growth is to be encouraged and stimulated. Stimulating root growth under a sidewalk is not helping the situation, in my opinion.

Root Barriers: Root barriers are sometimes useful on well-drained soils on new plantings if the root barriers are properly installed and at least 2 or 3 anxiety deep. The peak of the root barrier must exist slightly above class or roots volition grow over the meridian of the barrier and this root barrier protruding edge tin can be cruddy. Proper installation is very important. Root barriers are usually not appropriate where trees are already established. For more on root barriers and recent root bulwark research click here.

Tree Growth Regulator (TGR) Applications: By and large arborists use TGR chemicals to tiresome summit growth of trees. Electric utilities have been using TGR'due south for over 30 years to command top growth of trees most power lines and extend the pruning cycle. Subsequently some arborists have been selling the relatively expensive TGR's as a way to reduce pruning and slow tree growth in developments where tree root-sidewalk conflicts are get-go to be a trouble. Ironically, the benefits of the most widely used TGR, paclobutrazol, is to divert energy from height growth into root growth. So TGR'due south may make the tree root-sidewalk conflict worse by increasing root growth even though top growth is being reduced. Until there is research indicating the TGR's are in reducing sidewalk damage or increasing the sidewalk repair interval, I do not recommend TGR's every bit a viable solution.

Heavy crown pruning to tiresome tree growth: The actress expense of heavy crown pruning to keep a large-growing tree curt and stunted is non really practical. Large maturing trees will chop-chop grow to their genetically predisposed size once the excessive and expensive pruning stops. In that location are many other reasons, which I will not become into hither, why heavy pruning will not work and is bad for the health of the trees.