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Support of excavation (soldier piles with timber lagging and tiebacks) at a site in Long Beach, CA. Photo credit: Rupert Price (SOCOTEC). |
- Demolition
- Underpinning
- Dewatering
- Excavation
- Drilling/Driving
The damages and risks associated with these activities described below are general and not intended to be comprehensive.
- Demolition and drilling/driving activities can cause excessive vibrations. The resulting damages, depending on the intensity of vibrations, can range from minor cracking in delicate plaster finishes to significant cracks in masonry walls. When cracks develop in the building envelope, water may infiltrate into the interior vastly increasing the extent of damage.
- Demolition is of particular concern when the building being demolished shares a party wall with the neighboring building. In those cases, care must be taken to ensure the stability and integrity of the remaining party wall or risk collapse.
- Drilling caissons is considered the more delicate operation compared to driving piles, a process in which the pile is hammered or vibrated into the ground. However, both drilling and driving send vibrations through the soil, which can cause them to shift and consolidate resulting in settlement of the adjacent building especially if prior soil loss has occurred. Differential settlement will cause a building to crack and/or lean.
- Excavations extending below the depth of the adjacent building’s foundations can cause that building to be undermined and at risk of collapse.
- To prevent that, some sort of support of excavation (SOE) is required. This could be a secant pile wall, soldier piles with timber lagging, or underpinning discussed in more detail below. SOE supports are driven or drilled along the perimeter of the excavation, which in these cases is abutting an adjacent building. They generally need to be braced laterally, either by rakers extending inward into the site or with tiebacks drilled into the soil or rock below the adjacent property. Rakers can be cumbersome to work around and require sequencing of construction activities around their eventual removal, so sites generally prefer to use tiebacks. The process of installing SOE can damage the adjacent property. Additionally, if the SOE is not designed or installed adequately, it can shift laterally causing the soils below the adjacent property to become loose. The exterior wall of the adjacent property may settle and shift causing the building to crack and/or lean.
- Underpinning is considered riskier than other forms of SOE. It is the process of extending an existing building’s foundation deeper into the ground by digging small pits that temporarily expose portions of the soil supporting the building’s foundations. The advantage of underpinning is that it allows the excavation and new construction to extend to the lot line. However, the underpinning is installed directly below the adjacent building’s exterior wall and some shifting of this wall may occur during the installation of underpinning. This could cause the building to crack and/or lean. It is also not uncommon for soil loss to occur in the process. Depending on how sensitive the structure is, soil loss during underpinning may cause settlement of slabs on grade and interior walls constructed on shallow foundations.
- Dewatering can compound the problem. A site must be dewatered if it has a water table higher than the lowest excavation depth. When a site is dewatered, the adjacent properties are also dewatered. When the groundwater is sucked out, sometimes the soil below the building gets sucked out along with it. And that soil, as previously discussed, is important.
Damage to adjacent properties can
result in costly repair, extensive delays, and sometimes even the evacuation of
the adjacent property and the permanent abandonment of the development
site.
Disputes between the development property and the adjacent property owner can commence before construction starts and continue well after construction has been completed.
1. The disputes begin with the negotiation of the access agreement. A confined construction site will often require access to the adjacent properties. Permission from the adjacent property owner is needed if underpinning and tiebacks are to be installed below grade within its property lines.
In some jurisdictions, such as New York City, the building department requires various protections for adjacent buildings including performing a pre-construction survey, installation of roof protection, and installation of various monitoring devices on the adjacent properties. The adjacent property owners can negotiate the terms under which access will be granted to developers to fulfill these requirements.
This is the adjacent property owner’s opportunity to insist on enhanced protective measures to prevent damage to its property and dictate how damage is addressed. The construction site will want to use the access to document all pre-existing damage to differentiate it from any new damage occurring during construction.
If the negotiation fails, the construction site can file for an injunction, but it may not be granted access to install underpinning and tiebacks.
Unfortunately, most construction sites do not at this stage develop a full understanding of the interior structure, the implications of the pre-existing damage, and the specific risks associated with this adjacent building. Do the signs of pre-existing settlement mean that the soils below the building are more susceptible and likely to move during drilling operations? Does the building have an inadequate lateral system that would make it more likely to lean and become destabilized? Would cracking or sloping of the slab on grade create an operational issue for a manufacturing facility that might result in shutdown and incur significant downtime costs?
2. Disputes continue through construction with complaints of damage and the enforcement of the access agreement. The adjacent property owner may complain of excessive vibrations, crack development, and other damage occurring throughout DUDED construction activities. If the damage is severe, the Department of Buildings (DOB) may get involved and issue a stop-work order. The DOB, however, will generally only act if there is a code violation or safety hazard, meaning it will not stop work because of non-hazardous damage to the adjacent structure. The battle related to non-hazardous damage is best waged by attorneys who should insist on the enforcement of the terms negotiated in the access agreement, which likely included terms requiring the site to alter its means and methods if established thresholds have been exceeded.
When resolved amicably, the contractor will immediately repair the damage it causes and take actions to reduce further damage.
The general contractor, however, will be concerned about meeting its schedule and the delay impact on all its subcontractors. The general contractor will want to push forward with construction without considering the cost implications of continuing to damage the adjacent structure.
3. Insurance claims, mediation, and litigation will continue long after the construction has been completed if the damages are not addressed amicably during construction. If the damage is covered by the adjacent property’s property insurance policy, the owner will submit a claim to its insurance company. Its insurance company will file a subrogation claim against the parties involved in the new construction.
If the owner does not feel it is being adequately compensated by its insurance policy, it may also directly sue the parties involved in the adjacent construction. Those parties usually include the developer, the general contractor, and each subcontractor involved in the DUDED activities. Those parties will issue claims to their general liability insurance carriers, and each insurance carrier will be involved in the dispute. The room quickly fills with lawyers and experts disputing the cause and cost of the damages incurred.
At the outset, they will compare the pre-existing conditions to the current conditions to establish what damage occurred during construction. However, the case gets more complicated when multiple parties performed potentially damaging activities within the timeframe during which the damage occurred.
To navigate these disputes,
you’ll need an engineering expert to review plans, advise on appropriate thresholds
for the various monitors, interpret and assess the recorded movements and
observable damage, and should litigation ensue, write a comprehensive cause and
origin report and possibly testify. A
good engineer can help you de-dud your DUDED project.
